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Scope keeps blowing fuses
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Cursitor Doom
Oct 22, 2022, 10:26:11 AM10/22/22
to
Hi all,
So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
main fuses (the 2A one on the rear panel). I opened the case and found
two RIFA caps that had obviously blown, so replaced them, but it's
still blowing fuses. I can't be 100% certain, but I'm pretty sure
there's a fault with the PSU board as I get the briefest whiff of
burning from that area each time I put a new fuse in and power up. The
new fuse blows again before I get to see any smoke coming from
anywhere at all. I'm linking to a diagram of the PSU as I'm not
familiar with this circuit topology. If anyone can spot a component
here that could have gone low-resistance and might be a good candidate
for out-of-circuit testing, by all means let me know.
Thanks,
CD.
https://disk.yandex.com/i/UhxATIy-6Y0LIA
So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
main fuses (the 2A one on the rear panel). I opened the case and found
two RIFA caps that had obviously blown, so replaced them, but it's
still blowing fuses. I can't be 100% certain, but I'm pretty sure
there's a fault with the PSU board as I get the briefest whiff of
burning from that area each time I put a new fuse in and power up. The
new fuse blows again before I get to see any smoke coming from
anywhere at all. I'm linking to a diagram of the PSU as I'm not
familiar with this circuit topology. If anyone can spot a component
here that could have gone low-resistance and might be a good candidate
for out-of-circuit testing, by all means let me know.
Thanks,
CD.
https://disk.yandex.com/i/UhxATIy-6Y0LIA
Peter W.
Oct 22, 2022, 11:08:27 AM10/22/22
to
Did the caps fail Open or Short?
Peter Wieck
Melrose Park, PA
Peter Wieck
Melrose Park, PA
ohg...@gmail.com
Oct 22, 2022, 11:57:09 AM10/22/22
to
Liz Tuddenham
Oct 22, 2022, 2:29:41 PM10/22/22
to
component is, but as a general principle my first suspects would be any
suppression capacitors across the incoming mains; they always seem to be
the first to go and they invariably fail short-ciircuit.
If the fuse is glass bodied with a simple wire element, the state of it
after it has blown will give you some idea of the type of fault. A dead
short will blacken the inside of the glass (and may break it), a
substantial overload will blow the wire to bits and leave blobs of metal
scattered around inside the glass, a prolonged gentle overload will
leave most of the wire intact but sagged and broken in the middle. This
may give you some idea of the sort of fault you are looking for and the
most likely place to find it.
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Cursitor Doom
Oct 22, 2022, 2:34:59 PM10/22/22
to
reason, they both failed open.
Cursitor Doom
Oct 22, 2022, 2:38:07 PM10/22/22
to
implementation here. Plus I can't probe the test points or look for
voltage drops when the power supply is constantly interrupted within
miliseconds of switch-on. Looks like I'll have to break out my dim
bulb tester (if I can find it).
Peter W.
Oct 22, 2022, 4:44:15 PM10/22/22
to
I am going to vote for C1001 & C1002. Either fails short and that fuse will blow. Both fail short and that blow will be instant. That or a bad primary winding - which could have been eaten by repeated refusing without proper diagnosis.
A dim-bulb tester is a reasonable tool for this purpose as a rubber spoon makes a reasonable carving knife. Just not fine enough for any kind of accurate diagnosis.
A dim-bulb tester is a reasonable tool for this purpose as a rubber spoon makes a reasonable carving knife. Just not fine enough for any kind of accurate diagnosis.
ehsjr
Oct 22, 2022, 5:01:05 PM10/22/22
to
Cursitor Doom
Oct 22, 2022, 5:03:04 PM10/22/22
to
On Sat, 22 Oct 2022 13:44:12 -0700 (PDT), "Peter W."
<peterw...@gmail.com> wrote:
>I am going to vote for C1001 & C1002. Either fails short and that fuse will blow. Both fail short and that blow will be instant. That or a bad primary winding - which could have been eaten by repeated refusing without proper diagnosis.
I don't see that as being an issue, though (the re-fusing bit) since
<peterw...@gmail.com> wrote:
>I am going to vote for C1001 & C1002. Either fails short and that fuse will blow. Both fail short and that blow will be instant. That or a bad primary winding - which could have been eaten by repeated refusing without proper diagnosis.
whatever has gone low-resistance is clearly drawing current away from
the other healthy components, no? And if said component has gone
low-res (as we assume it must) then cooking it a bit more doesn't
matter in the least since it's going to have to be replaced anyway.
The important thing is not to do it to such an extent that the PCB
becomes heat-damaged - in my submission anyway.
I'll check out the caps you suggested, however. Sounds like a good
call.
Thanks,
CD.
Cursitor Doom
Oct 22, 2022, 5:10:07 PM10/22/22
to
the wiring diagram I posted comes from. I find, however, that service
manuals in this form are so hard to navigate. I'd much rather have the
physical hard copy; so much more user-friendly.
three_jeeps
Oct 22, 2022, 7:34:53 PM10/22/22
to
I'd start by checking all the caps and semiconductors on the line side instead of continually smoke testing it. I wouldn't rule out the transformer either. Shouldn't be too hard to find. I'd also disconnect all the loads.
Perhaps the folks on the yahoo tek scopes group might have more targeted information - some sharp ppl there and all the do is scopes....
Good luck
Phil Allison
Oct 22, 2022, 9:58:52 PM10/22/22
to
Cursitor Doom wrote:
-------------------------------------
Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
.... Phil
-------------------------------------
> Hi all,
>
> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
> main fuses (the 2A one on the rear panel). I opened the case and found
> two RIFA caps that had obviously blown, so replaced them,
** Did both fail at the same time?
>
> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
> main fuses (the 2A one on the rear panel). I opened the case and found
> two RIFA caps that had obviously blown, so replaced them,
Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
.... Phil
st...@swingnn.com
Oct 23, 2022, 5:54:53 AM10/23/22
to
had a computer power supply that had four smoothing capacitors in
parallel. It worked with just one so all four had to fail before the
fault was detected.
--
Neural Network Software http://www.npsnn.com
JustNN Just a neural network http://www.justnn.com
EasyNN-plus More than just a neural network http://www.easynn.com
SwingNN Prediction software http://www.swingnn.com
Cursitor Doom
Oct 23, 2022, 6:21:38 AM10/23/22
to
able to unplug all the PSU outputs one by one until the bulb went out
(or went dim). That's on the alternative possibility that the fault
doesn't lie within the PSU board itself of course.
Phil Allison
Oct 23, 2022, 7:20:50 AM10/23/22
to
st...@swingnn.com wrote:
Phil Allison
-----------------
It sure as hell ain't smoothing...
....Phil
Phil Allison
-----------------
> >
> >
> >** Did both fail at the same time?
> >
> > Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
> >
> >.... Phil
>
> Two capacitors in parallel can cause a problem when they both fail. I
> had a computer power supply that had four smoothing capacitors in
> parallel. It worked with just one so all four had to fail before the
> fault was detected.
** So you have no clue what a piar of Rifa 68nF supreso caps do in an off line SMPS ?
> >
> >** Did both fail at the same time?
> >
> > Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
> >
> >.... Phil
>
> Two capacitors in parallel can cause a problem when they both fail. I
> had a computer power supply that had four smoothing capacitors in
> parallel. It worked with just one so all four had to fail before the
> fault was detected.
It sure as hell ain't smoothing...
....Phil
Peter W.
Oct 23, 2022, 7:54:52 AM10/23/22
to
It is already almost a certainty that the issue is in the power-supply. All that rubber spoon will tell you is that the issue is in the power-supply. At which point, you will need to troubleshoot at the component level.
Each time you apply power to what amounts to a dead-short, you may be damaging other components downline. When the second fuse blows, *STOP THERE*. Or the first, if there is any sort of associated symptoms such as heat, smoke, noise or a vaporized fuse.
Peter WIeck
Melrose Park, PA
Each time you apply power to what amounts to a dead-short, you may be damaging other components downline. When the second fuse blows, *STOP THERE*. Or the first, if there is any sort of associated symptoms such as heat, smoke, noise or a vaporized fuse.
Peter WIeck
Melrose Park, PA
Cursitor Doom
Oct 23, 2022, 8:11:39 AM10/23/22
to
On Sun, 23 Oct 2022 04:54:49 -0700 (PDT), "Peter W."
<peterw...@gmail.com> wrote:
>It is already almost a certainty that the issue is in the power-supply. All that rubber spoon will tell you is that the issue is in the power-supply. At which point, you will need to troubleshoot at the component level.
Well, I'm inclined to agree it's most likely in the PSU itself.
