Hi,
I'm back with another problematic amp, at least to me.

It's a VOX Buckingham V1121, the original problem is:
Normal + Reverb = overall sound level drops, when reverb blend increases.
Brilliant * Reverb = overall sound level drops, when reverb blend increases.
OFF = normal operation, good sound.


I have:

     Replaced the original "1122" reverb tank with a "P-MOD-4AB3C1C" = best spec I could find to equal original.  The original tank had an open reading on one end and needed replacing.
     Replaced all of the electrolytic capacitors. (based on internet research)
     
Now:

Normal + Reverb = loud buzz/noise (can't even leave it on)
Brilliant + Reverb = overall sound level drops, when reverb blend increases. (same)
OFF = normal operation, good sound.

I have attached the schematic, parts list & documentation.

I am not sure where to start, the layout of this circuit is very tight, older and not labeled.
But, I believe someone here can help, based on my last problematic amp.

Any ideas would be greatly appreciated.

Thanks,
Dan

Hi Everyone,
I am new here and I am having a problems with a friend's amp.
I am an electronic technologist by trade and have been repairing all things electronic for many years.
This one has me a little stumped.

They were playing one night, then suddenly this problem occurred.
I notice 1st thing that the 3300uF was loose and defective - replaced it - no change.

I have very low volume level on normal and even lower on override.
I tried Roly's suggestions:
patched send and return = no change
injected music into return = good proper volume overall
injected music into reverb out = good
all voltages = good
have swapped RC4558P's = no change

Somewhere in the preamp area?
Anyone had problems with the TL604CP?
The "Treble/Pull Ch. Select" does select the channels.

I do have an audio probe and can follow the music through the circuit, is there somewhere I can really concentrate on?

I have attached the schematic & User Manual

Any help would be greatly appreciated.

Thanks,
Dan