Technics px keyboard power supply issue

[tonepumpamps]

I'm working on a Technics px keyboard that seems to have a power supply issue I can't trace down.
When the keyboard is powered up there is a loud hum even with the volume turned down.
After checking out the power supply I have no -15Volts.
There isn't any input voltage to the regulator. When I removed the regulator I got -20 volts at the input of the regulator (I have -28V at the input of the other ic's)
Something is pulling down the -15V and I'm having a hard time finding it.
Anybody have any suggestions?

[Enzo]

I suggest first check the series resistor at the input, the 6.8 ohm R57. See if it has gone way high in value or opened.

The regulator itself, IC2 could certainly be bad. And there is a cap and zener across its output, a quick check to see if they are shorted.

And other than the few op-amps on the power supply/amplifier board, the rest of the circuits that use -15 are off the board, so you could unplug the cable at CN1 to the main board to see if something over there is loading you down.