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Post subject: 65 Fender Deluxe Reverb...Blowing Fuses...Need Help Plz
Posted: Thu Jan 26, 2017 1:55 am
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I am helping a buddy fix his original 65 Fender Reverb. He has never played on it. It keeps blowing the Slo Blow Fuse 1amp after being turned on for 30 seconds.

All tubes and rectifier and all filter caps are the originals

Here is the info I found online thats helped me and also made me ask some questions:

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Here's how Gerry Weber tested an amp, using the light-bulb limiter. Remember, this is for testing an amp that is blowing fuses. One purpose of the light-bulb is to allow you to keep the amp on - without blowing a fuse - long enough to troubleshoot it. He suggested using a 100 watt bulb.

Plug the amp in to the light-bulb limiter, turn it on in 'standby' mode (if available)
Question: Does the Standby Switch flipped up towards "Standby" mean its in standby mode or play mode?
Switch standby to 'play'. If the lamp lights brightly, this indicates a short somewhere in the amp.

Remove power tubes, one at a time. If the light stays bright, that tube can be replaced in the amp. If the light dims, the tube you just removed is shorted. If none of the tubes appears to be shorted, go to the next step.

Remove all power tubes together. If the light dims, the problem is probably in the bias supply.
This is what it did...so whats a bias supply and how do I check it???

If the light remains bright, the problem is (probably) a bad rectifier, shorted power transformer, or shorted filter cap - see next step.

Now switch the amp to standby mode. If the light goes out, the problem is in the filter caps. If the light keeps shining bright, the problem is is the transformer or the rectifier - see next step.

Remove the rectifier (or disconnect the diodes if it's a hard-wired solid-state rectifier). If the light dims, the rectifier is bad. If the light stays bright, the problem is probably in the power transformer.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Here is what we have done: Bench test done out of amp box with no wires or speaker connected

1.We made one of those Gerry Voltage Limiter...cord, outlet, 100watt bulb and base.
2. Tested all small glass tubes...the 2 medium size 6v6...and the rectifier GZ34...all Test Good
(Ol friend of mine has lots of Original Old Tubes in the Box and Test equip...seasoned electronics repairman)
3.NOT CONNECTED TO CURRENT LIMITER and all tubes and rectifier pulled out and it doesn't blow fuse.
Only connecting rectifier will blow the fuse
4. Connected to Current Limiter and taking out one tube at a time and replacing it doesn't make light bulb dimmer. Taking them all out makes light dimmer. So going by the Gerry Current Limiter guidelines...that tells me its a problem with my bias supply. What is my bias supply and how to I check it?

5. We checked standby switch and ground switch...ALL GOOD
6. After hours of testing We plugged in amp with all parts reinstalled straight to wall outlet...NO LIMITER... and amp stayed on for about 1 minute...but then some hissing and some light smoke came out. It was one of the filter caps that had leaked some juice...i believe it was the one that supposedly supplies the rectifier
Could this had the problem all along? I hear that the life of these are 10 years max...so these were born in 1965

Any help is greatly appreciated.

My buddy is going to order some new filter caps keeping the original size for all...i think 15's or all 16's


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Post subject: Re: 65 Fender Deluxe Reverb...Blowing Fuses...Need Help Plz
Posted: Thu Feb 09, 2017 2:35 am
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Joined: Wed Mar 31, 2010 12:48 am
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Bolio wrote:
What is my bias supply and how to I check it?


:shock:

You have absolutely no business whatsoever trying to troubleshoot and repair that amp, unless you're merely bound and determined to destroy it or kill yourself (or both).

You wanted help, I just gave you the best that you're ever gonna get.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 65 Fender Deluxe Reverb...Blowing Fuses...Need Help Plz
Posted: Thu Feb 09, 2017 3:31 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14045
Location: Province de Québec, Canada
Retroverbial wrote:
Bolio wrote:
What is my bias supply and how to I check it?


:shock:

You have absolutely no business whatsoever trying to troubleshoot and repair that amp, unless you're merely bound and determined to destroy it or kill yourself (or both).

You wanted help, I just gave you the best that you're ever gonna get.

Arjay


+1

Amps need to see a qualified tech.


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