Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
Old 'Scope inductor and cap help please
110 views
Skip to first unread message
et...@whidbey.com
Oct 4, 2019, 1:47:56 PM10/4/19
to
Down with water heaters and up with old tube oscilloscopes, that's
what I say.
Well, I picked up a couple of old scopes. One is a Dumont 241 and
the other is a DeVRY. No model number on the DeVRY. It's not a Bell
and Howell model 34, but it is similar, and older. As near as I can
tell it is also a B&H, but I can't tell much. It came with
construction manual as it was a kit. The manual is # 9027A. It has
some sections of the schematic for the scope but not the whole
schematic.
Though the scope sorta works it ignores all signals fed into it. I
can get a dot, a line, and a small waveform but those just come from
switching the dials. By small I mean it is not very tall or long on
the CRT. It is not a pure sine wave but instead looks like a jagged
triangle wave. Sort of.
On the front of the manual someone wrote that an inductor is bad.
It is a 35uH coil wound on a 10 meg resistor. It is called a peaking
coil and is in the signal path of the vertical amplifier.
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?
I also would like some advice on where to buy caps for tube gear.
Digikey or Mouser? Someplace better?
Finally, it looks like I need to get me a cap tester. One that can
check caps in circuit would be ideal. But since this is a hobby I need
to keep the costs down. So suggestions would be great.
Thanks for reading.
Cheers,
Eric
what I say.
Well, I picked up a couple of old scopes. One is a Dumont 241 and
the other is a DeVRY. No model number on the DeVRY. It's not a Bell
and Howell model 34, but it is similar, and older. As near as I can
tell it is also a B&H, but I can't tell much. It came with
construction manual as it was a kit. The manual is # 9027A. It has
some sections of the schematic for the scope but not the whole
schematic.
Though the scope sorta works it ignores all signals fed into it. I
can get a dot, a line, and a small waveform but those just come from
switching the dials. By small I mean it is not very tall or long on
the CRT. It is not a pure sine wave but instead looks like a jagged
triangle wave. Sort of.
On the front of the manual someone wrote that an inductor is bad.
It is a 35uH coil wound on a 10 meg resistor. It is called a peaking
coil and is in the signal path of the vertical amplifier.
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?
I also would like some advice on where to buy caps for tube gear.
Digikey or Mouser? Someplace better?
Finally, it looks like I need to get me a cap tester. One that can
check caps in circuit would be ideal. But since this is a hobby I need
to keep the costs down. So suggestions would be great.
Thanks for reading.
Cheers,
Eric
Fox's Mercantile
Oct 4, 2019, 3:04:44 PM10/4/19
to
On 10/4/19 12:53 PM, et...@whidbey.com wrote:
> I have not been able to find this style of inductor online. Maybe
> I'm not using the correct search terms. Can anyone point me in the
> correct direction? Maybe I could just wind my own. Anybody know what
> the permeability of a carbon comp resistor is?
The permeability is zero. It's "just a coil form"
> I have not been able to find this style of inductor online. Maybe
> I'm not using the correct search terms. Can anyone point me in the
> correct direction? Maybe I could just wind my own. Anybody know what
> the permeability of a carbon comp resistor is?
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.
--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
peterw...@gmail.com
Oct 4, 2019, 3:11:34 PM10/4/19
to
A few things:
a) I keep the Peak/Atlas ESR & Cap tester. There are much cheaper Chinese devices that test more things than it does, but for reliability and simplicity, I find it a better choice. Note that if all you want is capacity, any decent DVM/VOM will have that function these days. But having reliable ESR readings is very helpful.
b) I also keep a fairly vintage (maybe 20 years old) B&K LCR Meter, useful for measuring inductors. I see them on-line in the $$$ range, with Chinese LCR meters along side in the $$ range. I got mine from a retired Tech at a garage sale. Recently calibrated (then) and works fine.
c) Mouser and DigiKey are my first two choices, with Newark (Element 14) being next. Note that Mouser will answer the phone, typically by/with a knowledgeable person, typically also patient with amateurs.
d) LR networks are common enough and there is nothing magical about them. Winding one yourself is no trick either. The trick is to wind on a few more turns, then back off until it is where you want it to be. In the factory, that would not have been necessary, but with such an old device, pretty much nothing is as it was then, so you may need a bit of range. Nor does that coil have to be around the resistor if space permits. But, if you are lucky enough to be able to find a 10-meg film resistor of the correct diameter and wire of the correct gauge, just count the turns and rewind.
Not knowing where you are, I would suggest you look for vintage radio clubs and/or hamfests in your region. Oftentimes, you can find parts, pieces and all sorts of vintage stuff at such events, and advice through clubs that is far more practical and immediate than much offered here. I make it to Kutztown twice a year, which serves very nearly all of my needs.
Peter Wieck
Melrose Park, PA
a) I keep the Peak/Atlas ESR & Cap tester. There are much cheaper Chinese devices that test more things than it does, but for reliability and simplicity, I find it a better choice. Note that if all you want is capacity, any decent DVM/VOM will have that function these days. But having reliable ESR readings is very helpful.
b) I also keep a fairly vintage (maybe 20 years old) B&K LCR Meter, useful for measuring inductors. I see them on-line in the $$$ range, with Chinese LCR meters along side in the $$ range. I got mine from a retired Tech at a garage sale. Recently calibrated (then) and works fine.
c) Mouser and DigiKey are my first two choices, with Newark (Element 14) being next. Note that Mouser will answer the phone, typically by/with a knowledgeable person, typically also patient with amateurs.
d) LR networks are common enough and there is nothing magical about them. Winding one yourself is no trick either. The trick is to wind on a few more turns, then back off until it is where you want it to be. In the factory, that would not have been necessary, but with such an old device, pretty much nothing is as it was then, so you may need a bit of range. Nor does that coil have to be around the resistor if space permits. But, if you are lucky enough to be able to find a 10-meg film resistor of the correct diameter and wire of the correct gauge, just count the turns and rewind.
Not knowing where you are, I would suggest you look for vintage radio clubs and/or hamfests in your region. Oftentimes, you can find parts, pieces and all sorts of vintage stuff at such events, and advice through clubs that is far more practical and immediate than much offered here. I make it to Kutztown twice a year, which serves very nearly all of my needs.
