Troubleshooting guide

Cinematronics Vector Monitor Repair Guide v.1.0
Page 38 of 53
• Check resistors R116, R216.
An example. If the picture would start out OK, but after a few minutes the Y heat sink would get
super hot and this would cause the weaker of the two TO-3 transistors to fail, which then caused a
loss of -Y deflection followed shortly thereafter by both breakers tripping.
Feel the heat sinks. If either deflection heat sink is too hot to touch then suspect that the cluster of 5
diodes (D107-D111) in the center of the monitor PCB has at least 1 bad diode. They are type
1N4003 and are VERY inexpensive so rather than figure out which one is bad, just replace all five
and upgrade them to 1N4004s. When I had this problem, the Freeze spray narrowed the bad part to
those diodes and now everything runs cool and steady.
Symptom: Narrow Line on Display.
• Check Analog Switch IC1.
• Check Q110, Q210, Q111, and Q211 with ohmmeter or transistor tester. Inspect solder
connections on circuit board molex connector socket pins.
• Verify continuity between display board and heat sunk power transistors Q110, Q210, Q111
and Q211.
• Check for bad solder & crimp connections to yoke wires.
• Check for open yoke windings with ohmmeter.
Symptom: No Hi-Intensity Vectors.
If you can see vectors but the intensity is too low, that means the oscillator section of the Hi-V
circuit is probably working and the 16kV is being generated. The 90V is simply the half-wave
rectified and filtered output of a separate secondary winding on the XFMR. Check the filter cap
C17 (10/100V if I’m reading the schematic right) and the diode CR6 (MR818). Also pull and check
the two intensity control transistors, Q1 and Q3. I would try pulling these transistors, and then
powering up the monitor to check the +90V again, pulling the transistors removes the load from the
+90V supply. Unless the transformer toast you should be able to get this fixed.
Well, you can safely short the emitter-collector of the transistors in that circuit to see if they are the
problem. The transistors are forming a switch function here so shorting the emitter to collector is
just doing the same thing (albeit a continuous instead of controlled action) you should see the
screen come on full strength for the beams, with no blanking (rather busy picture) but at least you
will know that the tube is emitting, and that the electron gun is OK. Next, a logic probe on the
outputs of the 7406 should indicate if signal is getting through. You should have about +96VDC on
the pot. That is its bias voltage. Turn the pot so that the wiper is set fully clockwise and short the
wiper to ground momentarily, you should see the screen light up with the game lines. Next, check
the SPOT KILL circuitry. It may be active (Low) and killing the screen drive transistor.