Troubleshooting Dual Rec,DC voltage on volume pots

[blindsirens]

I have been troubleshooting an older Dual Rectifier and am having a grand time.

First there was popping noises along with a separate loud scratchiness on both channels volume pots. I discovered when the efx loop 12ax is pulled both noises disappear and the amp plays perfectly fine. I substituted known good tubes and it is not the tube but somewhere in its circuit or nearby. As you bring the volume up on either ch I measure DC voltage increasing to anywhere from 8-10volts on the pot. Thus the scratching sound. The DC measures more on the middle tabs heading to the LDRs then the outer one linking to the other pots.

I replaced four caps all in the efx loop circuit and its still there. Plugging a cable into the send or return does not kill the noise. Only bringing the master volume down will silence it or pulling the 12ax out. I've eliminated the tone circuit and even though pulling the loop tube removes it,the voltage is still there with the second relay switching out this section to bypass.

If its not a leaky cap after the master volume then how else could dc voltage arrive at it through the LDR? I don't see a way voltage from the relay could do this.

 

[blindsirens]

Problem solved. There is an area where 200 volts leaves pin 8 of the loop 12ax and hits a resistor and orange cap then continues on. Well right at that eyelet a trace from the LDR runs extremely close to it and continues to the second relay. DC arc'd through(burned) the two points causing what turns out to be alot of dc voltage on the Master volumes. The trace and eyelet had a slight discoloration between them and its also an area where there was a hole punched in the board for a plastic spacer. I simply moved the legs from this resistor and cap over to the following connection and isolated those eyelets on the board. What caused this though I am not sure. I wonder if this area is different on the newer DRs.