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A guide to fuse replacement
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bitrex
Feb 28, 2018, 11:27:10 AM2/28/18
to
John-Del
Feb 28, 2018, 12:34:06 PM2/28/18
to
On Wednesday, February 28, 2018 at 11:27:10 AM UTC-5, bitrex wrote:
> <https://imgur.com/a/aMsBA>
Many moons ago I had a guy bring in a stereo receiver for repair. The cover was off so he could show me where the fuses went.. He also had a 5 pack of Radio Shack fuses and just one remained. He told me he changed the fuse four times and it blew immediately each time.
I asked him why he stopped at 4..
> <https://imgur.com/a/aMsBA>
Many moons ago I had a guy bring in a stereo receiver for repair. The cover was off so he could show me where the fuses went.. He also had a 5 pack of Radio Shack fuses and just one remained. He told me he changed the fuse four times and it blew immediately each time.
I asked him why he stopped at 4..
Trevor Wilson
Feb 28, 2018, 2:46:14 PM2/28/18
to
--
Trevor Wilson
www.rageaudio.com.au
Mike Coon
Feb 28, 2018, 3:56:01 PM2/28/18
to
In article <6eebb976-be86-4c52...@googlegroups.com>,
ohg...@gmail.com says...
Is it like keeping one bullet to avoid being captured alive?
Mike.
ohg...@gmail.com says...
Mike.
Gareth Magennis
Feb 28, 2018, 4:02:18 PM2/28/18
to
"bitrex" wrote in message news:rLAlC.237600$9z2.1...@fx43.iad...
<https://imgur.com/a/aMsBA>
*******************************************
I recently keep coming across brand new unsold equipment which has been
supplied with a fast blow mains fuse that has blown at turn on.
This is from more than one manufacturer.
I have no idea what that is all about.
Gareth.
John-Del
Feb 28, 2018, 6:08:55 PM2/28/18
to
I had a guy bring in a Thomson TX82 13" TV for a dead complaint. In it's fuse holder was a piece of copper tubing cut to fit a GMA fuse holder perfectly. Missing from the TV was in the mains input reactor filter coil. There were four burn marks where the posts used to be mounted to the board. I would love to know how big a bang this made when they plugged it in.
Adrian Caspersz
Feb 28, 2018, 6:09:20 PM2/28/18
to
On 28/02/18 21:02, Gareth Magennis wrote:
>
> I recently keep coming across brand new unsold equipment which has been
> supplied with a fast blow mains fuse that has blown at turn on.
>
> This is from more than one manufacturer.
>
> I have no idea what that is all about.
>
Second customer returns after a returned "repair" done with the wrong fuse?
>
> I recently keep coming across brand new unsold equipment which has been
> supplied with a fast blow mains fuse that has blown at turn on.
>
> This is from more than one manufacturer.
>
> I have no idea what that is all about.
>
If that's true, you would do well to investigate who is actually doing
this. What class of equipment?
--
Adrian C
Phil Allison
Feb 28, 2018, 6:25:17 PM2/28/18
to
Gareth Magennis wrote:
---------------------------
T fuses were not always easy to buy, so it was common to use an oversize F fuse instead - labelling often encouraged you to do so.
Whatever the combination of dumb ideas, it is not hard to do a number of on-off cycles while keeping a close eye on an F fuse. If it bends severely at switch on it's gonna fail soon.
.... Phil
---------------------------
>>
> I recently keep coming across brand new unsold equipment which has been
> supplied with a fast blow mains fuse that has blown at turn on.
>
> This is from more than one manufacturer.
>
** A friend who did Fender warranty work was getting a lot "failed on the showroom floor" amps. Always the same, an F1A or F1.6A supply fuse popped. Fitted a T fuse instead and no more problem. Of course, the fuses concerned were buried inside on the main PCB !!
> I recently keep coming across brand new unsold equipment which has been
> supplied with a fast blow mains fuse that has blown at turn on.
>
> This is from more than one manufacturer.
