DV Mark DV40 112 40W Combo Reverb Volume Issue

[misterc57]

DV Mark DV40 112 40W 1x12 Tube Guitar Combo Amp

DV Mark DV40 112 40W Combo Reverb Volume Issue

Received this amp in trade. Issue is that the reverb is acting like a volume control.

If reverb knob is at zero there is no volume. Turn the knob slightly above 1 and reverb is now FULL ON deep and crazy, and amp has output.

I cleaned every pot and tube socket. All tubes test good. Reverb pot is functioning as it should, appears to be a 20k pot, and measures correct going up and down the pot.

Schematic and suggestions needed.

If I take the reverb tank out of the loop, there is barely any volume from the amp and the sound is distorted.

I have attached a block diagram from the owners manual.

Thank you, MC

[misterc57]

I have now discovered a second issue which may or may not relate to the first issue.

I plugged another amp's pre-amp out into the amp-in jack. When I play the guitar from the other amp connected this way, all notes strummed moderate to hard distort badly. Too rule out the speaker, I tried connecting to a different speaker cab and the same thing happens.

MC

[misterc57]

More discovery

I have bypassed the reverb tank with an rca cable going to the in/out on the pre-amp board.

If reverb knob is at zero there is no volume. Turn the knob slightly to 1 and volume is way too loud and overall volume increases as you keep turning up the reverb knob.

Pre-out to another amp works fine. All controls before reverb function as they should. Reverb is just after pre-out in block diagram.

[52 Bill]

If reverb knob is at zero there is no volume. Turn the knob slightly to 1 and volume is way too loud and overall volume increases as you keep turning up the reverb knob.

The way most amps work, is the reverb signal is mixed with the straight signal. It sounds like the straight signal is missing from your mix.

The block diagram does not have any circuit details, so I can't suggest anything more than to see if you can find where the straight signal splits off to the input of the reverb drive circuit and to the mixer stage. Then try and find out why you do not have any straight signal.

[misterc57]

DV Mark was very helpful. Led me to bad R48 on pre-amp board. Problem fixed.

Thank you!