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FDP Forum / Fender Amps: Vintage (before 1985) / FENDER CIRCUIT BREAKER 010872

telefender

canada

fender50
Apr 29th, 2018 12:06 PM   Edit   Profile  

Have a 74 PR and the circuit breaker by the power transform appears to have shorted out ....can these be replaced ? Cannot find any information on this type of fuse ..... stamped on bottom of amp chassis " Replace only with red 010872 circuit breaker . What does this circuit breaker do ? what does it protect ? Need any info possible ....thnks

stl80
Contributing Member
*********

USA

stl80
Apr 29th, 2018 02:39 PM   Edit   Profile  

Take the short out and put a long in. : > )
Jim

telefender

canada

fender50
Apr 29th, 2018 07:05 PM   Edit   Profile  

HA HA ...funny ....

Checked my 68 PR and it does not have this protective type of circuit breaker ....does not have anything of this nature by the power transformer. This must be some type of thermal cutoff that appears to be wire wound like a choke.
Must be a thermal cutoff fuse of some sort. Indicates to only replace with " red" component.

willie

Too Near Atlanta GA

Amp Tech Emeritus
Apr 30th, 2018 07:38 AM   Edit   Profile  

It is indeed a "thermal protector" but I believe what it was supposed to do was limit in rush current. It has an nominal resistance at cold start up that reduces as it heats which is supposed to limit the amount of current that can be drawn at start up. It is questionable why the amp needs this in the first place. This was a CSA requirement for production approval. There are newer replacements such as the FMIC C60 thermistor but it isn't a drop in replacement.

w

(This message was last edited by willie at 09:49 AM, Apr 30th, 2018)

telefender

canada

fender50
Apr 30th, 2018 02:46 PM   Edit   Profile  

OK....great thanks for the info . The amp started to hum loudly and then the fuse at the back burned out. I replace the fuse ...but only to find that the amp would not turn on ....so in doing some checking I noted this thermal protector switch was open when I tested with a continuity tester. I was using this amp that has a 10 inch 8 ohm speaker with an extension cabinet that only had a 4 ohm speaker load . Hope this didn't cause the power tranny to burn or short out?

stl80
Contributing Member
*********

USA

stl80
Apr 30th, 2018 03:13 PM   Edit   Profile  

If it was open, it already has a long in it, put in a short. : > )
Jim


telefender

canada

fender50
Apr 30th, 2018 04:57 PM   Edit   Profile  

YOU GUYS ARE 2 FUNNY ... but doe not solve the problem..... have inquired into the Fender thermistor as advised by Willie (who seems to be the only one that can relate) and it appears to be a possibility . thnks

Pinetree
Moderator Emeritus
(with many stars)

NW Pennsylvania

Apr 30th, 2018 06:12 PM   Edit   Profile  

Willie - former amp tech.


Everyone else - amateur comedians.


Hope this helps.



willie

Too Near Atlanta GA

Amp Tech Emeritus
Apr 30th, 2018 06:32 PM   Edit   Profile  

Actually...I'm still doing amp work, just working on what I want to and when I want to which is my idea of retirement. :-)

Doubtful that the output load mismatch cause such a catastrophic failure. Sounds more like a cap failure or perhaps a screen resistor or tube short, just to name a few likely causes. It is clear though that something caused your amp to draw too much current which blew the fuse and caused the thermal protector to open.

w

Pinetree
Moderator Emeritus
(with many stars)

NW Pennsylvania

Apr 30th, 2018 06:44 PM   Edit   Profile  

Willie - Amp Tech Emeritus


But only sorta.



willie

Too Near Atlanta GA

Amp Tech Emeritus
Apr 30th, 2018 08:05 PM   Edit   Profile  

Exactly...freedom to choose...priceless.

w

telefender

canada

fender50
Apr 30th, 2018 11:42 PM   Edit   Profile  

wELL....WILLIE you and I have something in common.
I'm retired too ...and I choose what to do / when to do it and how to do it!

Am taking the amp to another amp guru who like yourself seems to think that the amp is still salvageable. I have to get this thermistor ...which is $6.79 at Darren Rileys.com ..but another $25 to ship to Canada....well I need it so what the hell !!
Take care and thanks again for the info ....will check the screen resistor/ caps and the tube for a short ... . and will let you know the results.

willie

Too Near Atlanta GA

Amp Tech Emeritus
May 1st, 2018 11:57 AM   Edit   Profile  

Most certainly a very serviceable and fixable amp and well worth it as well. Darren Riley is a good source though that is hellacious for shipping. Any experienced amp tech will go looking for the cause of the failure before firing the amp up with new parts in it.

Best of luck with it...and enjoy being...just being. ;)

w


Roly
Contributing Member
**********
**********
****

Whitehorse Canada

I don't get out much
May 1st, 2018 03:33 PM   Edit   Profile  

I have one or two kicking around. I'm in Canada.
PM me.
cheers

FDP Forum / Fender Amps: Vintage (before 1985) / FENDER CIRCUIT BREAKER 010872




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