Kurzweil PC88 - Page 85

Chapter 4
10.
11.
12.
13.
Troubleshooting
If there is excessive heating of VR1, VR2 or VR3
with J302 removed, then replace VR1, VR2 and/or
VR3.
At VR4 (-5VANA) check the third pin from the
right for -5 Volts. Check the second pin from the
right for approximately -10 Volts. Repeat previous
test (filter cap for VR4 is C34).
If the reading on the second pin from the right is
zero or very low, the fault may lie within the
oscillator circuit comprising of U4, Q1, Q2 and/or
associated components.
Look for a sine wave on U4, Pin 1 and a half sine
wave on Q1 and Q2 base.
If everything measures correctly, reconnect J302
and check the output voltages at VR1, VR2, VR3
and VR4. If any line is found to be low, shut
power off and trace the excessive low to the
appropriate DC power line.
Refer to Schematic Diagrams. Trace power circuit.
Check for correct voltages in signal path.
Find and replace bad component(s).
If necessary, order circuit board replacement.
PC88 Service Manual
4-5