<peterw...@gmail.com> wrote:
>It is already almost a certainty that the issue is in the power-supply. All that rubber spoon will tell you is that the issue is in the power-supply. At which point, you will need to troubleshoot at the component level.
However, if it comes down to troubleshooting at component level then
I'm stuffed - certainly if I have to do it powered-up, because access
is very poor indeed on this model. On previous Tek scopes I've worked
on, it's been possible to pull the board out and work on it live
without much difficulty, but the 'plumbing-in' as it were of the
wiring on this one without some dedicated extender board is going to
be very challenging indeed.
>Each time you apply power to what amounts to a dead-short, you may be damaging other components downline. When the second fuse blows, *STOP THERE*. Or the first, if there is any sort of associated symptoms such as heat, smoke, noise or a vaporized fuse.
posted here and haven't attempted another power-up since.
Apart from the RIFAs, there's no sign of physical damage at all to the
other components. :-/
st...@swingnn.com
Oct 23, 2022, 8:31:15 AM10/23/22
to
Rifa are alone, in parallel or in series and can all fail at the same
time as can smoothing capacitors in parallel.
Cursitor Doom
Oct 23, 2022, 8:34:26 AM10/23/22
to
On Sun, 23 Oct 2022 13:31:10 +0100, st...@swingnn.com wrote:
>On Sun, 23 Oct 2022 04:20:47 -0700 (PDT), Phil Allison
><palli...@gmail.com> wrote:
>
>> st...@swingnn.com wrote:
>> Phil Allison
>>-----------------
>>> >
>>> >
>>> >** Did both fail at the same time?
>>> >
>>> > Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
>>> >
>>> >.... Phil
>>>
>>> Two capacitors in parallel can cause a problem when they both fail. I
>>> had a computer power supply that had four smoothing capacitors in
>>> parallel. It worked with just one so all four had to fail before the
>>> fault was detected.
>>
>>** So you have no clue what a piar of Rifa 68nF supreso caps do in an off line SMPS ?
>>
>> It sure as hell ain't smoothing...
>>
>>....Phil
>>
>
>I was pointing out a common misunderstanding with multiple capacitors.
>Rifa are alone, in parallel or in series and can all fail at the same
>time as can smoothing capacitors in parallel.
That's a bit misleading and it's de-railing the thread.
>On Sun, 23 Oct 2022 04:20:47 -0700 (PDT), Phil Allison
><palli...@gmail.com> wrote:
>
>> st...@swingnn.com wrote:
>> Phil Allison
>>-----------------
>>> >
>>> >
>>> >** Did both fail at the same time?
>>> >
>>> > Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
>>> >
>>> >.... Phil
>>>
>>> Two capacitors in parallel can cause a problem when they both fail. I
>>> had a computer power supply that had four smoothing capacitors in
>>> parallel. It worked with just one so all four had to fail before the
>>> fault was detected.
>>
>>** So you have no clue what a piar of Rifa 68nF supreso caps do in an off line SMPS ?
>>
>> It sure as hell ain't smoothing...
>>
>>....Phil
>>
>
>I was pointing out a common misunderstanding with multiple capacitors.
>Rifa are alone, in parallel or in series and can all fail at the same
>time as can smoothing capacitors in parallel.
Peter W.
Oct 23, 2022, 8:34:33 AM10/23/22
to
a) Do you have a VOM? And, if so, how good is it?
b) Not that testing capacitors in-situ generally accurate, but you can usually tell the difference between an open cap and a dead-shorted cap using the Ohms scale.
c) Similarly, transistors.
d) And it is possible that the RIFAs were symptoms, not the cause.
Which would be a start.
b) Not that testing capacitors in-situ generally accurate, but you can usually tell the difference between an open cap and a dead-shorted cap using the Ohms scale.
c) Similarly, transistors.
d) And it is possible that the RIFAs were symptoms, not the cause.
Which would be a start.
Cursitor Doom
Oct 23, 2022, 8:47:58 AM10/23/22
to
On Sun, 23 Oct 2022 05:34:30 -0700 (PDT), "Peter W."
<peterw...@gmail.com> wrote:
>a) Do you have a VOM? And, if so, how good is it?
Several! Some professional ones too.
<peterw...@gmail.com> wrote:
>a) Do you have a VOM? And, if so, how good is it?
>b) Not that testing capacitors in-situ generally accurate, but you can usually tell the difference between an open cap and a dead-shorted cap using the Ohms scale.
>c) Similarly, transistors.
>d) And it is possible that the RIFAs were symptoms, not the cause.
if they blew together or seperately. I can say is that they both went
catastrophically and blasted crap all over the surrounding components.
But we all know these caps 'let go' after a certain time in service
anyway. You can pretty much guarantee it.
>
>Which would be a start.
layout of the PSU on this model is just awful. Just one example, they
didn't leave enough room for the board! it's tight interference fit
with the casing and can only be withdrawn and inserted with
considerable force.
Peter W.
Oct 23, 2022, 12:36:27 PM10/23/22
to
If the alternative is landfill, then heroic measures are justified.
If the alternative is 'sending it out', unless you wish to did deeper - and all indications are that you do not - then go ahead and send it out.
There is no magic bullet.
If the alternative is 'sending it out', unless you wish to did deeper - and all indications are that you do not - then go ahead and send it out.
There is no magic bullet.
Cursitor Doom
Oct 23, 2022, 12:59:04 PM10/23/22
to
On Sun, 23 Oct 2022 09:36:24 -0700 (PDT), "Peter W."
<peterw...@gmail.com> wrote:
>If the alternative is landfill, then heroic measures are justified.
I totally get where you're coming from here.
<peterw...@gmail.com> wrote:
>If the alternative is landfill, then heroic measures are justified.
>If the alternative is 'sending it out', unless you wish to did deeper - and all indications are that you do not - then go ahead and send it out.
with this scope that will most likely still be present even if the
present one is fixed. In fact, this 'other fault' may well have caused
the current one. This 'other fault' involved the displayed traces
suddenly turning extremely bright, accompanied by lines of dots. It
materialised only rarely, but I was out of the room when the scope
went *phut* so have no idea if there's any link to the current fault
or not.
I'm beginning to suspect those caps may have failed at some time in
the past, because for them to go *bang* with that amount of crap
sprayed everywhere must surely have resulted in a great deal of acrid
smoke being released - yet there was none discernable. And if those
caps fail open circuit (which they both did despite being X2 safety
ones which are supposed to fail short) then the scope can contintue to
function pretty well as normal so long as the mains supply is
reasonably clean.
>There is no magic bullet.
Jeff Liebermann
Oct 23, 2022, 2:16:29 PM10/23/22
to
On Sat, 22 Oct 2022 15:26:04 +0100, Cursitor Doom <c...@notformail.com>
wrote:
>Hi all,
Bah Humbug.
>So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
>main fuses (the 2A one on the rear panel).
"Oscilloscope Restoration Project - Repair Tektronix 2465B 400MHz"
<https://cdn.hackaday.io/files/1638907011869760/Tektronix-2465A-B-Oscilloscope-Restoration-Repair.pdf>
"Symptoms: This is my lab unit, which suddenly started blowing its
main AC fuse."
"Amazing Tektronix 2465 Repair Information"
<https://jestineyong.com/amazing-tektronix-2465-repair-information/>
Concerning my Tektronix 2465 repair I yesterday
replaced both 0.068uF 250VAC caps after I had
received the ordered new 275VAC caps.
Both caps are C1016 and C1018 in the Tektronix
service manual schematic on Board A2A1. And
only the C1016 0.068uF capacitor had blown
which also damaged the serie resistor R1016
of 68 ohm 5% which also was replaced.
They protect the Diode Bridge CR1011 (600V
3A Fast Recovery type RKBPC606-12) against
damage by high AC power voltages. The Diode
Bridge was not damaged. My oscilloscope is
happily working as new again. (48019 HRS of
service in 32 years or so).
Good luck.
--
Jeff Liebermann je...@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
wrote:
>Hi all,
Bah Humbug.
>So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
>main fuses (the 2A one on the rear panel).
<https://cdn.hackaday.io/files/1638907011869760/Tektronix-2465A-B-Oscilloscope-Restoration-Repair.pdf>
"Symptoms: This is my lab unit, which suddenly started blowing its
main AC fuse."
"Amazing Tektronix 2465 Repair Information"
<https://jestineyong.com/amazing-tektronix-2465-repair-information/>
Concerning my Tektronix 2465 repair I yesterday
replaced both 0.068uF 250VAC caps after I had
received the ordered new 275VAC caps.
