I recently came into this pedal in non-working condition. All original 1978 grey box DOD 250 overdrive preamp
Bypassed signal was fine, but the unit had no drive output. Switch and voltages checked out ok, so I dug out my signal generator and oscilloscope. Trace signal was getting to the input of the op amp, but the amp had nothing on the output.
I opted to add a socket when I removed the old UA741CP. This will make experimenting with different chips a lot eisier in the future!
I replaced the op amp with an SK equivalent SK3552 (made in Italy) that I had on hand. Now this thing sounds awesome! Ready to rock for another 35 years