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fading reverb

4/28/2004 9:54 AM
Barry Jackson
fading reverb
I've just got myself an old Guild RT-98 amp from 1962, I think. It has a spring reverb. The reverb is apt to fade away from time to time. It comes back on if the amp is switched to standby for a minute or two, but then fades away again.  
Any thoughts as to the likely cause?
4/30/2004 10:28 PM
Dai Hirokawa

i would guess a bad solder connection some where which "comes back" when you switch off/then on the standby, which sends a surge through the bad connection bringing it back until it goes bad again. So try to locate and re-solder.
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5/1/2004 8:34 PM
Barry Jackson

Cheers Dai, I'll get checking
5/1/2004 3:12 AM
Check the reverb driver tube with a good tube checker. It could be on its last legs. Seems to potentially have bad cathode emissions.  
5/1/2004 8:33 PM
Barry Jackson

Thanks AngelBoy, I'll check the tube
5/4/2004 2:37 PM
Mark Hammer

The paper caps may be more than 42 years old and you're wondering why it's fading? Time may heal wounds, but it sure doesn't work wonders for caps. The fact that changes in the power supply and time-on will effect the reverb signal suggest to me that caps may well be involved. Any time some outcome depends on time, then it either reflects heat build-up or some accumulating charge.
5/4/2004 10:25 PM

Time wounds all heels.
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