Peter Wieck
Melrose Park, PA
Ralph Mowery
Oct 4, 2019, 6:03:15 PM10/4/19
to
In article <wOidnSPBTuJZCgrA...@giganews.com>,
jda...@att.net says...
I do agree that resistors that have over 100 times the resistance
(reactance) of the wire will appear to almost not be there and just a
coil form.
jda...@att.net says...
> I have not been able to find this style of inductor online. Maybe
> > I'm not using the correct search terms. Can anyone point me in the
> > correct direction? Maybe I could just wind my own. Anybody know what
> > the permeability of a carbon comp resistor is?
>
> The permeability is zero. It's "just a coil form"
> Unwind the old one, count the number of turns, measure the wire
> size. Wind new turns and replace.
>
> --
>
>
Would it not be 1 instead of zero ? The same as air.
> > I'm not using the correct search terms. Can anyone point me in the
> > correct direction? Maybe I could just wind my own. Anybody know what
> > the permeability of a carbon comp resistor is?
>
> The permeability is zero. It's "just a coil form"
> Unwind the old one, count the number of turns, measure the wire
> size. Wind new turns and replace.
>
> --
>
>
I do agree that resistors that have over 100 times the resistance
(reactance) of the wire will appear to almost not be there and just a
coil form.
Fox's Mercantile
Oct 4, 2019, 6:29:39 PM10/4/19
to
On 10/4/19 5:03 PM, Ralph Mowery wrote:
> jda...@att.net says...
>> I have not been able to find this style of inductor online. Maybe
>>> I'm not using the correct search terms. Can anyone point me in the
>>> correct direction? Maybe I could just wind my own. Anybody know what
>>> the permeability of a carbon comp resistor is?
>> The permeability is zero. It's "just a coil form"
>> Unwind the old one, count the number of turns, measure the wire
>> size. Wind new turns and replace.
>>
>> --
>>
>>
> Would it not be 1 instead of zero ? The same as air.
You're right. It's 1.
> jda...@att.net says...
>> I have not been able to find this style of inductor online. Maybe
>>> I'm not using the correct search terms. Can anyone point me in the
>>> correct direction? Maybe I could just wind my own. Anybody know what
>>> the permeability of a carbon comp resistor is?
>> The permeability is zero. It's "just a coil form"
>> Unwind the old one, count the number of turns, measure the wire
>> size. Wind new turns and replace.
>>
>> --
>>
>>
> Would it not be 1 instead of zero ? The same as air.
et...@whidbey.com
Oct 4, 2019, 7:07:39 PM10/4/19
to
On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jda...@att.net>
wrote:
>On 10/4/19 12:53 PM, et...@whidbey.com wrote:
>> I have not been able to find this style of inductor online. Maybe
>> I'm not using the correct search terms. Can anyone point me in the
>> correct direction? Maybe I could just wind my own. Anybody know what
>> the permeability of a carbon comp resistor is?
>
>The permeability is zero. It's "just a coil form"
>Unwind the old one, count the number of turns, measure the wire
>size. Wind new turns and replace.
The schematic just shows the inductor in the circuit. It does not show
the inductor as being in parallel with a resistor. And it is described
as 35 uH "ON 10 M". So I'm thinking I either can just replace the
inductor with an off the shelf 35 uH coil and not worry about the
resistor or connect the coil and a 10 meg resistor in parallel.
Eric
wrote:
>On 10/4/19 12:53 PM, et...@whidbey.com wrote:
>> I have not been able to find this style of inductor online. Maybe
>> I'm not using the correct search terms. Can anyone point me in the
>> correct direction? Maybe I could just wind my own. Anybody know what
>> the permeability of a carbon comp resistor is?
>
>The permeability is zero. It's "just a coil form"
>Unwind the old one, count the number of turns, measure the wire
>size. Wind new turns and replace.
the inductor as being in parallel with a resistor. And it is described
as 35 uH "ON 10 M". So I'm thinking I either can just replace the
inductor with an off the shelf 35 uH coil and not worry about the
resistor or connect the coil and a 10 meg resistor in parallel.
Eric
Fox's Mercantile
Oct 4, 2019, 7:31:47 PM10/4/19
to
On 10/4/19 6:13 PM, et...@whidbey.com wrote:
> On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jda...@att.net>
> wrote:
>
>> On 10/4/19 12:53 PM, et...@whidbey.com wrote:
>>> I have not been able to find this style of inductor online. Maybe
>>> I'm not using the correct search terms. Can anyone point me in the
>>> correct direction? Maybe I could just wind my own. Anybody know what
>>> the permeability of a carbon comp resistor is?
>>
>> The permeability is zero.
Correction, it's 1.
> On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jda...@att.net>
> wrote:
>
>> On 10/4/19 12:53 PM, et...@whidbey.com wrote:
>>> I have not been able to find this style of inductor online. Maybe
>>> I'm not using the correct search terms. Can anyone point me in the
>>> correct direction? Maybe I could just wind my own. Anybody know what
>>> the permeability of a carbon comp resistor is?
>>
>> The permeability is zero.
It's "just a coil form"
>> Unwind the old one, count the number of turns, measure the wire
>> size. Wind new turns and replace.
> The schematic just shows the inductor in the circuit. It does not show
> the inductor as being in parallel with a resistor. And it is described
> as 35 uH "ON 10 M". So I'm thinking I either can just replace the
> inductor with an off the shelf 35 uH coil and not worry about the
> resistor or connect the coil and a 10 meg resistor in parallel.
> Eric
>
You don't need the 10 meg ohm resistor.
>> Unwind the old one, count the number of turns, measure the wire
>> size. Wind new turns and replace.
> The schematic just shows the inductor in the circuit. It does not show
> the inductor as being in parallel with a resistor. And it is described
> as 35 uH "ON 10 M". So I'm thinking I either can just replace the
> inductor with an off the shelf 35 uH coil and not worry about the
> resistor or connect the coil and a 10 meg resistor in parallel.
> Eric
>
This will be fine.
<https://www.mouser.com/ProductDetail/API-Delevan/1025-56J?qs=sGAEpiMZZMsg%252By3WlYCkU%2Fuy0w9T3GDQ2AQE7IS6yJE%3D>
tabb...@gmail.com
Oct 4, 2019, 7:54:01 PM10/4/19
to
NT
legg
Oct 5, 2019, 9:36:24 AM10/5/19
to
On Fri, 4 Oct 2019 17:29:31 -0500, Fox's Mercantile <jda...@att.net>
wrote:
>On 10/4/19 5:03 PM, Ralph Mowery wrote:
>> jda...@att.net says...
