I have a vintage Doctor Q (mid-70s I’m guessing) that produces no output – it looks like it may have been subjected to someone’s attempt to mod the pedal as there are two large solder blobs and a resistor that’s jumpered on the underside of the PCB.
The good folks at info@ehx.com directed me to ask here. I’m looking for a schematic, a set of probe points, or at least a picture of the internal wiring so i can get a sense of whether this pedal had failed surgery or not.
thanks — i should have been more clear — it’s an EH 4250 B circuit board, which I believe has two stages (there are two trim pots, two op amps, lined up in roughly parallel circuits — and the trimpots are mounted on the top side.
the resistor soldered to the bottom, and the wiring of the bass switch seem to be less than the usual quality of the insides of a 70s EH product. or else this is an even hipper/stranger pedal than i thought!
The resistor on the bottom is likely stock.
It probably needs one or both op-amps changed. Use your meter to make sure the 9v is getting to the board first.
