Heres a weird one i'm hoping someone can help me with. I've got a TR707 with a very strange power problem. I plugged in the normal Roland 12V power supply and nothing happened so, assuming that it had a broken power jack as all 707's seem to have, i connected my bench power supply to the power socket solder pads on the board and it worked fine. Thinking that this meant the socket was broken i replaced it and plugged in the Roland supply again and still nothing. So i connect the Roland supply to the solder pads and it still doesn't work, but actually connecting my bench power supply to the power connector via a power socket works fine.
Basically this 707 will work fine when powered from my bench power supply, where it draws about 200ma, but it won't work at all from any other plug top power supply, and i've tried about 10 different ones with different polarities and all capable of supplying well over 200ma. Is there some kind of difference between a bench supply and a plug top supply because as far as i can see they are doing exactly the same thing. I've measured the voltage further into the circuit with both a plug top supply and the bench supply and it seems to be identical, it just won't run on any plug top supply.
This one has totally baffled me
UPDATE:
Using the bench supply the voltage regular pins on the 707 board can be measured at 5V-0V-11V. Using any other supply its 0V-0V-11V. So i'm guessing the problem might be something to do with that. The question is, why?