I was given a Pianocorder system that I am installing in a small spinet
piano.  I am only using the solenoids, 3 driver boards, and the power
supply.  The cassette tape recorder and the 2 large logic boards are
replaced with 1 special board that converts the Z-tronics pipe organ
data into signals needed for the Pianocorder driver boards.

Since I don't know the condition of these Pianocorder boards, I want
to bench test the components and bring up the system slowly.  I found
multiple problems with bad solder joints on the driver boards.  These
are single sided boards, which tend to have this problem.  I have this
under control for now.

My first step is testing the power supply.  The +160 and +12 volt
systems are very simple and I understand them.  My problem is the +5
volt power supply.  Does anyone know where I can get a schematic for
this beast?  It is labeled as a Level A Superscope ASSY No.100-04D016
2600.  I must say that it makes me nervous debugging this power supply
since it doesn't have any isolation from the 117 VAC line voltage.
If you don't know what you are doing or you slip with the probe, there
could be big problems, such as electrocution or smoke!

When I turn on the power supply without any loads, the +5 volt line
jumps up to +16 volts.  Do I need to connect a load to the output to
drag the output down into regulation?  The external 5-volt series pass
transistors don't seem to be shorted together.   In looking at how the
regulator chip (RCA CA723) is connected in the circuit, it just doesn't
make sense.  There seems to be a voltage doubler circuit that supplies
32 volts to the regulator for some unknown reason.

Can anyone help me?

Pete Knobloch
Tempe, AZ