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Post subject: 65 Super Reverb Amp Running Hot
Posted: Mon Jul 26, 2010 12:50 pm
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I have a 65 Super Reverb amp that is used maybe once or twice every couple years and only for an hour or so. The other day the amp was powered on for about 3 hours and it smelled hot. When I touched the chassis near the on / off switch the chassis was very hot. The amp is completely stock and has only had one or two tubes replaced since I purchased it new in 1965. Any ideas as to what would cause the unit to get this hot?

Thanks...any insight would be most appreciated.

bob


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Posted: Mon Jul 26, 2010 12:58 pm
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Are any of the tubes red-plating (visibly glowing red)?

If so, that's a clue that it requires some maintenance.

It's probably the amp is due for servicing aside from any necessary routine tube replacement. Filter and biasing caps dry out, components bake to the point of cracking, and solder joints sometimes vibrate loose.

Find a competent amp tech familiar with vintage Fenders and give him the amp's bio......he'll know what to do.

Best of luck, HTH

Arjay

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Post subject: 65 Super Reverb Amp Running Hot
Posted: Mon Jul 26, 2010 1:01 pm
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Many thanks for info and the fast response...

bob


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Posted: Mon Jul 26, 2010 8:27 pm
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My first brand new Fender amp was a '67 Super Reverb.

They're great amps!

Arjay

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Post subject: 65 Super Reverb Amp
Posted: Mon Jul 26, 2010 8:32 pm
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Roger that...mine has been a virtual road warrior for its first 30 years. Still to this day has that great sound!


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Posted: Mon Jul 26, 2010 8:35 pm
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All vintage Fender amps have "that great sound".

It's why we love and revere them so.

:mrgreen:

Arjay

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Posted: Tue Jul 27, 2010 5:09 am
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Retroverbial wrote:
All vintage Fender amps have "that great sound".

It's why we love and revere them so.

:mrgreen:

Arjay
I agree,and each one of Leo's amps has it's own character/voice,it seems....just like the old guitars.
They even stayed that way for the first couple of years after the CBS buyout.


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Posted: Tue Jul 27, 2010 8:40 am
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Rebelsoul wrote:
I agree,and each one of Leo's amps has it's own character/voice,it seems.....


+1, RS!

And I've spent the lion's share of the last 33 years trying to convince my wife of that fact.

(the jury's still out)

:mrgreen:

Arjay

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Posted: Wed Aug 11, 2010 9:26 am
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My guess would be the bias caps/circuit.
I had a similar overheating problem when a
solder connection on the bias circuit board failed
onmy old Super.


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Posted: Thu Aug 12, 2010 4:37 am
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Retroverbial wrote:
Are any of the tubes red-plating (visibly glowing red)?


Can you explain this a bit more? I thought tubes were suppose to glow.

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Posted: Thu Aug 12, 2010 6:03 am
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Tubes do glow but the plates shouldn't be glowing red,if you're not sure what the plates are,look at some diagrams of a vacuum tube to see the parts.
The heater is what you usually see glowing an orange color.


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Posted: Thu Aug 12, 2010 8:53 am
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Rebelsoul wrote:
Tubes do glow but the plates shouldn't be glowing red,if you're not sure what the plates are,look at some diagrams of a vacuum tube to see the parts.
The heater is what you usually see glowing an orange color.


Will do, after reading your post I took a look at my tubes and they were glowing orange (vs red as you said in your earlier post) and just wanted to double check. Thanks!

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Posted: Sun Aug 15, 2010 10:24 am
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If you look at the photo, in the first link, you'll see one 7591 glowing kinda "purple" (due to te way the camera took the photo) on the large metal surfaces of the tube. These are the anode plates. Notice how the 7951 on the right is not glowing? This indicates that the one tube is running too hot.

The second photo shows "hot spots"--- those white areas on some of the plates. This can be just as dangerous as "red plates." Even if the rest of the plate shows no signs of overheating.

HTH!


http://www.mindspring.com/~insomniaskun ... amp2-b.jpg

http://www.mindspring.com/~insomniaskun ... amp2-a.jpg


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Posted: Fri Aug 27, 2010 5:48 am
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The tubes you should check for glowing are the 6L6s.
They should glow blue with the amp operating.
Any red or orange, and the heat you've noticed, may be
due to bias circuit failure or perhaps underbiasing if somebody
was tooling around with the bias control pot.


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