>>> I have not been able to find this style of inductor online. Maybe
>>>> I'm not using the correct search terms. Can anyone point me in the
>>>> correct direction? Maybe I could just wind my own. Anybody know what
>>>> the permeability of a carbon comp resistor is?
>>> The permeability is zero. It's "just a coil form"
>>> Unwind the old one, count the number of turns, measure the wire
>>> size. Wind new turns and replace.
>>>
>>> --
>>>
>>>
>> Would it not be 1 instead of zero ? The same as air.
>
>You're right. It's 1.
Permeability of free space is 4 x pi x 10^-7.
... but yeah, it's just a coil former.
RL
wrote:
>On 10/4/19 5:03 PM, Ralph Mowery wrote:
>> jda...@att.net says...
>>> I have not been able to find this style of inductor online. Maybe
>>>> I'm not using the correct search terms. Can anyone point me in the
>>>> correct direction? Maybe I could just wind my own. Anybody know what
>>>> the permeability of a carbon comp resistor is?
>>> The permeability is zero. It's "just a coil form"
>>> Unwind the old one, count the number of turns, measure the wire
>>> size. Wind new turns and replace.
>>>
>>> --
>>>
>>>
>> Would it not be 1 instead of zero ? The same as air.
>
>You're right. It's 1.
... but yeah, it's just a coil former.
RL
et...@whidbey.com
Oct 5, 2019, 12:58:14 PM10/5/19
to
On Fri, 4 Oct 2019 18:31:38 -0500, Fox's Mercantile <jda...@att.net>
to see this old scope work.
Eric
wrote:
>On 10/4/19 6:13 PM, et...@whidbey.com wrote:
>> On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jda...@att.net>
>> wrote:
>>
>>> On 10/4/19 12:53 PM, et...@whidbey.com wrote:
>>>> I have not been able to find this style of inductor online. Maybe
>>>> I'm not using the correct search terms. Can anyone point me in the
>>>> correct direction? Maybe I could just wind my own. Anybody know what
>>>> the permeability of a carbon comp resistor is?
>>>
>>> The permeability is zero.
>Correction, it's 1.
>It's "just a coil form"
>>> Unwind the old one, count the number of turns, measure the wire
>>> size. Wind new turns and replace.
>> The schematic just shows the inductor in the circuit. It does not show
>> the inductor as being in parallel with a resistor. And it is described
>> as 35 uH "ON 10 M". So I'm thinking I either can just replace the
>> inductor with an off the shelf 35 uH coil and not worry about the
>> resistor or connect the coil and a 10 meg resistor in parallel.
>> Eric
>>
>
>You don't need the 10 meg ohm resistor.
>This will be fine.
><https://www.mouser.com/ProductDetail/API-Delevan/1025-56J?qs=sGAEpiMZZMsg%252By3WlYCkU%2Fuy0w9T3GDQ2AQE7IS6yJE%3D>
Thanks, I thought so. Today I order caps and an inductor. I'm excited
>On 10/4/19 6:13 PM, et...@whidbey.com wrote:
>> On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jda...@att.net>
>> wrote:
>>
>>> On 10/4/19 12:53 PM, et...@whidbey.com wrote:
>>>> I have not been able to find this style of inductor online. Maybe
>>>> I'm not using the correct search terms. Can anyone point me in the
>>>> correct direction? Maybe I could just wind my own. Anybody know what
>>>> the permeability of a carbon comp resistor is?
>>>
>>> The permeability is zero.
>Correction, it's 1.
>It's "just a coil form"
>>> Unwind the old one, count the number of turns, measure the wire
>>> size. Wind new turns and replace.
>> The schematic just shows the inductor in the circuit. It does not show
>> the inductor as being in parallel with a resistor. And it is described
>> as 35 uH "ON 10 M". So I'm thinking I either can just replace the
>> inductor with an off the shelf 35 uH coil and not worry about the
>> resistor or connect the coil and a 10 meg resistor in parallel.
>> Eric
>>
>
>You don't need the 10 meg ohm resistor.
>This will be fine.
><https://www.mouser.com/ProductDetail/API-Delevan/1025-56J?qs=sGAEpiMZZMsg%252By3WlYCkU%2Fuy0w9T3GDQ2AQE7IS6yJE%3D>
to see this old scope work.
Eric
three_jeeps
Oct 6, 2019, 9:11:02 PM10/6/19
to
Given the age of the scope, you might want to consider replacing the electrolytic in the power supply section. Everything starts with solid, clean and correct power
J
J
et...@whidbey.com
Oct 7, 2019, 11:42:18 AM10/7/19
to
electrolytics there are some others that, from what I've read about
and seen on YouTube, are also suspect.
Eric
Fox's Mercantile
Oct 7, 2019, 1:03:22 PM10/7/19
to
On 10/7/19 10:48 AM, et...@whidbey.com wrote:
> I will be replacing practically every cap. Besides all the
Replace ALL the electrolytics.
Replace ALL the paper caps.
Leave the silver dipped micas, tubular ceramics, and any "postage
stamp" micas alone for the time being.
Replace them one at a time. Take pictures, make notes.
> I will be replacing practically every cap. Besides all the
> electrolytics there are some others that, from what I've read about
> and seen on YouTube, are also suspect.
> Eric
Caps are cheap. Collateral damages from bad caps are not cheap.
> and seen on YouTube, are also suspect.
> Eric
Replace ALL the electrolytics.
Replace ALL the paper caps.
Leave the silver dipped micas, tubular ceramics, and any "postage
stamp" micas alone for the time being.
Replace them one at a time. Take pictures, make notes.
et...@whidbey.com
Oct 8, 2019, 2:12:57 PM10/8/19
to
On Mon, 7 Oct 2019 12:03:13 -0500, Fox's Mercantile <jda...@att.net>
wrote:
>On 10/7/19 10:48 AM, et...@whidbey.com wrote:
>> I will be replacing practically every cap. Besides all the
>> electrolytics there are some others that, from what I've read about
>> and seen on YouTube, are also suspect.
>> Eric
>
>Caps are cheap. Collateral damages from bad caps are not cheap.
>Replace ALL the electrolytics.
>Replace ALL the paper caps.