Both caps are C1016 and C1018 in the Tektronix
service manual schematic on Board A2A1. And
only the C1016 0.068uF capacitor had blown
which also damaged the serie resistor R1016
of 68 ohm 5% which also was replaced.
They protect the Diode Bridge CR1011 (600V
3A Fast Recovery type RKBPC606-12) against
damage by high AC power voltages. The Diode
Bridge was not damaged. My oscilloscope is
happily working as new again. (48019 HRS of
service in 32 years or so).
Good luck.
--
Jeff Liebermann je...@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
whit3rd
Oct 23, 2022, 5:13:32 PM10/23/22
to
On Saturday, October 22, 2022 at 7:26:11 AM UTC-7, Cursitor Doom wrote:
> Hi all,
>
> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
> main fuses (the 2A one on the rear panel). I opened the case and found
> two RIFA caps that had obviously blown, so replaced them, but it's
> still blowing fuses. I can't be 100% certain, but I'm pretty sure
> there's a fault with the PSU board as I get the briefest whiff of
> burning from that area each time I put a new fuse in and power up.
First thing to check is the rectifier; that diode bridge can fail, and
> Hi all,
>
> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
> main fuses (the 2A one on the rear panel). I opened the case and found
> two RIFA caps that had obviously blown, so replaced them, but it's
> still blowing fuses. I can't be 100% certain, but I'm pretty sure
> there's a fault with the PSU board as I get the briefest whiff of
> burning from that area each time I put a new fuse in and power up.
apply AC to the filter capacitors, and... that'll take out the fuse.
Not sure why the RIFA capa goes, though; maybe just a power surge some
time last week?
There seem to be some surge-suppressors (gas discharge?) in the diagram, they might
have failed short in a surge..
Cursitor Doom
Oct 23, 2022, 5:56:30 PM10/23/22
to
On Sun, 23 Oct 2022 14:13:30 -0700 (PDT), whit3rd <whi...@gmail.com>
wrote:
Yes, they're each showing about 70k ohms, so can't be responsible.
One thing I forgot to mention in my first post was that a wire had
come adrift from the cooling fan's supply (poor factory soldering
clearly) so this unit had been running for an unknown length of time
with no fan. Not sure if that's relevant to the fault here, but it
certainly *could* be....
wrote:
One thing I forgot to mention in my first post was that a wire had
come adrift from the cooling fan's supply (poor factory soldering
clearly) so this unit had been running for an unknown length of time
with no fan. Not sure if that's relevant to the fault here, but it
certainly *could* be....
Cursitor Doom
Oct 23, 2022, 5:57:50 PM10/23/22
to
On Sun, 23 Oct 2022 11:16:19 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:
>On Sat, 22 Oct 2022 15:26:04 +0100, Cursitor Doom <c...@notformail.com>
>wrote:
>
>>Hi all,
>
>Bah Humbug.
>
>>So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
>>main fuses (the 2A one on the rear panel).
>
>"Oscilloscope Restoration Project - Repair Tektronix 2465B 400MHz"
><https://cdn.hackaday.io/files/1638907011869760/Tektronix-2465A-B-Oscilloscope-Restoration-Repair.pdf>
>"Symptoms: This is my lab unit, which suddenly started blowing its
>main AC fuse."
>
>"Amazing Tektronix 2465 Repair Information"
><https://jestineyong.com/amazing-tektronix-2465-repair-information/>
>
>Good luck
Thanks for the links, Jeff; I'll check 'em out...
wrote:
>On Sat, 22 Oct 2022 15:26:04 +0100, Cursitor Doom <c...@notformail.com>
>wrote:
>
>>Hi all,
>
>Bah Humbug.
>
>>So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
>>main fuses (the 2A one on the rear panel).
>
>"Oscilloscope Restoration Project - Repair Tektronix 2465B 400MHz"
><https://cdn.hackaday.io/files/1638907011869760/Tektronix-2465A-B-Oscilloscope-Restoration-Repair.pdf>
>"Symptoms: This is my lab unit, which suddenly started blowing its
>main AC fuse."
>
>"Amazing Tektronix 2465 Repair Information"
><https://jestineyong.com/amazing-tektronix-2465-repair-information/>
>
Thanks for the links, Jeff; I'll check 'em out...
Phil Allison
Oct 23, 2022, 7:41:08 PM10/23/22
to
st...@swingnn.com wrote:
----------------------------------------------
Phil Allison
......Phil
----------------------------------------------
Phil Allison
>
> >> >** Did both fail at the same time?
> >> >
> >> > Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
> >> >
> >> >.... Phil
> >>
> >> Two capacitors in parallel can cause a problem when they both fail. I
> >> had a computer power supply that had four smoothing capacitors in
> >> parallel. It worked with just one so all four had to fail before the
> >> fault was detected.
> >
> >** So you have no clue what a piar of Rifa 68nF supreso caps do in an off line SMPS ?
> >
> > It sure as hell ain't smoothing...
> >
>
> >> >** Did both fail at the same time?
> >> >
> >> > Those Rifa caps are bound to self destruct at some age, but two at once is suspicious.
> >> >
> >> >.... Phil
> >>
> >> Two capacitors in parallel can cause a problem when they both fail. I
> >> had a computer power supply that had four smoothing capacitors in
> >> parallel. It worked with just one so all four had to fail before the
> >> fault was detected.
> >
> >** So you have no clue what a piar of Rifa 68nF supreso caps do in an off line SMPS ?
> >
> > It sure as hell ain't smoothing...
> >
>
> I was pointing out a common misunderstanding with multiple capacitors.
> Rifa are alone, in parallel or in series and can all fail at the same
> time as can smoothing capacitors in parallel.
** Shame how you own example contradict that idea.
> Rifa are alone, in parallel or in series and can all fail at the same
> time as can smoothing capacitors in parallel.
......Phil
Phil Allison
Oct 23, 2022, 7:46:51 PM10/23/22
to
Cursitor Doom wrote:
---------------------------------
Plenty are found open or with low values after long times in service.
X2 dropping caps used in smoke alarms regularly fail open.
But those Rifa ones love to smoke and burn.
.......Phil
---------------------------------
> And if those
> caps fail open circuit (which they both did despite being X2 safety
> ones which are supposed to fail short)
** Really ? Where did you get that idea?
> caps fail open circuit (which they both did despite being X2 safety
> ones which are supposed to fail short)
Plenty are found open or with low values after long times in service.
X2 dropping caps used in smoke alarms regularly fail open.
But those Rifa ones love to smoke and burn.
.......Phil
Jeff Liebermann
Oct 23, 2022, 8:14:05 PM10/23/22
to
Tektronix scopes and RIFA caps:
"Old RIFA capacitors and a disaster story"
<https://www.eevblog.com/forum/chat/old-rifa-capacitors-and-a-disaster-story/>
YouTube videos featuring smoking RIFA caps:
<https://www.youtube.com/results?search_query=rifa+capacitor>
I sometimes test the HV leakage in capacitors using an ancient Megger:
<http://www.learnbydestroying.com/jeffl/pics/Megger/Megger-Major.jpg>
<https://www.vintage-radio.net/forum/showthread.php?t=73265>
Unsolder the capacitor for testing. You really don't want a high
voltage power source connected to your oscilloscope.
legg
Oct 24, 2022, 9:28:50 AM10/24/22
to
>So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
>main fuses (the 2A one on the rear panel). I opened the case and found
>two RIFA caps that had obviously blown, so replaced them, but it's
>still blowing fuses. I can't be 100% certain, but I'm pretty sure
>there's a fault with the PSU board as I get the briefest whiff of
>two RIFA caps that had obviously blown, so replaced them, but it's
>still blowing fuses. I can't be 100% certain, but I'm pretty sure
>there's a fault with the PSU board as I get the briefest whiff of
>burning from that area each time I put a new fuse in and power up. The
>new fuse blows again before I get to see any smoke coming from
>anywhere at all. I'm linking to a diagram of the PSU as I'm not
>familiar with this circuit topology. If anyone can spot a component
>here that could have gone low-resistance and might be a good candidate
>for out-of-circuit testing, by all means let me know.
>Thanks,
>
>CD.
>
>
>https://disk.yandex.com/i/UhxATIy-6Y0LIA
Don't know your line voltage, but if it's 240, check the
>new fuse blows again before I get to see any smoke coming from
>anywhere at all. I'm linking to a diagram of the PSU as I'm not
>familiar with this circuit topology. If anyone can spot a component
>here that could have gone low-resistance and might be a good candidate
>for out-of-circuit testing, by all means let me know.
>Thanks,
>
>CD.
>
>
>https://disk.yandex.com/i/UhxATIy-6Y0LIA
input voltage setting on the scope.
