Star Tech Journal

10
EXIDY SERVICE NOTES
Wells-Gardner "Black" Leval Control
On Wells-Gardner monitors there is
black level control which is like a
brightness setting. Although not as
visible as the other set-up controls,
the black level control is used to
adjust a screen which is too dark or
too bright.
This control is set at the factory but a
minor adjustment may be necessary.
Black level control (VR201) is a 1.5 K
pot located on the interface board.
The voltage at this pot should be
adjusted to approximately 8.91 volts
DC and, as this control is very sensi-
tive, it doesn't take much movement
for large black level changes.
VR201
Power Supplies
One of the first areas to check when troubleshooting a game is to make sure you have correct voltages. Proper
voltages for the logic and audio PCB's are checked on the respective PCB board. The 5 volts should be checked
near the microprocessor while being adjusted on the power supply with the voltage adjustment pot. The voltage is
set when the power supply is under load (while it is connected to the logic board, for example).
It is possible to have the proper voltages but have an intermittent problem with a game because of the power
supply. The only way to really verify this type of problem would be to substitute a known good power supply for
the one in question. lntermittence in a power supply is usually caused by the externally mounted components
(diodes and regulators) not making proper contact with the regulator board. (See illustration). Reheat and resolder
these connections (especially power supplies with eyelets) to make sure a correct connection is made.
0
1,2,or3
external
components
0
CJ
0
0
resolder here
REPRINTED COURTESY OF EXIDY'S "ZERO DOWNTIME" TECHNICAL NEWSLETTER.