>
>Leave the silver dipped micas, tubular ceramics, and any "postage
>stamp" micas alone for the time being.
>
>Replace them one at a time. Take pictures, make notes.
I have tried to identify what types of caps are in this scope but
have been unable to find a site that shows the caps I'm wondering
about. I think some are tubular ceramic caps because they are white
ceramic tubes that are filled with some sort of hard potting compound.
The other type of cap is also tubular but is molded brown hard
plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
at 400 WVDC. Anybody know?
Thanks,
Eric
wrote:
>On 10/7/19 10:48 AM, et...@whidbey.com wrote:
>> I will be replacing practically every cap. Besides all the
>> electrolytics there are some others that, from what I've read about
>> and seen on YouTube, are also suspect.
>> Eric
>
>Caps are cheap. Collateral damages from bad caps are not cheap.
>Replace ALL the electrolytics.
>Replace ALL the paper caps.
>
>Leave the silver dipped micas, tubular ceramics, and any "postage
>stamp" micas alone for the time being.
>
>Replace them one at a time. Take pictures, make notes.
have been unable to find a site that shows the caps I'm wondering
about. I think some are tubular ceramic caps because they are white
ceramic tubes that are filled with some sort of hard potting compound.
The other type of cap is also tubular but is molded brown hard
plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
at 400 WVDC. Anybody know?
Thanks,
Eric
Fox's Mercantile
Oct 8, 2019, 2:57:00 PM10/8/19
to
On 10/8/19 1:19 PM, et...@whidbey.com wrote:
> I have tried to identify what types of caps are in this scope but
> have been unable to find a site that shows the caps I'm wondering
> about. I think some are tubular ceramic caps because they are white
> ceramic tubes that are filled with some sort of hard potting compound.
> The other type of cap is also tubular but is molded brown hard
> plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
> at 400 WVDC. Anybody know?
The wax paper caps come in several varieties.
> I have tried to identify what types of caps are in this scope but
> have been unable to find a site that shows the caps I'm wondering
> about. I think some are tubular ceramic caps because they are white
> ceramic tubes that are filled with some sort of hard potting compound.
> The other type of cap is also tubular but is molded brown hard
> plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
> at 400 WVDC. Anybody know?
(Usually) Brown cardboard with a wax coating.
Molded plastic, and ceramic tube.
All of those need to be replaced.
et...@whidbey.com
Oct 8, 2019, 4:50:20 PM10/8/19
to
On Tue, 8 Oct 2019 13:56:52 -0500, Fox's Mercantile <jda...@att.net>
wrote:
>On 10/8/19 1:19 PM, et...@whidbey.com wrote:
>> I have tried to identify what types of caps are in this scope but
>> have been unable to find a site that shows the caps I'm wondering
>> about. I think some are tubular ceramic caps because they are white
>> ceramic tubes that are filled with some sort of hard potting compound.
>> The other type of cap is also tubular but is molded brown hard
>> plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
>> at 400 WVDC. Anybody know?
>
>The wax paper caps come in several varieties.
>(Usually) Brown cardboard with a wax coating.
>Molded plastic, and ceramic tube.
>All of those need to be replaced.
What kind of cap should I replace them with?
Thanks,
Eric
wrote:
>On 10/8/19 1:19 PM, et...@whidbey.com wrote:
>> I have tried to identify what types of caps are in this scope but
>> have been unable to find a site that shows the caps I'm wondering
>> about. I think some are tubular ceramic caps because they are white
>> ceramic tubes that are filled with some sort of hard potting compound.
>> The other type of cap is also tubular but is molded brown hard
>> plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
>> at 400 WVDC. Anybody know?
>
>The wax paper caps come in several varieties.
>(Usually) Brown cardboard with a wax coating.
>Molded plastic, and ceramic tube.
>All of those need to be replaced.
Thanks,
Eric
Fox's Mercantile
Oct 8, 2019, 5:03:54 PM10/8/19
to
et...@whidbey.com
Oct 9, 2019, 11:42:07 AM10/9/19
to
On Tue, 8 Oct 2019 16:03:45 -0500, Fox's Mercantile <jda...@att.net>
wrote:
>On 10/8/19 3:56 PM, et...@whidbey.com wrote:
>> What kind of cap should I replace them with?
>
>These:
><http://www.tuberadios.com/capacitors/>
>Yellow mylar film 630 vdc.
Thanks. I'm ordering all the caps right now on my tablet. With the
little inductor its way I''l be set to repair the scope. BTW, as I was
looking for all the caps I found a broken wire in the vertical stage.
After figuring out where it was supposed to go and re-soldering it I
tried the scope again and now it works! Still, the waveform is messed
up so the new caps are needed.
Eric
wrote:
>On 10/8/19 3:56 PM, et...@whidbey.com wrote:
>> What kind of cap should I replace them with?
>
>These:
><http://www.tuberadios.com/capacitors/>
>Yellow mylar film 630 vdc.
little inductor its way I''l be set to repair the scope. BTW, as I was
looking for all the caps I found a broken wire in the vertical stage.
After figuring out where it was supposed to go and re-soldering it I
tried the scope again and now it works! Still, the waveform is messed
up so the new caps are needed.
Eric
tabb...@gmail.com
Oct 9, 2019, 11:53:33 AM10/9/19
to
On Monday, 7 October 2019 18:03:22 UTC+1, Fox's Mercantile wrote:
> On 10/7/19 10:48 AM, et...@whidbey.com wrote:
> > I will be replacing practically every cap. Besides all the
> > electrolytics there are some others that, from what I've read about
> > and seen on YouTube, are also suspect.
> > Eric
>
> Caps are cheap. Collateral damages from bad caps are not cheap.
> Replace ALL the electrolytics.
> Replace ALL the paper caps.
>
> Leave the silver dipped micas, tubular ceramics, and any "postage
> stamp" micas alone for the time being.
>
> Replace them one at a time. Take pictures, make notes.
You will of course encounter restorers who don't agree with this approach. Foxy is not known for seeing both sides of this picture.
> On 10/7/19 10:48 AM, et...@whidbey.com wrote:
> > I will be replacing practically every cap. Besides all the
> > electrolytics there are some others that, from what I've read about
> > and seen on YouTube, are also suspect.
> > Eric
>
> Caps are cheap. Collateral damages from bad caps are not cheap.
> Replace ALL the electrolytics.