>
T fuses were not always easy to buy, so it was common to use an oversize F fuse instead - labelling often encouraged you to do so.
Whatever the combination of dumb ideas, it is not hard to do a number of on-off cycles while keeping a close eye on an F fuse. If it bends severely at switch on it's gonna fail soon.
.... Phil
Gareth Magennis
Feb 28, 2018, 7:11:03 PM2/28/18
to
"Phil Allison" wrote in message
news:d0463157-c0a6-4f41...@googlegroups.com...
Fender is one culprit.
Most others are Active studio monitors of various brands.
Gareth.
Phil Allison
Feb 28, 2018, 11:02:12 PM2/28/18
to
Gareth Magennis wrote:
----------------------
>
> >
> > I recently keep coming across brand new unsold equipment which has been
> > supplied with a fast blow mains fuse that has blown at turn on.
> >
> > This is from more than one manufacturer.
> >
>
> ** A friend who did Fender warranty work was getting a lot "failed on the
> showroom floor" amps. Always the same, an F1A or F1.6A supply fuse popped.
> Fitted a T fuse instead and no more problem. Of course, the fuses concerned
> were buried inside on the main PCB !!
>
> T fuses were not always easy to buy, so it was common to use an oversize F
> fuse instead - labelling often encouraged you to do so.
>
> Whatever the combination of dumb ideas, it is not hard to do a number of
> on-off cycles while keeping a close eye on an F fuse. If it bends severely
> at switch on it's gonna fail soon.
>
>
----------------------
>
> >
> > I recently keep coming across brand new unsold equipment which has been
> > supplied with a fast blow mains fuse that has blown at turn on.
> >
> > This is from more than one manufacturer.
> >
>
> ** A friend who did Fender warranty work was getting a lot "failed on the
> showroom floor" amps. Always the same, an F1A or F1.6A supply fuse popped.
> Fitted a T fuse instead and no more problem. Of course, the fuses concerned
> were buried inside on the main PCB !!
>
> T fuses were not always easy to buy, so it was common to use an oversize F
> fuse instead - labelling often encouraged you to do so.
>
> Whatever the combination of dumb ideas, it is not hard to do a number of
> on-off cycles while keeping a close eye on an F fuse. If it bends severely
> at switch on it's gonna fail soon.
>
>
> ********************************
>
>
> Fender is one culprit.
>
> Most others are Active studio monitors of various brands.
>
** I assume the fuses supplied ARE as marked on the schems and PCBs ?
>
>
> Fender is one culprit.
>
> Most others are Active studio monitors of various brands.
>
The Fender HR Deluxe, 40W all tube amp, comes supplied with F1.6A
fuses fitted for 230/240VAC use.
https://schematicheaven.net/fenderamps/hotrod_deluxe.pdf
Despite the NTC device, the fuse value is right on the limit for
tolerating worst case, inrush surges.
With such amps, the power transformer surges hard when the AC supply is
switched on near a supply voltage zero crossing - plus tube heaters draw
significant extra current when first turned on ( about 6 times the rated
amount ) and lastly the filter electros caps surge if the supply is switched
near a supply voltage peak.
A last straw step happens when the operator flicks the AC switch on then off and quickly on again - as could easily happen playing about with an unfamiliar amp in a store. Surging the delicate F fuse wire while it is still hot.
>
> Most others are Active studio monitors of various brands.
>
.... Phil
Phil Allison
Feb 28, 2018, 11:18:07 PM2/28/18
to
Adrian Caspersz wrote:
----------------------
>
> >
> > I recently keep coming across brand new unsold equipment which has been
> > supplied with a fast blow mains fuse that has blown at turn on.
> >
> > This is from more than one manufacturer.
> >
> > I have no idea what that is all about.
> >
>
> Second customer returns after a returned "repair" done with the wrong fuse?
>
> If that's true, you would do well to investigate who is actually doing
> this.
** Factory techs working in places like Mexico and China, sometimes elsewhere.
> What class of equipment?