If RFI caps are replaced and bridge is ok, check big
electros (C1021, C1022) and main switch (Q1050) for
shorts.
At 240V, a leaky bulk cap can blow the gas tubes.
Once a gas tube fires, it's breakover voltage will
reduce, so must be replaced, too.
RL
legg
Oct 24, 2022, 9:45:21 AM10/24/22
to
On Sun, 23 Oct 2022 17:13:54 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:
>On Sun, 23 Oct 2022 16:46:49 -0700 (PDT), Phil Allison
><palli...@gmail.com> wrote:
>
>> Cursitor Doom wrote:
>>---------------------------------
>>> And if those
>>> caps fail open circuit (which they both did despite being X2 safety
>>> ones which are supposed to fail short)
>
>>** Really ? Where did you get that idea?
>>
>>Plenty are found open or with low values after long times in service.
>>X2 dropping caps used in smoke alarms regularly fail open.
>>
>>But those Rifa ones love to smoke and burn.
>>
>>.......Phil
>
>RIFA caps smoke, especially the old ones. This is typical for vintage
>Tektronix scopes and RIFA caps:
>
>"Old RIFA capacitors and a disaster story"
><https://www.eevblog.com/forum/chat/old-rifa-capacitors-and-a-disaster-story/>
>
>YouTube videos featuring smoking RIFA caps:
><https://www.youtube.com/results?search_query=rifa+capacitor>
>
>I sometimes test the HV leakage in capacitors using an ancient Megger:
><http://www.learnbydestroying.com/jeffl/pics/Megger/Megger-Major.jpg>
><https://www.vintage-radio.net/forum/showthread.php?t=73265>
>Unsolder the capacitor for testing. You really don't want a high
>voltage power source connected to your oscilloscope.
The smoking caps were metalized paper construction. These were good
enough in their day, with a demonstrated mtbf and safe self-healing,
while seals lasted. The outer sealing body tended to shrink and crack
with age, allowing ingress of air and moisture, compromising
performance. They are no longer made.
Metalized film parts are usually less dramatic in self-clearing
of internal faults, but in extreme cases, you still get thermal
runaway, as the faulting area expands and eats away at succesive
layers of the wrapped structure.
Film parts will generally fail at the end schoopage joint, where
metalization and film stresses accumulate in mfring.
RL
wrote:
>On Sun, 23 Oct 2022 16:46:49 -0700 (PDT), Phil Allison
><palli...@gmail.com> wrote:
>
>> Cursitor Doom wrote:
>>---------------------------------
>>> And if those
>>> caps fail open circuit (which they both did despite being X2 safety
>>> ones which are supposed to fail short)
>
>>** Really ? Where did you get that idea?
>>
>>Plenty are found open or with low values after long times in service.
>>X2 dropping caps used in smoke alarms regularly fail open.
>>
>>But those Rifa ones love to smoke and burn.
>>
>>.......Phil
>
>RIFA caps smoke, especially the old ones. This is typical for vintage
>Tektronix scopes and RIFA caps:
>
>"Old RIFA capacitors and a disaster story"
><https://www.eevblog.com/forum/chat/old-rifa-capacitors-and-a-disaster-story/>
>
>YouTube videos featuring smoking RIFA caps:
><https://www.youtube.com/results?search_query=rifa+capacitor>
>
>I sometimes test the HV leakage in capacitors using an ancient Megger:
><http://www.learnbydestroying.com/jeffl/pics/Megger/Megger-Major.jpg>
><https://www.vintage-radio.net/forum/showthread.php?t=73265>
>Unsolder the capacitor for testing. You really don't want a high
>voltage power source connected to your oscilloscope.
enough in their day, with a demonstrated mtbf and safe self-healing,
while seals lasted. The outer sealing body tended to shrink and crack
with age, allowing ingress of air and moisture, compromising
performance. They are no longer made.
Metalized film parts are usually less dramatic in self-clearing
of internal faults, but in extreme cases, you still get thermal
runaway, as the faulting area expands and eats away at succesive
layers of the wrapped structure.
Film parts will generally fail at the end schoopage joint, where
metalization and film stresses accumulate in mfring.
RL
Charles Lucas
Oct 24, 2022, 1:12:04 PM10/24/22
to
Hi, everyone (including the original poster).
When the power supply unit fails, there can be a basic myriad of possible problems
and/or failed components.
Here are some things to look for:
Current limiting resistors, rectifier diodes, transformers, transistors,
caps., filters, coils, etc... Shorts and opens are common problems. Look
for bad connections, cold solders, etc... Lots to check for to "pin in down".
Especially with older devices. Since it is an analog device (as was said),
it is assumed the equipment is old, so we have to go to the old school
way of checking everything, looking for key things, in order to come up
with some accurate diagnosis.
Good luck and have a great day.
Charles Lucas
When the power supply unit fails, there can be a basic myriad of possible problems
and/or failed components.
Here are some things to look for:
Current limiting resistors, rectifier diodes, transformers, transistors,
caps., filters, coils, etc... Shorts and opens are common problems. Look
for bad connections, cold solders, etc... Lots to check for to "pin in down".
Especially with older devices. Since it is an analog device (as was said),
it is assumed the equipment is old, so we have to go to the old school
way of checking everything, looking for key things, in order to come up
with some accurate diagnosis.
Good luck and have a great day.
Charles Lucas
three_jeeps
Oct 24, 2022, 1:29:55 PM10/24/22
to
What is the recommended replacement type? (assuming they can physically fit into the same space on the board)
I have a few vintage Tek scopes that I should do some preventative maintenance work on....
J
Jeff Liebermann
Oct 24, 2022, 1:35:31 PM10/24/22
to
capacitors the show some leakage for maybe 250 msec and then recover.
I've been assuming that this demonstrates that self healing is
function. Known good capacitors don't do that. Since testing
required removing the capacitor from the PCB, I just replace any
capacitor that shows temporary leakage. (i.e. better safe than
sorry).
This video shows what might be two self healing RIFA capacitors in
action. Watch the current on the display:
"40 Year Old Rifa Capacitors High Voltage Leakage Testing"
<https://www.youtube.com/watch?v=m1nDrunJ1SE> (3:09)
The effect is more visible with a panel meter than with a digital
readout (except when the meter is moving because I'm turning the crank
on the Megger).
>Metalized film parts are usually less dramatic in self-clearing
>of internal faults, but in extreme cases, you still get thermal
>runaway, as the faulting area expands and eats away at succesive
>layers of the wrapped structure.
have several suitable microscopes and would expect to find holed in
the dielectric (paper or plastic) and the metalization. The RIVA caps
that failed have warped, cracked, melted, or crumbled outer plastic
cases. For meaningful microscopy, I would need an old RIFA capacitor
in an intact case.
>Film parts will generally fail at the end schoopage joint, where
>metalization and film stresses accumulate in mfring.
>
>RL
Jeff Liebermann
Oct 24, 2022, 2:10:21 PM10/24/22
to
>I know about the RIFA caps exploding - thanks for the interesting video tho.
>What is the recommended replacement type? (assuming they can physically fit into the same space on the board)
>I have a few vintage Tek scopes that I should do some preventative maintenance work on....
>J
"RIFA - Replacement Choices"
>What is the recommended replacement type? (assuming they can physically fit into the same space on the board)
>I have a few vintage Tek scopes that I should do some preventative maintenance work on....
>J
<https://www.eevblog.com/forum/beginners/rifa-replacement-choices/>
Kemet bought RIFA. My older Tek scopes survive 30 to 40 years and
usually blow electroltyics before RIFA caps. Rather than experiment,
I simply bought the same value/voltage X2 "safety" caps from Kemet
(via Mouser or Digikey):
<https://www.kemet.com/en/us/capacitors/film/safety.html?40=133>
I wasn't very careful when I ordered replacement caps many years ago.
I think I ordered "metalized paper", which in retrospect, was not the
best choice. Going down the list of dielectrics, only "metalized
paper" and "metalized polypropylene" are available for "safety" caps.
Kemet is recommending their R53 X2 caps with "metalized polypropylene
film" dielectric.
<https://www.mouser.com/new/kemet-electronics/kemet-miniature-emi-suppression-capacitors/>
<https://www.digikey.com/en/product-highlight/k/kemet/r53-film-capacitors>
X2 is for "line to line" filtering while Y2 is for "line to ground"
filtering.
Peter W.
Oct 24, 2022, 2:12:12 PM10/24/22
to
OK.
What is known:
a) Scope is blowing mains fuses.
b) RIFA -branded caps blew up.
c) The power-supply board was affected.
Suggestion:
1) Remove the power-supply board.