> Replace ALL the paper caps.
>
> Leave the silver dipped micas, tubular ceramics, and any "postage
> stamp" micas alone for the time being.
>
> Replace them one at a time. Take pictures, make notes.
Ceramic tube caps are often paper. A chinese component tester picks up most bad caps, and is supereasy to use. £12 last time I looked.
NT
Fox's Mercantile
Oct 9, 2019, 3:28:36 PM10/9/19
to
Context ya twat.
peterw...@gmail.com
Oct 9, 2019, 3:40:19 PM10/9/19
to
Tabby is dangerous - much as unvaccinated stray cats are dangerous. He loves pissing on the fire.
tabb...@gmail.com
Oct 9, 2019, 4:29:12 PM10/9/19
to
Fox's Mercantile
Oct 9, 2019, 6:03:51 PM10/9/19
to
tabb...@gmail.com
Oct 9, 2019, 6:56:17 PM10/9/19
to
On Wednesday, 9 October 2019 23:03:51 UTC+1, Fox's Mercantile wrote:
> On 10/9/19 3:29 PM, tabbypurr wrote:
> > On Wednesday, 9 October 2019 20:40:19 UTC+1, pf...@aol.com wrote:
> >
> >> Tabby is dangerous - much as unvaccinated stray cats are dangerous. He loves pissing on the fire.
> >>
> >> Peter Wieck
> >> Melrose Park, PA
> >
> > ah the usual bullshitters.
> >
>
> Except, you continually prove it. Repeatedly.
Lol. Plonk for bullsht overload. Life's too short.
> > On Wednesday, 9 October 2019 20:40:19 UTC+1, pf...@aol.com wrote:
> >
> >> Tabby is dangerous - much as unvaccinated stray cats are dangerous. He loves pissing on the fire.
> >>
> >> Peter Wieck
> >> Melrose Park, PA
> >
> > ah the usual bullshitters.
> >
>
> Except, you continually prove it. Repeatedly.
Fox's Mercantile
Oct 9, 2019, 7:02:04 PM10/9/19
to
Don't lie to me.
This makes the 4th or 5th time you claim to have kill
filed me.
This makes the 4th or 5th time you claim to have kill
filed me.
peterw...@gmail.com
Oct 10, 2019, 9:08:42 AM10/10/19
to
It is a wonder that there are still individuals on this planet that are OK with "doing it over" - and over, and over, and over, and over.
Capacitors made in the days of wax and paper, whatever the casing, cardboard, heavier paper, plastic, ceramic, Bakelite and so forth are of-a-piece. That one or even one hundred may be good does not make them any more reliable, or reduce the need to replace them outright - that is, if one cares about the results.
Sure, if I am repairing a shelf-queen for an individual who states, clearly, that the radio will never, ever, be run more than once per year, and then only for five (5) minutes, if at all, and if that individual will run it only on a bench with a controlled power-supply, MAYBE, I will accept instructions only to do that-which-is-minimally-necessary.
This is a hobby for me, so I do not take payment for anything I might do, and I reserve the right to be arbitrary. In general, I wish anything that leaves my hands to be as "safe and effective" as is reasonably possible, and certainly as reliable as possible. Just as I am not required or restricted to using single-weight, non-detergent oil in a vintage automobile, I am not require or restricted to use vintage parts in a vintage radio. Caps are cheap. Even to a hobbyist at $0.40 an hour, they are far cheaper than "Doing it over". Do them all, and be done with it.
Capacitors made in the days of wax and paper, whatever the casing, cardboard, heavier paper, plastic, ceramic, Bakelite and so forth are of-a-piece. That one or even one hundred may be good does not make them any more reliable, or reduce the need to replace them outright - that is, if one cares about the results.
Sure, if I am repairing a shelf-queen for an individual who states, clearly, that the radio will never, ever, be run more than once per year, and then only for five (5) minutes, if at all, and if that individual will run it only on a bench with a controlled power-supply, MAYBE, I will accept instructions only to do that-which-is-minimally-necessary.
This is a hobby for me, so I do not take payment for anything I might do, and I reserve the right to be arbitrary. In general, I wish anything that leaves my hands to be as "safe and effective" as is reasonably possible, and certainly as reliable as possible. Just as I am not required or restricted to using single-weight, non-detergent oil in a vintage automobile, I am not require or restricted to use vintage parts in a vintage radio. Caps are cheap. Even to a hobbyist at $0.40 an hour, they are far cheaper than "Doing it over". Do them all, and be done with it.
amdx
Oct 10, 2019, 12:03:07 PM10/10/19
to
Unless that is a very large resistor or a very small diameter wire...
I just question the value.
Mikek
Ralph Mowery
Oct 10, 2019, 1:09:56 PM10/10/19
to
In article <qnnkni$ga9$1...@dont-email.me>, noj...@knology.net says...
out for an air wound coil that would fit on a 1/2 to 1 watt resistor.
Maybe it was .33 uh.
>
> Know one has mentioned it, but I have a question about the value 33uh.
> Unless that is a very large resistor or a very small diameter wire...
> I just question the value.
>
>
I ran some numbers a while back and nothing reasonable for 33 uH came
> Know one has mentioned it, but I have a question about the value 33uh.
> Unless that is a very large resistor or a very small diameter wire...
> I just question the value.
>
>
out for an air wound coil that would fit on a 1/2 to 1 watt resistor.
Maybe it was .33 uh.
et...@whidbey.com
Oct 10, 2019, 1:22:14 PM10/10/19
to
they are all getting replaced. Aside from probably being a good idea I
really don't want a cap to go short down the road and ruin the power
xmfr. The only caps I am not replacing are the little disc ceramic
ones.
I don't know yet what shape the tubes are in but since the scope
does work now I think they are probably in good shape. The nearest
tube tester to me that I know of is 80 miles away sso I can't test
them except to see ho well the scope functions.
I bet I can find a Ham that has a tube tester closer to me if I
really want to test tubes. Might just be cheaper to find some new ones
on eBay.
Eric
tabb...@gmail.com
Oct 10, 2019, 1:24:18 PM10/10/19
to
NT
Fox's Mercantile
Oct 10, 2019, 1:42:17 PM10/10/19
to
On 10/10/19 12:27 PM, et...@whidbey.com wrote:
> The caps were pretty cheap, even the 450 volt electrolytics. So
> they are all getting replaced. Aside from probably being a good idea I
> really don't want a cap to go short down the road and ruin the power
> xmfr. The only caps I am not replacing are the little disc ceramic
> ones.