** Anything that has a significant inrush surge.
Toroidal transformer based PSUs are major culprits.
.... Phil
----------------------
>
> >
> > I recently keep coming across brand new unsold equipment which has been
> > supplied with a fast blow mains fuse that has blown at turn on.
> >
> > This is from more than one manufacturer.
> >
> > I have no idea what that is all about.
> >
>
> Second customer returns after a returned "repair" done with the wrong fuse?
>
> If that's true, you would do well to investigate who is actually doing
> this.
> What class of equipment?
** Anything that has a significant inrush surge.
Toroidal transformer based PSUs are major culprits.
.... Phil
N_Cook
Mar 1, 2018, 3:45:45 AM3/1/18
to
Phil Allison
Mar 2, 2018, 2:29:55 AM3/2/18
to
Nutcase Kook wrote:
-------------------
Gareth Magennis wrote:
> > *******************************************
> >
> > I recently keep coming across brand new unsold equipment which has been
> > supplied with a fast blow mains fuse that has blown at turn on.
> >
> > This is from more than one manufacturer.
> >
> > I have no idea what that is all about.
> >
>
>
>
The problem is "inrush surge" which nearly every common appliance exhibits.
About the only types of appliance that have no switch on surge are resistance heaters for food, water and air - plus the common soldering tool.
FYI:
peak and RMS current values measured for some 240VAC items.
4A > .25A 60W incandescent lamp
12A > 7A 700W microwave
20A > .1A 15W CFL
52A > .55A colour CRT monitor
55A > 1.6A 1980s 100W Marshall
.... Phil
-------------------
Gareth Magennis wrote:
> > *******************************************
> >
> > I recently keep coming across brand new unsold equipment which has been
> > supplied with a fast blow mains fuse that has blown at turn on.
> >
> > This is from more than one manufacturer.
> >
> > I have no idea what that is all about.
> >
>
>
>
> Universal self-selecting SMPS , with fuses supplied for 110V countries?
>
** IME, fuse current ratings for 120VAC use are exactly double what one needs for 240VAC use. See that a lot.
>
The problem is "inrush surge" which nearly every common appliance exhibits.
About the only types of appliance that have no switch on surge are resistance heaters for food, water and air - plus the common soldering tool.
FYI:
peak and RMS current values measured for some 240VAC items.
4A > .25A 60W incandescent lamp
12A > 7A 700W microwave
20A > .1A 15W CFL
52A > .55A colour CRT monitor
55A > 1.6A 1980s 100W Marshall
.... Phil
Ralph Mowery
Mar 3, 2018, 5:54:29 PM3/3/18
to
In article <d0463157-c0a6-4f41...@googlegroups.com>,
palli...@gmail.com says...
3AG type fuse. While the fuse was rated fine for the current ( about 5
amps more than the current drain), after about a month it would do what
I call a 'sag out'. The element would just be bent to the bottom of
the glass and quit making connection.
I guess that the contacts for the plug in with a twist lock cap was not
making contact well enough to keep the heat down.
The current would cycle from almost no current to full current about 20
or more times a day on the average.
palli...@gmail.com says...
>
> T fuses were not always easy to buy, so it was common to use an oversize F fuse instead - labelling often encouraged you to do so.
>
> Whatever the combination of dumb ideas, it is not hard to do a number of on-off cycles while keeping a close eye on an F fuse. If it bends severely at switch on it's gonna fail soon.
>
>
>
>
I had a solid state amplifier for my ham gear that used a 20 or 25 amp
> T fuses were not always easy to buy, so it was common to use an oversize F fuse instead - labelling often encouraged you to do so.
>
> Whatever the combination of dumb ideas, it is not hard to do a number of on-off cycles while keeping a close eye on an F fuse. If it bends severely at switch on it's gonna fail soon.
>
>
>
>
3AG type fuse. While the fuse was rated fine for the current ( about 5
amps more than the current drain), after about a month it would do what
I call a 'sag out'. The element would just be bent to the bottom of
the glass and quit making connection.