2) Replace all, repeat: ALL the capacitors on that board of any nature, type or style with the correct (but modern) replacement type.
3) Check each other component on the board. Diodes, regulators, transistors, whatever.
4) Replace any that are either bad or the slightest bit questionable.
5) Replace board - carefully (now might be an opportunity for a DBT to 'do its thing' - but a metered Variac would be better).
I kinda-sorta think that will do it. KISS and all that.
What is known:
a) Scope is blowing mains fuses.
b) RIFA -branded caps blew up.
c) The power-supply board was affected.
Suggestion:
1) Remove the power-supply board.
2) Replace all, repeat: ALL the capacitors on that board of any nature, type or style with the correct (but modern) replacement type.
3) Check each other component on the board. Diodes, regulators, transistors, whatever.
4) Replace any that are either bad or the slightest bit questionable.
5) Replace board - carefully (now might be an opportunity for a DBT to 'do its thing' - but a metered Variac would be better).
I kinda-sorta think that will do it. KISS and all that.
Jeff Liebermann
Oct 24, 2022, 3:06:26 PM10/24/22
to
On Sun, 23 Oct 2022 11:16:19 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:
(chomp...)
When in doubt, replace everything.
I was wondering if someone sells a recap kit for the Tek 2465. Yep:
<https://www.ebay.com/itm/313637931679>
It includes some RIFA -> Kemet replacement caps.
wrote:
(chomp...)
When in doubt, replace everything.
I was wondering if someone sells a recap kit for the Tek 2465. Yep:
<https://www.ebay.com/itm/313637931679>
It includes some RIFA -> Kemet replacement caps.
Cursitor Doom
Oct 24, 2022, 5:10:18 PM10/24/22
to
On Mon, 24 Oct 2022 11:10:12 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:
Jeff, remind me to post a picture of the cap replacement I've carried
out. You'll be both horrified and astounded. If I had more time I'd
post it now, but it'll have to wait for the time being..
wrote:
out. You'll be both horrified and astounded. If I had more time I'd
post it now, but it'll have to wait for the time being..
Cursitor Doom
Oct 24, 2022, 5:18:03 PM10/24/22
to
current limiting, as the bulb can react to sudden over-current much
more quickly than I can. I'll slowly bring the variac up whilst
checking for anything getting warm on the board. That's the best I can
manage as I'm no tech repairer; haven't got the necessary fine motor
skills, I'm afraid.
Jeff Liebermann
Oct 24, 2022, 7:53:08 PM10/24/22
to
On Mon, 24 Oct 2022 22:17:57 +0100, Cursitor Doom <c...@notformail.com>
wrote:
>I'm no tech repairer; haven't got the necessary fine motor
>skills, I'm afraid.
Not a problem. Let a hand soldering robot do the precision work.
Something like this soldering robot:
<https://www.promationusa.com/9101>
More:
<https://www.promationusa.com/robotic-soldering-glance>
and even more:
<https://www.google.com/search?q=hand+soldering+robot&tbm=isch>
wrote:
>I'm no tech repairer; haven't got the necessary fine motor
>skills, I'm afraid.
Something like this soldering robot:
<https://www.promationusa.com/9101>
More:
<https://www.promationusa.com/robotic-soldering-glance>
and even more:
<https://www.google.com/search?q=hand+soldering+robot&tbm=isch>
Phil Allison
Oct 24, 2022, 8:21:03 PM10/24/22
to
legg wrote:
------------------
Strangely they are also the most expensive X2 caps on offer for no good reason.
Described as being of "metalised , impregnated paper " construction.
Rifa also claim to be the only supplier .
Other makers, dozens of them, use metalised polyester or polypropylene films as used in DC rated caps - but with one big difference.
X2 types are double wound = a technique that creates two caps in series.
Such caps are immune from *corona discharge* occurring in tiny air pockets trapped inside the cap as it it being wound.
They are still vulnerable to spike voltages of a few kV which eat away at metalisation and reduce cap value over time.
IME Rifa X2s are notorious for catching fire and filling the room with acrid smoke.
Happened twice, right in front of me, first case was a room heater and the second with a portable TV.
When used for suppression in triac dimming equipment, they invariably fail early too.
Bad news.
..... Phil
------------------
> >
> >> Cursitor Doom wrote:
> >>---------------------------------
> >>> And if those
> >>> caps fail open circuit (which they both did despite being X2 safety
> >>> ones which are supposed to fail short)
> >
> >>** Really ? Where did you get that idea?
> >>
> >>Plenty are found open or with low values after long times in service.
> >>X2 dropping caps used in smoke alarms regularly fail open.
> >>
> >>But those Rifa ones love to smoke and burn.
> >>
==================================================
> >> Cursitor Doom wrote:
> >>---------------------------------
> >>> And if those
> >>> caps fail open circuit (which they both did despite being X2 safety
> >>> ones which are supposed to fail short)
> >
> >>** Really ? Where did you get that idea?
> >>
> >>Plenty are found open or with low values after long times in service.
> >>X2 dropping caps used in smoke alarms regularly fail open.
> >>
> >>But those Rifa ones love to smoke and burn.
> >>
>
> The smoking caps were metalized paper construction. These were good
> enough in their day, with a demonstrated mtbf and safe self-healing,
> while seals lasted. The outer sealing body tended to shrink and crack
> with age, allowing ingress of air and moisture, compromising
> performance. They are no longer made.
** Rifa PME271 X2 caps are still made and widely available.
> The smoking caps were metalized paper construction. These were good
> enough in their day, with a demonstrated mtbf and safe self-healing,
> while seals lasted. The outer sealing body tended to shrink and crack
> with age, allowing ingress of air and moisture, compromising
> performance. They are no longer made.
Strangely they are also the most expensive X2 caps on offer for no good reason.
Described as being of "metalised , impregnated paper " construction.
Rifa also claim to be the only supplier .
Other makers, dozens of them, use metalised polyester or polypropylene films as used in DC rated caps - but with one big difference.
X2 types are double wound = a technique that creates two caps in series.
Such caps are immune from *corona discharge* occurring in tiny air pockets trapped inside the cap as it it being wound.
They are still vulnerable to spike voltages of a few kV which eat away at metalisation and reduce cap value over time.
IME Rifa X2s are notorious for catching fire and filling the room with acrid smoke.
Happened twice, right in front of me, first case was a room heater and the second with a portable TV.
When used for suppression in triac dimming equipment, they invariably fail early too.
Bad news.
..... Phil
Phil Hobbs
Oct 24, 2022, 8:38:07 PM10/24/22
to
Cursitor Doom wrote:
> Hi all,
>
> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
> main fuses (the 2A one on the rear panel). I opened the case and found
> two RIFA caps that had obviously blown, so replaced them, but it's
> still blowing fuses. I can't be 100% certain, but I'm pretty sure
> there's a fault with the PSU board as I get the briefest whiff of
> burning from that area each time I put a new fuse in and power up. The
> new fuse blows again before I get to see any smoke coming from
> anywhere at all. I'm linking to a diagram of the PSU as I'm not
> familiar with this circuit topology. If anyone can spot a component
> here that could have gone low-resistance and might be a good candidate
> for out-of-circuit testing, by all means let me know.
> Thanks,
>
> CD.
>
>
> https://disk.yandex.com/i/UhxATIy-6Y0LIA
>
Yikes. When a fuse blows, you replace it *once*. If it blows again, it
> Hi all,
>
> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
> main fuses (the 2A one on the rear panel). I opened the case and found
> two RIFA caps that had obviously blown, so replaced them, but it's
> still blowing fuses. I can't be 100% certain, but I'm pretty sure
> there's a fault with the PSU board as I get the briefest whiff of
> burning from that area each time I put a new fuse in and power up. The
> new fuse blows again before I get to see any smoke coming from
> anywhere at all. I'm linking to a diagram of the PSU as I'm not
> familiar with this circuit topology. If anyone can spot a component
> here that could have gone low-resistance and might be a good candidate
> for out-of-circuit testing, by all means let me know.
> Thanks,
>
> CD.
>
>
> https://disk.yandex.com/i/UhxATIy-6Y0LIA
>
ain't the fuse or a line transient.
Start with a DMM and check for shorted diodes in the input bridge and
then for a shorted filter cap at its output. (The schematic is more or
less completely illegible, or I'd give the ref des.)
Next most likely is a switch FET.