Like I said, collateral damage that is avoidable.
> The caps were pretty cheap, even the 450 volt electrolytics. So
> they are all getting replaced. Aside from probably being a good idea I
> really don't want a cap to go short down the road and ruin the power
> xmfr. The only caps I am not replacing are the little disc ceramic
> ones.
> I don't know yet what shape the tubes are in but since the scope
> does work now I think they are probably in good shape. The nearest
> tube tester to me that I know of is 80 miles away sso I can't test
> them except to see ho well the scope functions.
tolerance resistors, then you can worry about the tubes. Which I've
found are usual still good.
> I bet I can find a Ham that has a tube tester closer to me if I
> really want to test tubes. Might just be cheaper to find some new ones
> on eBay.
> Eric
peterw...@gmail.com
Oct 10, 2019, 3:16:14 PM10/10/19
to
No idea where you are, but if you are near Philadelphia, I can help with testing tubes. Between the big Hickok, which can match, or the little Simpson, I would have you covered.
amdx
Oct 10, 2019, 4:26:37 PM10/10/19
to
On 10/10/2019 12:09 PM, Ralph Mowery wrote:
> In article <qnnkni$ga9$1...@dont-email.me>, noj...@knology.net says...
>>
>> No one has mentioned it, but I have a question about the value 33uh.
> In article <qnnkni$ga9$1...@dont-email.me>, noj...@knology.net says...
>>
>> Unless that is a very large resistor or a very small diameter wire...
>> I just question the value.
>>
>>
>
> I ran some numbers a while back and nothing reasonable for 33 uH came
> out for an air wound coil that would fit on a 1/2 to 1 watt resistor.
> Maybe it was .33 uh.
>
>
Ya, I didn't run any numbers, I have wound quite a few air coils and
>> I just question the value.
>>
>>
>
> I ran some numbers a while back and nothing reasonable for 33 uH came
> out for an air wound coil that would fit on a 1/2 to 1 watt resistor.
> Maybe it was .33 uh.
>
>
33uh seems like it would be kind off large, compared to a resistor*. So,
it just doesn't seem right.
Mikek
*I know, how big is a resistor
et...@whidbey.com
Oct 10, 2019, 4:44:15 PM10/10/19
to
Eric
tabb...@gmail.com
Oct 11, 2019, 7:46:35 AM10/11/19
to
On Thursday, 10 October 2019 18:22:14 UTC+1, et...@whidbey.com wrote:
> The caps were pretty cheap, even the 450 volt electrolytics. So
> they are all getting replaced. Aside from probably being a good idea I
> really don't want a cap to go short down the road and ruin the power
> xmfr. The only caps I am not replacing are the little disc ceramic
> ones.
> I don't know yet what shape the tubes are in but since the scope
> does work now I think they are probably in good shape. The nearest
> tube tester to me that I know of is 80 miles away sso I can't test
> them except to see ho well the scope functions.
> I bet I can find a Ham that has a tube tester closer to me if I
> really want to test tubes. Might just be cheaper to find some new ones
> on eBay.
> Eric
Easiest way to test tubes is to check the anode/cathode current in situ. The great majority of bad tubes aren't able to pass enough current, though other faults can exist.
> The caps were pretty cheap, even the 450 volt electrolytics. So
> they are all getting replaced. Aside from probably being a good idea I
> really don't want a cap to go short down the road and ruin the power
> xmfr. The only caps I am not replacing are the little disc ceramic
> ones.
> I don't know yet what shape the tubes are in but since the scope
> does work now I think they are probably in good shape. The nearest
> tube tester to me that I know of is 80 miles away sso I can't test
> them except to see ho well the scope functions.
> I bet I can find a Ham that has a tube tester closer to me if I
> really want to test tubes. Might just be cheaper to find some new ones
> on eBay.
> Eric
NT
Fox's Mercantile
Oct 11, 2019, 9:48:06 AM10/11/19
to
On 10/11/19 6:46 AM, tabb...@gmail.com wrote:
> Easiest way to test tubes is to check the anode/cathode
> current in situ. The great majority of bad tubes aren't
> able to pass enough current, though other faults can exist.
More useless advice.
> Easiest way to test tubes is to check the anode/cathode
> current in situ. The great majority of bad tubes aren't
> able to pass enough current, though other faults can exist.
While this may be true with television sweep tubes used as
RF final amplifiers, the proper way to test tubes "in situ"
is to know what they're supposed to do and see if they do.
Most faults can be zeroed in on by simply seeing if a
function does what it's supposed to do.
peterw...@gmail.com
Oct 11, 2019, 10:38:09 AM10/11/19
to
It is always the device itself that is the best tester of tubes. But for:
Thermal faults - mostly shorts, sometimes going open. A thermal short (or open) will not show up with a VOM when the tube is cold. Further, a rectifier short, for instance, could destroy a power transformer in very short order if not caught immediately, especially if the device is poorly fused (most are). This can be deadly to vintage equipment.
Cascade effects - this tube is a bit weak, and that tube is a bit weak, and yet a third tube is a bit weak. Now, the entire device is 'not quite right' but no singled tube would explain it. And, in the real world, it is this cascade issue that is most common. And, often, why otherwise salvageable devices find their way onto a shelf or into landfill. Sad.
Generally, a thermal fault would have been screened out of the device at some point, one hopes. But not always. And, generally, thermal faults while not immediate are usually quick enough that they would be caught in the initial testing. But not always.
Leads to a tiny rant on how to test a tube. Guys and Gals! Proper tube testing, even on an emissions-only tester, takes _AT LEAST_ ten (10) minutes per tube. First, the set-up and initial screen for shorts and gas. Then the (so-called) "Quality" test. Then, minutes 2 - 10, watch that meter and see what the tube does as it warms up and equalizes. And, at the end of it all, repeat the shorts/gas screening. Only now, do you have useful information.
NOTE 1: Some cheap testers are not capable of holding a heavy output tube for extended periods as the on-board power-supply is inadequate. Be cautious.
Note 2: A tube tester, even the finest Hickok or AVO tests a tube RELATIVE to an established norm or average. A tube may still function perfectly adequately even if all it does is barely lift the meter.