I guess that the contacts for the plug in with a twist lock cap was not
making contact well enough to keep the heat down.
The current would cycle from almost no current to full current about 20
or more times a day on the average.
olds...@tubes.com
Mar 4, 2018, 4:35:30 AM3/4/18
to
On Sat, 3 Mar 2018 17:54:19 -0500, Ralph Mowery
<rmower...@earthlink.net> wrote:
>I had a solid state amplifier for my ham gear that used a 20 or 25 amp
>3AG type fuse. While the fuse was rated fine for the current ( about 5
>amps more than the current drain), after about a month it would do what
>I call a 'sag out'. The element would just be bent to the bottom of
>the glass and quit making connection.
>
>I guess that the contacts for the plug in with a twist lock cap was not
>making contact well enough to keep the heat down.
>
>The current would cycle from almost no current to full current about 20
>or more times a day on the average.
I'm not sure if this is about power line fuses or 12Volt, or something
<rmower...@earthlink.net> wrote:
>I had a solid state amplifier for my ham gear that used a 20 or 25 amp
>3AG type fuse. While the fuse was rated fine for the current ( about 5
>amps more than the current drain), after about a month it would do what
>I call a 'sag out'. The element would just be bent to the bottom of
>the glass and quit making connection.
>
>I guess that the contacts for the plug in with a twist lock cap was not
>making contact well enough to keep the heat down.
>
>The current would cycle from almost no current to full current about 20
>or more times a day on the average.
in the circuit. If this is a for a 120VAC line, you are possibly already
overloading the house fuse or breaker.
As far as that sag in the fuses, I'd suggest using a SLOW-BLOW fuse.
They are made to handle high starting current. Or switch to a breaker.
Of course there could be a defect in the amplifier too, such as a
failing power supply capacitor.
Knowing more about the application for the fuse would make it easier to
suggest what could be wrong.
Terry Schwartz
Mar 4, 2018, 9:02:15 AM3/4/18
to
Oh yes please, we're all waiting on pins and needles for your suggestions.
Ralph Mowery
Mar 4, 2018, 9:57:34 AM3/4/18
to
In article <h9fn9d1h3vol0oadn...@4ax.com>,
olds...@tubes.com says...
The application was for an amplifier for a 2 meter repeater. The amp
is a solid state and operates at a nominal 12 volts DC. I think it had
a 25 amp fuse and operated at 20 amps. The holder was a panel mounted
with the cap on it that you give about a half turn to remove.
The amp draws almost no current when in standby and the full 20 amps
when activated . The amp; did not have any devective capacitors and the
ones in it were only a few MFD at the most and they would only have
about 12 volts on them.
The amp was fed with a seperate 12 volt supply that was rated for over
30 amps.
olds...@tubes.com says...
is a solid state and operates at a nominal 12 volts DC. I think it had
a 25 amp fuse and operated at 20 amps. The holder was a panel mounted
with the cap on it that you give about a half turn to remove.
The amp draws almost no current when in standby and the full 20 amps
when activated . The amp; did not have any devective capacitors and the
ones in it were only a few MFD at the most and they would only have
about 12 volts on them.
The amp was fed with a seperate 12 volt supply that was rated for over
30 amps.
pf...@aol.com
Mar 4, 2018, 2:09:25 PM3/4/18
to
Coming very late into this....
Fuses are very simple beasts made complicated by a fundamental lack of understanding.
a) The nature of the load. A purely resistance load is entirely different from a motor load. Both of which are different from a filament load.
b) How inrush current works. A purely resistance load has a massive inrush until the resistance element heats up - whereupon the load drops in proportion to the temperature. An AA5, for instance, is essentially a dead-short at turn-on. As are most tube loads.
c) The differences between motor loads, filament loads and electronic loads.
d) Rated Operating Voltage. Fuses rated below 240V are to be taken with much salt.
e) The differences between a standard fuse, a fast fuse, a slow-blow fused and a dual-element fuse. READ THE OPERATION TABLES!