Cheers
Phil Hobbs
(proud owner of a 2467 that he almost never uses)
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
Cursitor Doom
Oct 25, 2022, 3:33:56 AM10/25/22
to
On Mon, 24 Oct 2022 20:38:01 -0400, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:
>Cursitor Doom wrote:
>> Hi all,
>>
>> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
>> main fuses (the 2A one on the rear panel). I opened the case and found
>> two RIFA caps that had obviously blown, so replaced them, but it's
>> still blowing fuses. I can't be 100% certain, but I'm pretty sure
>> there's a fault with the PSU board as I get the briefest whiff of
>> burning from that area each time I put a new fuse in and power up. The
>> new fuse blows again before I get to see any smoke coming from
>> anywhere at all. I'm linking to a diagram of the PSU as I'm not
>> familiar with this circuit topology. If anyone can spot a component
>> here that could have gone low-resistance and might be a good candidate
>> for out-of-circuit testing, by all means let me know.
>> Thanks,
>>
>> CD.
>>
>>
>> https://disk.yandex.com/i/UhxATIy-6Y0LIA
>>
>
>Yikes. When a fuse blows, you replace it *once*. If it blows again, it
>ain't the fuse or a line transient.
Yeah, well twice in this case. Replacing the RIFAs *usually* does the
<pcdhSpamM...@electrooptical.net> wrote:
>Cursitor Doom wrote:
>> Hi all,
>>
>> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing
>> main fuses (the 2A one on the rear panel). I opened the case and found
>> two RIFA caps that had obviously blown, so replaced them, but it's
>> still blowing fuses. I can't be 100% certain, but I'm pretty sure
>> there's a fault with the PSU board as I get the briefest whiff of
>> burning from that area each time I put a new fuse in and power up. The
>> new fuse blows again before I get to see any smoke coming from
>> anywhere at all. I'm linking to a diagram of the PSU as I'm not
>> familiar with this circuit topology. If anyone can spot a component
>> here that could have gone low-resistance and might be a good candidate
>> for out-of-circuit testing, by all means let me know.
>> Thanks,
>>
>> CD.
>>
>>
>> https://disk.yandex.com/i/UhxATIy-6Y0LIA
>>
>
>Yikes. When a fuse blows, you replace it *once*. If it blows again, it
>ain't the fuse or a line transient.
trick (I have to say, in a half-arsed defence of my appalling
conduct).
>
>Start with a DMM and check for shorted diodes in the input bridge and
>then for a shorted filter cap at its output. (The schematic is more or
>less completely illegible, or I'd give the ref des.)
that problem and have been able to see the part numbers okay.
>
>Next most likely is a switch FET.
Cursitor Doom
Oct 25, 2022, 3:34:39 AM10/25/22
to
On Mon, 24 Oct 2022 16:52:59 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:
>On Mon, 24 Oct 2022 22:17:57 +0100, Cursitor Doom <c...@notformail.com>
>wrote:
>
>>I'm no tech repairer; haven't got the necessary fine motor
>>skills, I'm afraid.
>
>Not a problem. Let a hand soldering robot do the precision work.
>Something like this soldering robot:
><https://www.promationusa.com/9101>
>More:
><https://www.promationusa.com/robotic-soldering-glance>
>and even more:
><https://www.google.com/search?q=hand+soldering+robot&tbm=isch>
Maybe one day I can get myself one of those, Jeff! :-D
wrote:
>On Mon, 24 Oct 2022 22:17:57 +0100, Cursitor Doom <c...@notformail.com>
>wrote:
>
>>I'm no tech repairer; haven't got the necessary fine motor
>>skills, I'm afraid.
>
>Not a problem. Let a hand soldering robot do the precision work.
>Something like this soldering robot:
><https://www.promationusa.com/9101>
>More:
><https://www.promationusa.com/robotic-soldering-glance>
>and even more:
><https://www.google.com/search?q=hand+soldering+robot&tbm=isch>
legg
Oct 25, 2022, 9:35:37 AM10/25/22
to
On Mon, 24 Oct 2022 10:35:23 -0700, Jeff Liebermann <je...@cruzio.com>
The video shows testing of two Y caps. These were originally
factory tested at 1500VAC/2700VDC, and have no reputation
for embarrassing field failures after 20+yrs.
X2 caps are desiged for 'impedance-limited' applications and
are tested at around 1KVAC/1500VDC.
Prior to single-board assembly mfring philosophy, these parts were
shipped with long leads, loose, in bulk containers, knocking heads
all the way. They were then subjected to short and long term lead
stress in manual lead dressing and final physical attachment.
Rifa was first to use that distinctive clear lacquer. I'm not sure
how many times that formula was 'improved', but parts would arrive
with visible cracks and would crumble around lead wires during
lead-forming.
That being said, there were sufficient 'incidents' in the first
20yrs of use to ensure that nobody in their right minds would
use them in new product, even in a list of alternates, in the
last 25 years.
TEK scopes that employ these parts are antiques, maintained by
enthusiasts, who will tell you all about the effects of heat,
humidity and just plain age on plastics, epoxies and other
components/materials used in them.
RL
factory tested at 1500VAC/2700VDC, and have no reputation
for embarrassing field failures after 20+yrs.
X2 caps are desiged for 'impedance-limited' applications and
are tested at around 1KVAC/1500VDC.
>
>>Metalized film parts are usually less dramatic in self-clearing
>>of internal faults, but in extreme cases, you still get thermal
>>runaway, as the faulting area expands and eats away at succesive
>>layers of the wrapped structure.
>
>I haven't bothered to perform a post mortem on a RIFA capacitor. I
>have several suitable microscopes and would expect to find holed in
>the dielectric (paper or plastic) and the metalization. The RIVA caps
>that failed have warped, cracked, melted, or crumbled outer plastic
>cases. For meaningful microscopy, I would need an old RIFA capacitor
>in an intact case.
>
Case degradation is a significant factor in aging of early production.
>>Metalized film parts are usually less dramatic in self-clearing
>>of internal faults, but in extreme cases, you still get thermal
>>runaway, as the faulting area expands and eats away at succesive
>>layers of the wrapped structure.
>
>I haven't bothered to perform a post mortem on a RIFA capacitor. I
>have several suitable microscopes and would expect to find holed in
>the dielectric (paper or plastic) and the metalization. The RIVA caps
>that failed have warped, cracked, melted, or crumbled outer plastic
>cases. For meaningful microscopy, I would need an old RIFA capacitor
>in an intact case.
>
Prior to single-board assembly mfring philosophy, these parts were
shipped with long leads, loose, in bulk containers, knocking heads
all the way. They were then subjected to short and long term lead
stress in manual lead dressing and final physical attachment.
Rifa was first to use that distinctive clear lacquer. I'm not sure
how many times that formula was 'improved', but parts would arrive
with visible cracks and would crumble around lead wires during
lead-forming.
That being said, there were sufficient 'incidents' in the first
20yrs of use to ensure that nobody in their right minds would
use them in new product, even in a list of alternates, in the
last 25 years.
TEK scopes that employ these parts are antiques, maintained by
enthusiasts, who will tell you all about the effects of heat,
humidity and just plain age on plastics, epoxies and other
components/materials used in them.
RL
legg
Oct 25, 2022, 9:52:13 AM10/25/22
to
On Mon, 24 Oct 2022 17:21:00 -0700 (PDT), Phil Allison
<palli...@gmail.com> wrote:
>legg wrote:
>------------------
>> >
>> >> Cursitor Doom wrote:
>> >>---------------------------------
>> >>> And if those
>> >>> caps fail open circuit (which they both did despite being X2 safety
>> >>> ones which are supposed to fail short)
>> >
>> >>** Really ? Where did you get that idea?
>> >>
>> >>Plenty are found open or with low values after long times in service.
>> >>X2 dropping caps used in smoke alarms regularly fail open.
>> >>
>> >>But those Rifa ones love to smoke and burn.
>> >>
>==================================================
>>
>> The smoking caps were metalized paper construction. These were good
>> enough in their day, with a demonstrated mtbf and safe self-healing,
>> while seals lasted. The outer sealing body tended to shrink and crack
>> with age, allowing ingress of air and moisture, compromising
>> performance. They are no longer made.
>
>** Rifa PME271 X2 caps are still made and widely available.
> Strangely they are also the most expensive X2 caps on offer for no good reason.
> Described as being of "metalised , impregnated paper " construction.
> Rifa also claim to be the only supplier .
Phil,
<palli...@gmail.com> wrote:
>legg wrote:
>------------------
>> >
>> >> Cursitor Doom wrote:
>> >>---------------------------------
>> >>> And if those
>> >>> caps fail open circuit (which they both did despite being X2 safety
>> >>> ones which are supposed to fail short)
>> >
>> >>** Really ? Where did you get that idea?
>> >>
>> >>Plenty are found open or with low values after long times in service.
>> >>X2 dropping caps used in smoke alarms regularly fail open.