Note 3: Rectifier tubes are the exception to Note 2. They *must* be 'in the zone', or they will be either passing too much AC, or not enough DC, or both.
Note 4: Which leads to being at least aware that the tester in use needs calibration - if possible, or at least pre-testing with known-good tubes to see where the meter falls. Then, compare the others to that.
Tube testers are screening devices. They will indicate dangerous faults (shorts and gas) not possible by any other means other than possible damage to the "home" unit. And they will indicate absolute faults such as an open filament. And for those heavily into Audio, a vanishingly few will allow actual proper matching. After which, it is the "home unit".
A decent emissions-only tester is a handy device for anyone dabbling seriously in tube equipment. IT *may* (not necessarily will) save a bunch of time if used properly. And, a decent emissions tester will not break the bank, either. Leading, again, to:
Note 5: (Heresy Warning!) The step between a decent emissions-only tester and one that will actually convey enough additional information to be useful is considerable in complexity and in cost. A Heath TC3 for 99-44% of general hobby purposes is as good as any but the very top-of-the-line GM testers. That includes the TV-7 military tester and all its clones. The next step up are those capable of matching - or the modern computerized testers that will plot curves and so forth. So, from roughly $80 - $200 for a good, clean TC3 or-equal, to the $900 - $2,500-and-up for a properly calibrated Hickok 539 series, AVO or Card-Matic, don't bother with the in-between.
Thermal faults - mostly shorts, sometimes going open. A thermal short (or open) will not show up with a VOM when the tube is cold. Further, a rectifier short, for instance, could destroy a power transformer in very short order if not caught immediately, especially if the device is poorly fused (most are). This can be deadly to vintage equipment.
Cascade effects - this tube is a bit weak, and that tube is a bit weak, and yet a third tube is a bit weak. Now, the entire device is 'not quite right' but no singled tube would explain it. And, in the real world, it is this cascade issue that is most common. And, often, why otherwise salvageable devices find their way onto a shelf or into landfill. Sad.
Generally, a thermal fault would have been screened out of the device at some point, one hopes. But not always. And, generally, thermal faults while not immediate are usually quick enough that they would be caught in the initial testing. But not always.
Leads to a tiny rant on how to test a tube. Guys and Gals! Proper tube testing, even on an emissions-only tester, takes _AT LEAST_ ten (10) minutes per tube. First, the set-up and initial screen for shorts and gas. Then the (so-called) "Quality" test. Then, minutes 2 - 10, watch that meter and see what the tube does as it warms up and equalizes. And, at the end of it all, repeat the shorts/gas screening. Only now, do you have useful information.
NOTE 1: Some cheap testers are not capable of holding a heavy output tube for extended periods as the on-board power-supply is inadequate. Be cautious.
Note 2: A tube tester, even the finest Hickok or AVO tests a tube RELATIVE to an established norm or average. A tube may still function perfectly adequately even if all it does is barely lift the meter.
Note 3: Rectifier tubes are the exception to Note 2. They *must* be 'in the zone', or they will be either passing too much AC, or not enough DC, or both.
Note 4: Which leads to being at least aware that the tester in use needs calibration - if possible, or at least pre-testing with known-good tubes to see where the meter falls. Then, compare the others to that.
Tube testers are screening devices. They will indicate dangerous faults (shorts and gas) not possible by any other means other than possible damage to the "home" unit. And they will indicate absolute faults such as an open filament. And for those heavily into Audio, a vanishingly few will allow actual proper matching. After which, it is the "home unit".
A decent emissions-only tester is a handy device for anyone dabbling seriously in tube equipment. IT *may* (not necessarily will) save a bunch of time if used properly. And, a decent emissions tester will not break the bank, either. Leading, again, to:
Note 5: (Heresy Warning!) The step between a decent emissions-only tester and one that will actually convey enough additional information to be useful is considerable in complexity and in cost. A Heath TC3 for 99-44% of general hobby purposes is as good as any but the very top-of-the-line GM testers. That includes the TV-7 military tester and all its clones. The next step up are those capable of matching - or the modern computerized testers that will plot curves and so forth. So, from roughly $80 - $200 for a good, clean TC3 or-equal, to the $900 - $2,500-and-up for a properly calibrated Hickok 539 series, AVO or Card-Matic, don't bother with the in-between.
Jeff Urban
Oct 11, 2019, 12:00:26 PM10/11/19
to
Understand electronics much ? Or just what "someone wrote" ?
If you got a coil and cap like that, if the coil is not open it cannot make the trace disappear. It may not have quite the frequency response but it will still work.
There is nothing in a scope that old and limited that would suffer much from the opening up of a resistor that is bridged by a coil. Measure it, if it is not open move on and find the real problem. This ain't it.
If you got a coil and cap like that, if the coil is not open it cannot make the trace disappear. It may not have quite the frequency response but it will still work.
There is nothing in a scope that old and limited that would suffer much from the opening up of a resistor that is bridged by a coil. Measure it, if it is not open move on and find the real problem. This ain't it.
Jeff Urban
Oct 11, 2019, 12:03:53 PM10/11/19
to
>I will be replacing practucally every cap.
You should not until you get the trace to respond to a signal. UNLESS the scope is so old it does not have DC coupling it is not a capacitor.
You should not until you get the trace to respond to a signal. UNLESS the scope is so old it does not have DC coupling it is not a capacitor.
tabb...@gmail.com
Oct 11, 2019, 3:57:46 PM10/11/19
to
Valves declared fauly by a tester sometimes still work. Grid shorts can make little difference when Rfault is higher than Rin, eg when the valve is transformer fed. And valves sometimes pass on a tester but won't work in the circuit. A tester is very useful but not the ultimate decider.
NT
Fox's Mercantile
Oct 11, 2019, 5:17:57 PM10/11/19
to
On 10/11/19 2:57 PM, tabb...@gmail.com wrote:
> Good advice when being thorough, but time consuming. Just checking Ia or Ik is correct is the quick 'is the stage working' check that gets the job done quickly in most cases. If not obviously you then need to check electrode voltages, Rs Cs etc to determine valve or component failure.
>
> Valves declared fauly by a tester sometimes still work. Grid shorts can make little difference when Rfault is higher than Rin, eg when the valve is transformer fed. And valves sometimes pass on a tester but won't work in the circuit. A tester is very useful but not the ultimate decider.
