August 1992
STAR* TECH Journal
Prince's Corner
Donald B. Prince
D&RMusic
Bozeman, Montana
WELLS GARDNER
79XX. SERIES
BLACK MONITOR PLAGUE
No PIX
Just recently I've come across five
or six monitors with the same
symptom and fix. All the moni-
tors had the dreaded "Black
Monitor Plague", in other words:
No picture, No raster.
POSSIBLE SOLUTION
This is sometimes caused by a
bad electrolytic capacitor@ C57
(47mfd@ 160V) but, sometimes
not.
CHECK
What I've found out is that R89
has a cold colder joint from excess
heating of R89 (not out of the
ordinary for a tight cabinet) or
R89 has broken away from the
pad or trace on the flip side of the
circuit.
This breakage is sometimes de-
ceiving. It looks ok at first glance
but upon closer examination with
a magnifying light glass, you can
see the break around the pad of
R89.
All the monitors
had the dreaded
"Black Monitor
Plague/✓,
in other
words: No picture,
No raster.
Checking with an ohmmeter is
also deceiving because the pres-
sure from your meter probes can
"make" the circuit.
If fact, sometimes this problem
manifests itself by way of an in-
termittent black screen, most of
the time in a location that turns
their games on/off at night and in
the morning.
THE CURE
The fix is simple enough, just
wrap a wire around the leg ofR89
and "electrically" reattach to the
circuit with solder. I say "electri-
cally " reattach because the cir-
cuit goes to many points, make
sure they ohm out.
Until next month. Happy hunt-
ing.