Peavey Classic 30 Reverb headscratcher... - diyAudio
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Old 18th May 2011, 05:18 PM   #1
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Default Peavey Classic 30 Reverb headscratcher...

Zero reverb, no hum when reverb vol is turned up. Tank shows 200 ohms output, no resistance on the input transformer.

Just for grins, I tried the tank through another amp that uses the same in/out impedance for it's tank. Nothing.

Then, I connected the Peavey's reverb send/return to amp B's good tank.....no reverb, no hum.

Tried connecting the foot switch to the Peavey....channel switching works normally, but just getting a "pop" when stomping the reverb switch.

Could I have a double whammy? Bad tank AND bad reverb circuit? Or have I overlooked something??
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Old 18th May 2011, 07:55 PM   #2
M Gregg is offline M Gregg  United Kingdom
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Just a thought,

If this is a spring delay line. Then with volume up if you tap the unit you should hear the spring "rattle". (This shows output is OK).

Did the substitute reverb from amp "b" work after you put it back in the amp "B". Just in case something on amp "A" has stuffed the input Tx.

You say the reverb from amp "a" did not work in "B".

So if you have a fault in amp "A" that may have stuffed the substitute reverb.

So you need to see if you have at least one working reverb unit ?

Find out if amp "A" or "B" work correctly and get a working unit!

Then substitute working parts. If you had a working reverb and now they both do not work you have a fault on amp "A" reverb circuit.

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Old 18th May 2011, 11:29 PM   #3
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Thanks for your reply, M. After reconnecting everything, amp B's reverb is working normally, as before.

With both the tank and the reverb circuit out of operation on the Classic 30, my only guess is that there was a failure in it's reverb circuit that may have damaged the input transformer in the tank.
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Old 19th May 2011, 06:58 AM   #4
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by majortriad View Post
Thanks for your reply, M. After reconnecting everything, amp B's reverb is working normally, as before.

With both the tank and the reverb circuit out of operation on the Classic 30, my only guess is that there was a failure in it's reverb circuit that may have damaged the input transformer in the tank.

Can you post a link to the schematic,

Then we can try a fault find. What do you get if you measure resistance on the working tank input?

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Old 19th May 2011, 02:17 PM   #5
M Gregg is offline M Gregg  United Kingdom
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I guess this is your amp?


http://www.blueguitar.org/new/schem/peavey/c30schem.gif


The reverb is driven by a 4558 OP Amp U1a. If you have a scope you could test terminal J6 to Gnd try playing see if you get anything. Or a start is to test the PSU for the op amp and try changing the 4558. how ever you need to get a known "tank".


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Old 19th May 2011, 04:17 PM   #6
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Thanks for all of your suggestions, M. I've read that the 4558 is often the culprit...they're cheap enough to simply replace. I don't have a scope, so I'm limited in troubleshooting the circuit.

I'll try the IC replacement and go from there. Again. thanks for the help.
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Old 19th May 2011, 04:34 PM   #7
M Gregg is offline M Gregg  United Kingdom
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Yes you could just change the 4558,

You could fit a socket and plug the new one in.

However I would check the power supply for the chip. If its gone faulty, the replacement 4558 may fail again stuffing any new tank!

What resistance is the input to the working tank?

Don't suppose you can get access to the inside of the stuffed tank? ie is it easy to open?

Just for interest..

http://www.paia.com/ProdArticles/hotspuse.htm

OK its not your unit however it gives an idea of what is going on.
Just for fun.



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Old 19th May 2011, 04:53 PM   #8
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working tank reads just over 50 ohms...and I'll be sure to check supply voltage to the 4558
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Old 19th May 2011, 05:05 PM   #9
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by majortriad View Post
working tank reads just over 50 ohms...and I'll be sure to check supply voltage to the 4558
If you can access the stuffed tank. I have found the very fine magnet wire that comes out of the winding sometimes brakes off at the solder joint. Also you could test the transducers and see if you can fix the tank. Then you won't be taking a chance with a new unit.

It's a possible maybe.


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