We are starting to work at a new client’s studios. It is a bit like stepping into a 1980s time machine, as the newest console seems to be the Broadcast Audio console in the FM studio. I feel I should wear a wide colorful tie and part my hair in the middle when working there. There is also an older UMC console in the second production room.
A what?
Exactly.
It seems the UMC console (UMC was a Connecticut-based console manufacturer that was later sold to Broadcast Audio) was having an intermittent hum problem on all the audio buses.
After poking around under the hood for a few minutes, I decided I should begin with the basics. Checking the power supply for ripple seemed like as good a place to start as any. This console has a 30-volt and a 12-volt power supply. The 30-volt supply checked out good, but the 12-volt supply, not so much:
2.7 volts AC on the 12-volt DC power supply. That will put some hum on the audio, all right. I tried to replace the power supply main filter capacitor, but it had no effect. The regulator must also be bad and it is a Motorola part number which is likely not made anymore.
This is a pretty standard off the shelf power supply, I should be able to get one from Mouser for about $60.00 or so for a linear unit, which will be cheaper than us trying to trouble shoot and repair the old one. In the meantime, I took the 10 amp 0-30 volt bench supply and pressed it into temporary service. The console is working again, for now.
At some point, all this old, um, stuff needs to be replaced.