>
>
> NT
You persist in posting wrong or misleading information to defend
> Good advice when being thorough, but time consuming. Just checking Ia or Ik is correct is the quick 'is the stage working' check that gets the job done quickly in most cases. If not obviously you then need to check electrode voltages, Rs Cs etc to determine valve or component failure.
>
> Valves declared fauly by a tester sometimes still work. Grid shorts can make little difference when Rfault is higher than Rin, eg when the valve is transformer fed. And valves sometimes pass on a tester but won't work in the circuit. A tester is very useful but not the ultimate decider.
>
>
> NT
what you original posted that was wrong and/or misleading.
So typical of you.
Service information usually provides voltages that should be
present at various places. With the exception of RF amplifier
stages, I have never seen "Current through this device should
be..."
Almost all low lever signal stages operate well below the
published Ip in tube manuals.
Again the best way to test tubes is "does it work?"
Replacing capacitors to eliminate shorts and high leakage
will solve a majority of problems. Then any "way out of
tolerance" resistors can be replaced. Then you can check
for defective tubes.
Except the obvious ones, cold (open filament) or red plates.
(Obviously something is seriously wrong.)
Ralph Mowery
Oct 11, 2019, 5:46:51 PM10/11/19
to
In article <HOCdnQa9L-bgbD3A...@giganews.com>,
jda...@att.net says...
up and the inside of the glass is silver color and not white. There are
a few exceptions where the tube is ran hard and will get weak. Seems
that the old color TV sets had a bad habit of a couple of tubes in the
horizontal output section getting weak.
jda...@att.net says...
>
> Again the best way to test tubes is "does it work?"
> Replacing capacitors to eliminate shorts and high leakage
> will solve a majority of problems. Then any "way out of
> tolerance" resistors can be replaced. Then you can check
> for defective tubes.
> Except the obvious ones, cold (open filament) or red plates.
> (Obviously something is seriously wrong.)
>
>
>
From what I have seen, tubes are seldom a problem if the filament lights
> Again the best way to test tubes is "does it work?"
> Replacing capacitors to eliminate shorts and high leakage
> will solve a majority of problems. Then any "way out of
> tolerance" resistors can be replaced. Then you can check
> for defective tubes.
> Except the obvious ones, cold (open filament) or red plates.
> (Obviously something is seriously wrong.)
>
>
>
up and the inside of the glass is silver color and not white. There are
a few exceptions where the tube is ran hard and will get weak. Seems
that the old color TV sets had a bad habit of a couple of tubes in the
horizontal output section getting weak.
Fox's Mercantile
Oct 11, 2019, 6:34:05 PM10/11/19
to
On 10/11/19 4:46 PM, Ralph Mowery wrote:
> From what I have seen, tubes are seldom a problem if the filament lights
> up and the inside of the glass is silver color and not white.
Indicating a loss of vacuum, i.e. airleak.
> From what I have seen, tubes are seldom a problem if the filament lights
> up and the inside of the glass is silver color and not white.
The getter is what initially makes the silver deposit on the inside
of the tube envelope.
> There are
> a few exceptions where the tube is ran hard and will get weak. Seems
> that the old color TV sets had a bad habit of a couple of tubes in the
> horizontal output section getting weak.
was a cost savings. And the reason almost every always says "It's
just a bad tube." When in reality, it's almost always capacitors.
tabb...@gmail.com
Oct 12, 2019, 6:51:43 AM10/12/19
to
On Friday, 11 October 2019 22:17:57 UTC+1, Fox's Mercantile wrote:
> Service information usually provides voltages that should be
> present at various places. With the exception of RF amplifier
> stages, I have never seen "Current through this device should
> be..."
then you lack experience. Some cct diags have it printed on, more often there is a cathode R and a stated voltage or a stated anode voltage. V=IR etc. The size of Rk sometimes gives a rough figure.
> Almost all low lever signal stages operate well below the
> published Ip in tube manuals.
>
> Again the best way to test tubes is "does it work?"
which is pretty much what I said. If stage current is within normal bounds, it typically does work.
> Replacing capacitors to eliminate shorts and high leakage
> will solve a majority of problems. Then any "way out of
> tolerance" resistors can be replaced.
yup
> Then you can check
> for defective tubes.
You might. I power it up to check em, and only test tubes when the stage should work but won't.
> Except the obvious ones, cold (open filament) or red plates.
> (Obviously something is seriously wrong.)
or white getter - those are never going to work!
NT
> On 10/11/19 2:57 PM, tabbypurr wrote:
> > Good advice when being thorough, but time consuming. Just checking Ia or Ik is correct is the quick 'is the stage working' check that gets the job done quickly in most cases. If not obviously you then need to check electrode voltages, Rs Cs etc to determine valve or component failure.
> >
> > Valves declared fauly by a tester sometimes still work. Grid shorts can make little difference when Rfault is higher than Rin, eg when the valve is transformer fed. And valves sometimes pass on a tester but won't work in the circuit. A tester is very useful but not the ultimate decider.
> >
> >
> > NT
>
> You persist in posting wrong or misleading information to defend
> what you original posted that was wrong and/or misleading.
> So typical of you.
you sure are the bsing hypocrite.
> > Good advice when being thorough, but time consuming. Just checking Ia or Ik is correct is the quick 'is the stage working' check that gets the job done quickly in most cases. If not obviously you then need to check electrode voltages, Rs Cs etc to determine valve or component failure.
> >
> > Valves declared fauly by a tester sometimes still work. Grid shorts can make little difference when Rfault is higher than Rin, eg when the valve is transformer fed. And valves sometimes pass on a tester but won't work in the circuit. A tester is very useful but not the ultimate decider.
> >
> >
> > NT
>
> You persist in posting wrong or misleading information to defend
> what you original posted that was wrong and/or misleading.
> So typical of you.
> Service information usually provides voltages that should be
> present at various places. With the exception of RF amplifier
> stages, I have never seen "Current through this device should
> be..."
> Almost all low lever signal stages operate well below the
> published Ip in tube manuals.
>
> Again the best way to test tubes is "does it work?"
> Replacing capacitors to eliminate shorts and high leakage
> will solve a majority of problems. Then any "way out of
> tolerance" resistors can be replaced.
> Then you can check
> for defective tubes.
> Except the obvious ones, cold (open filament) or red plates.
> (Obviously something is seriously wrong.)
NT
0 new messages