And, unless you have no investment in the connected load or its fate whatsoever, eliminate all slow-blow AGC fuses from consideration - full stop (the one with the wire element wound around a ceramic rod)!!
From here, do your own research. For the power-supply in question, I would suggest starting with a 20A DE Fuse rated at 250V. NOTE: Many AGC fuses are rated at only 32V. Avoid them. If this blows consistently, only then would I suggest moving to a 25A DE Fuse.
Peter Wieck
Melrose Park, PA
Fuses are very simple beasts made complicated by a fundamental lack of understanding.
a) The nature of the load. A purely resistance load is entirely different from a motor load. Both of which are different from a filament load.
b) How inrush current works. A purely resistance load has a massive inrush until the resistance element heats up - whereupon the load drops in proportion to the temperature. An AA5, for instance, is essentially a dead-short at turn-on. As are most tube loads.
c) The differences between motor loads, filament loads and electronic loads.
d) Rated Operating Voltage. Fuses rated below 240V are to be taken with much salt.
e) The differences between a standard fuse, a fast fuse, a slow-blow fused and a dual-element fuse. READ THE OPERATION TABLES!
And, unless you have no investment in the connected load or its fate whatsoever, eliminate all slow-blow AGC fuses from consideration - full stop (the one with the wire element wound around a ceramic rod)!!
From here, do your own research. For the power-supply in question, I would suggest starting with a 20A DE Fuse rated at 250V. NOTE: Many AGC fuses are rated at only 32V. Avoid them. If this blows consistently, only then would I suggest moving to a 25A DE Fuse.
Peter Wieck
Melrose Park, PA
tabb...@gmail.com
Mar 4, 2018, 2:49:12 PM3/4/18
to
On Sunday, 4 March 2018 19:09:25 UTC, pf...@aol.com wrote:
> Coming very late into this....
>
> Fuses are very simple beasts made complicated by a fundamental lack of understanding.
indeed
> Coming very late into this....
>
> Fuses are very simple beasts made complicated by a fundamental lack of understanding.
> a) The nature of the load. A purely resistance load is entirely different from a motor load. Both of which are different from a filament load.
> b) How inrush current works. A purely resistance load has a massive inrush until the resistance element heats up - whereupon the load drops in proportion to the temperature.
> An AA5, for instance, is essentially a dead-short at turn-on. As are most tube loads.
> c) The differences between motor loads, filament loads and electronic loads.
> d) Rated Operating Voltage. Fuses rated below 240V are to be taken with much salt.
> e) The differences between a standard fuse, a fast fuse, a slow-blow fused and a dual-element fuse. READ THE OPERATION TABLES!
Then there's breaking capacity, a rather important thing especially with mains fuses.
> And, unless you have no investment in the connected load or its fate whatsoever, eliminate all slow-blow AGC fuses from consideration - full stop (the one with the wire element wound around a ceramic rod)!!
NT
Phil Allison
Mar 4, 2018, 8:36:52 PM3/4/18
to
pf...@aol.com wrote:
---------------------
Many blown fuses look perfectly OK, needing a continuity test to prove the point. Ceramic case fuses for one.
Blown fuses deserve a careful inspection, to make sure the right amp rating and type ( F or T) was installed. Don't ya hate folk who toss them away, sometimes along with the fuse cap.
.... Phil
---------------------
>
>
> Fuses are very simple beasts made complicated by a fundamental
> lack of understanding.
>
** Fuses only seem simple ......
>
> Fuses are very simple beasts made complicated by a fundamental
> lack of understanding.
>
Many blown fuses look perfectly OK, needing a continuity test to prove the point. Ceramic case fuses for one.
Blown fuses deserve a careful inspection, to make sure the right amp rating and type ( F or T) was installed. Don't ya hate folk who toss them away, sometimes along with the fuse cap.
.... Phil
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