>> >>
>> >>But those Rifa ones love to smoke and burn.
>> >>
>==================================================
>>
>> The smoking caps were metalized paper construction. These were good
>> enough in their day, with a demonstrated mtbf and safe self-healing,
>> while seals lasted. The outer sealing body tended to shrink and crack
>> with age, allowing ingress of air and moisture, compromising
>> performance. They are no longer made.
>
>** Rifa PME271 X2 caps are still made and widely available.
> Strangely they are also the most expensive X2 caps on offer for no good reason.
> Described as being of "metalised , impregnated paper " construction.
> Rifa also claim to be the only supplier .
You will not be able to purchase the 'exact' replacement, as the
series number no longer has the same operating voltage markings,
safety approval listing, pert numbering or material construction.
After all the merging and take-overs are done, it's unlikely
to be manufactured at the same physical plant, or using
similar equipment or materials, though safety docs used to be
pretty inflexible in that regard - one of the main trade effects
of VDE/IEC safety regime.
Costs reflect a low volume mfring environment due to buyer
reluctance to bother with 'improved' parts.
RL
Jeff Liebermann
Oct 25, 2022, 12:23:30 PM10/25/22
to
>(The schematic is more or
>less completely illegible, or I'd give the ref des.)
https://disk.yandex.com/i/UhxATIy-6Y0LIA
>less completely illegible, or I'd give the ref des.)
The Yandex viewer is blurry, even when viewed as "original size".
Try downloading the PNG file and viewing it with a better viewer at
100% magnification. The details are quite readable in Irfanview
(Windoze) and Nomacs (Linux). In Irfanview, the image can be
"Sharpened" by hitting "S" on the keyboard.
three_jeeps
Oct 25, 2022, 1:45:11 PM10/25/22
to
Cursitor Doom
Oct 25, 2022, 2:33:04 PM10/25/22
to
Here we go, gentlemen, the finished "repair" on the PSU board:
Before (the faulty RIFAs are arrowed since they're a bit hard to spot)
https://disk.yandex.com/i/9VID9SDCNLoxQw
After (the new replacements are not arrowed, since they're blindingly
obvious)
https://disk.yandex.com/i/uHJW9u33lWACVQ
It's just awful, isn't it?
Jeff Liebermann
Oct 25, 2022, 3:42:56 PM10/25/22
to
On Tue, 25 Oct 2022 19:33:00 +0100, Cursitor Doom <c...@notformail.com>
wrote:
I've done worse. I don't like the exposed hot wires, but since you're
the only person likely to be working on the scope, it's probably an
acceptable risk.
I suggest you tack the capacitors to the PCB with a little REMOVABLE
glue, such as hot melt glue or non-acetic-acid RTV.
wrote:
the only person likely to be working on the scope, it's probably an
acceptable risk.
I suggest you tack the capacitors to the PCB with a little REMOVABLE
glue, such as hot melt glue or non-acetic-acid RTV.
JC
Oct 25, 2022, 3:43:18 PM10/25/22
to
Tons of info out there on this power supply and how to fix:
https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/150/
Cursitor Doom
Oct 25, 2022, 4:38:55 PM10/25/22
to
On Tue, 25 Oct 2022 12:42:51 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:
>On Tue, 25 Oct 2022 19:33:00 +0100, Cursitor Doom <c...@notformail.com>
>wrote:
>
>>Here we go, gentlemen, the finished "repair" on the PSU board:
>>
>>Before (the faulty RIFAs are arrowed since they're a bit hard to spot)
>>https://disk.yandex.com/i/9VID9SDCNLoxQw
>>
>>After (the new replacements are not arrowed, since they're blindingly
>>obvious)
>>https://disk.yandex.com/i/uHJW9u33lWACVQ
>>
>>
>>It's just awful, isn't it?
>
>I've done worse. I don't like the exposed hot wires, but since you're
>the only person likely to be working on the scope, it's probably an
>acceptable risk.
Thanks, Jeff, I thought you'd tear me a new arsehole!
>I suggest you tack the capacitors to the PCB with a little REMOVABLE
>glue, such as hot melt glue or non-acetic-acid RTV.
In an ideal world and all that. Sadly, we both know that's not going
to happen, Jeff. :-(
wrote:
>On Tue, 25 Oct 2022 19:33:00 +0100, Cursitor Doom <c...@notformail.com>
>wrote:
>
>>Here we go, gentlemen, the finished "repair" on the PSU board:
>>
>>Before (the faulty RIFAs are arrowed since they're a bit hard to spot)
>>https://disk.yandex.com/i/9VID9SDCNLoxQw
>>
>>After (the new replacements are not arrowed, since they're blindingly
>>obvious)
>>https://disk.yandex.com/i/uHJW9u33lWACVQ
>>
>>
>>It's just awful, isn't it?
>
>I've done worse. I don't like the exposed hot wires, but since you're
>the only person likely to be working on the scope, it's probably an
>acceptable risk.
>I suggest you tack the capacitors to the PCB with a little REMOVABLE
>glue, such as hot melt glue or non-acetic-acid RTV.
to happen, Jeff. :-(
Cursitor Doom
Oct 25, 2022, 4:39:52 PM10/25/22
to
On Tue, 25 Oct 2022 15:43:14 -0400, JC <Chipbee4...@yahoo.com>
wrote:
>Cursitor Doom wrote:
>>
>> Here we go, gentlemen, the finished "repair" on the PSU board:
>>
>> Before (the faulty RIFAs are arrowed since they're a bit hard to spot)
>> https://disk.yandex.com/i/9VID9SDCNLoxQw
>>
>> After (the new replacements are not arrowed, since they're blindingly
>> obvious)
>> https://disk.yandex.com/i/uHJW9u33lWACVQ
>>
>>
>> It's just awful, isn't it?
>>
>Probably won't fit back in the scope cos of the IEC filter.
It does actually fit back in again - *just* about.
>Tons of info out there on this power supply and how to fix:
>
>https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/150/
Many thanks for that indeed.
wrote:
>Cursitor Doom wrote:
>>
>> Here we go, gentlemen, the finished "repair" on the PSU board:
>>
>> Before (the faulty RIFAs are arrowed since they're a bit hard to spot)
>> https://disk.yandex.com/i/9VID9SDCNLoxQw
>>
>> After (the new replacements are not arrowed, since they're blindingly
>> obvious)
>> https://disk.yandex.com/i/uHJW9u33lWACVQ
>>
>>
>> It's just awful, isn't it?
>>
>Probably won't fit back in the scope cos of the IEC filter.
>Tons of info out there on this power supply and how to fix:
>
>https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/150/
Cursitor Doom
Oct 25, 2022, 4:54:48 PM10/25/22
to
On Tue, 25 Oct 2022 09:36:35 -0400, legg <le...@nospam.magma.ca> wrote:
>The video shows testing of two Y caps. These were originally
>factory tested at 1500VAC/2700VDC, and have no reputation
>for embarrassing field failures after 20+yrs.
>
>X2 caps are desiged for 'impedance-limited' applications and
>are tested at around 1KVAC/1500VDC.
Do you know why these caps usually have their self-resonant frequency
>The video shows testing of two Y caps. These were originally
>factory tested at 1500VAC/2700VDC, and have no reputation
>for embarrassing field failures after 20+yrs.
>
>X2 caps are desiged for 'impedance-limited' applications and
>are tested at around 1KVAC/1500VDC.
marked on the side of them? That's always puzzled me.
three_jeeps
Oct 25, 2022, 5:19:41 PM10/25/22
to
On Saturday, October 22, 2022 at 2:34:59 PM UTC-4, Cursitor Doom wrote:
> On Sat, 22 Oct 2022 08:08:25 -0700 (PDT), "Peter W."
> <peterw...@gmail.com> wrote:
>
> >Did the caps fail Open or Short?
> >
> >Peter Wieck
> >Melrose Park, P
> These are X2 caps and supposed to fail short. However, for whatever
> reason, they both failed open.
Fail short...really? Why would you want a cap that is across the supply line to fail short? Just to make sure the fuse blows?
It is my understanding that X and Y capacitors experience line spikes, and will endure multiple small breakdowns over the years as a result of this stress. They fail open because local heating caused by a microscopic dielectric breakdown results in polypropylene melting, which seals off the "edge" of the breakdown.
Is this not correct??
> On Sat, 22 Oct 2022 08:08:25 -0700 (PDT), "Peter W."
> <peterw...@gmail.com> wrote:
>
> >Did the caps fail Open or Short?
> >
> >Peter Wieck
> >Melrose Park, P
> These are X2 caps and supposed to fail short. However, for whatever
> reason, they both failed open.
