Reference supply is working now

I've been working on the reference power supply. It uses one of the dual amplifier modules that is pretty much identical to the rest of the ones in the machine and a module with a heated zener diode and a couple power transistors for current boost. The positive supply worked fine, but the negative was pegged at -15V. It should be -10V. I thought the transistor was bad, but as I was fiddling with it, it suddenly started working. I think it may have been a bad connection in the patch cords or in the adjustment pot. Now it locks on solid as a rock.

They are really fond of using little light bulbs as current limiters on output stages. They try very hard to protect everything from what a user might do like patching an output to a power supply.

I'll have to decide what to move to next. I'll keep an eye on this reference supply to be sure it continues to work.