Fail short...really? Why would you want a cap that is across the supply line to fail short? Just to make sure the fuse blows?
It is my understanding that X and Y capacitors experience line spikes, and will endure multiple small breakdowns over the years as a result of this stress. They fail open because local heating caused by a microscopic dielectric breakdown results in polypropylene melting, which seals off the "edge" of the breakdown.
Is this not correct??
Cursitor Doom
Oct 25, 2022, 5:38:32 PM10/25/22
to
my orginal remark, I did say they are *supposed* to fail short, which
makes pretty clear that was the intention of the manufacturer even if
they were not successful in many instances.
Rayner Lucas
Oct 25, 2022, 8:04:12 PM10/25/22
to
In article <4696384c-8b39-4bae...@googlegroups.com>,
palli...@gmail.com says...
that I'm sure can't possibly have been good ones. All of them have
developed a couple of small cracks in the casing, just from sitting
unused in a parts box.
So if anyone was wondering if they'd fixed the defects in the design at
any point in the last 40+ years, apparently not.
> IME Rifa X2s are notorious for catching fire and filling the room with
> acrid smoke. Happened twice, right in front of me, first case was a
> room heater and the second with a portable TV.
Yep, they're a menace all right. These days I pre-emptively check any
mains-powered electronics from the 80s and 90s for them, which
thankfully meant I got them out of my Tek 2445A before they popped. Wish
I'd been more alert with the 2235A; I spent ages cleaning sticky brown
crud out of the crevices of that one.
And then there was the HP spectrum analyser where I thought I'd saved
myself a heap of trouble by extracting all eight(!) Rifa capacitors from
its power supply. Plugged it in, and half an hour later a thick cloud of
truly foul phenolic smoke poured out. Opened it up to find that it had
blown part of the case off its power inlet. Turns out that Schaffner
filtered power inlets can *also* contain Rifa (or very similar) caps,
concealed inside a metal casing and potting compound just to add extra
force and noxious smells to the eventual and inevitable explosion.
I'm pretty sure anyone who works on older electronics eventually
develops their very own rant about these accursed objects.
Rayner
palli...@gmail.com says...
>
> ** Rifa PME271 X2 caps are still made and widely available.
> Strangely they are also the most expensive X2 caps on offer for no
> good reason.
I got a handful of brand new PME271 Y caps a few years ago, for reasons
> ** Rifa PME271 X2 caps are still made and widely available.
> Strangely they are also the most expensive X2 caps on offer for no
> good reason.
that I'm sure can't possibly have been good ones. All of them have
developed a couple of small cracks in the casing, just from sitting
unused in a parts box.
So if anyone was wondering if they'd fixed the defects in the design at
any point in the last 40+ years, apparently not.
> IME Rifa X2s are notorious for catching fire and filling the room with
> acrid smoke. Happened twice, right in front of me, first case was a
> room heater and the second with a portable TV.
mains-powered electronics from the 80s and 90s for them, which
thankfully meant I got them out of my Tek 2445A before they popped. Wish
I'd been more alert with the 2235A; I spent ages cleaning sticky brown
crud out of the crevices of that one.
And then there was the HP spectrum analyser where I thought I'd saved
myself a heap of trouble by extracting all eight(!) Rifa capacitors from
its power supply. Plugged it in, and half an hour later a thick cloud of
truly foul phenolic smoke poured out. Opened it up to find that it had
blown part of the case off its power inlet. Turns out that Schaffner
filtered power inlets can *also* contain Rifa (or very similar) caps,
concealed inside a metal casing and potting compound just to add extra
force and noxious smells to the eventual and inevitable explosion.
I'm pretty sure anyone who works on older electronics eventually
develops their very own rant about these accursed objects.
Rayner
legg
Oct 26, 2022, 8:33:08 AM10/26/22
to
My guess is you just prefered to solder from the comp
side.
RL
Cursitor Doom
Oct 26, 2022, 11:15:06 AM10/26/22
to
suspect" and there might be fewer than half a dozen to do, the
prospect still fills me with horror. If they only knew how ironic the
"Just" bit strikes me in suggestions like that.
Peter W.
Oct 26, 2022, 11:57:09 AM10/26/22
to
> It's really not my thing. When people say, "Just recap anything
> suspect" and there might be fewer than half a dozen to do, the
> prospect still fills me with horror. If they only knew how ironic the
> "Just" bit strikes me in suggestions like that.
The problem with vintage equipment, however well designed and well built, is that parts within it age. Typically, items that are approaching, or exceeding 30 years old will have some marginal parts within. Further, if those parts are 'common' as in "many of them", if one fails the others will not be far behind. Some truisms:
> suspect" and there might be fewer than half a dozen to do, the
> prospect still fills me with horror. If they only knew how ironic the
> "Just" bit strikes me in suggestions like that.
a) As in the Holland America commercials - Time is a precious commodity.
b) Most (not all) hobbyists are not limited by cost constraints for a few parts. So, a US$20-or-equivalent investment to save a valuable item is not outrageous.
c) Most of the effort in repairs is 'getting to it' - the taking-apart, the testing, documenting, and then reassembly.
d) The actual repairs take very little time.
So, when whatever the device might be, when it is taken apart, *THEN* is the time to refurbish the entirety to the greatest extent possible - to avoid having to repeat the process if nothing else. Analogy: the engine in your vehicle spins one (1) bearing. You would replace _ALL_ of the bearings, as the incremental cost of the additional bearings against the cost of the tear-down is tiny, and the rewards significant. There is a school of thought that suggests that repairs are made only to the minimum necessary. Subscribers to this theory are the ones that one sees stranded on the side of the road in a blinding snowstorm.
Your power-supply went through a traumatic event - and it is supplying a complex and expensive piece of equipment. Consider it in that light.
As to soldering and technique - time and repetition will give you more confidence.
Peter W.
Oct 26, 2022, 11:57:59 AM10/26/22
to
That would be Viking....
Cursitor Doom
Oct 26, 2022, 5:18:49 PM10/26/22
to
On Wed, 26 Oct 2022 08:57:06 -0700 (PDT), "Peter W."
<peterw...@gmail.com> wrote:
>> It's really not my thing. When people say, "Just recap anything
>> suspect" and there might be fewer than half a dozen to do, the
>> prospect still fills me with horror. If they only knew how ironic the
>> "Just" bit strikes me in suggestions like that.
>
>The problem with vintage equipment, however well designed and well built, is that parts within it age. Typically, items that are approaching, or exceeding 30 years old will have some marginal parts within. Further, if those parts are 'common' as in "many of them", if one fails the others will not be far behind. Some truisms:
>
>a) As in the Holland America commercials - Time is a precious commodity.
>b) Most (not all) hobbyists are not limited by cost constraints for a few parts. So, a US$20-or-equivalent investment to save a valuable item is not outrageous.
>c) Most of the effort in repairs is 'getting to it' - the taking-apart, the testing, documenting, and then reassembly.
>d) The actual repairs take very little time.
"The actual repairs take very little time."
If you only knew the irony of that statement when the task is
<peterw...@gmail.com> wrote:
>> It's really not my thing. When people say, "Just recap anything
>> suspect" and there might be fewer than half a dozen to do, the
>> prospect still fills me with horror. If they only knew how ironic the
>> "Just" bit strikes me in suggestions like that.
>
>The problem with vintage equipment, however well designed and well built, is that parts within it age. Typically, items that are approaching, or exceeding 30 years old will have some marginal parts within. Further, if those parts are 'common' as in "many of them", if one fails the others will not be far behind. Some truisms:
>
>a) As in the Holland America commercials - Time is a precious commodity.
>b) Most (not all) hobbyists are not limited by cost constraints for a few parts. So, a US$20-or-equivalent investment to save a valuable item is not outrageous.
>c) Most of the effort in repairs is 'getting to it' - the taking-apart, the testing, documenting, and then reassembly.
>d) The actual repairs take very little time.
"The actual repairs take very little time."
completeed by someone with my eyesight and fine motor skills.
>As to soldering and technique - time and repetition will give you more confidence.
every bit as shit at it as I was half a century ago. I have not
improved one iota and only a damn fool would believe the future's
going to be any better than the past with a skill set like mine.
Tony Stewart
Nov 1, 2022, 1:47:04 AM11/1/22
to
The key to faster resolution of fusing faults is test method for fault
isolation.
Possible methods include:
1. Input voltage attenuation below fault threshold and probe test points.
2. isolate secondary sections by disconnect
3. Check for thermal hotspots safely.
isolation.
Possible methods include:
1. Input voltage attenuation below fault threshold and probe test points.
2. isolate secondary sections by disconnect
3. Check for thermal hotspots safely.
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