Troubleshooting guide
Cinematronics Vector Monitor Repair Guide v.1.0
Page 37 of 53
unplug the yoke, leaving the HORZ and VERT transistors plugged in, and use a light bulb as a load
to determine what axis are blowing breakers.
Symptom: No Picture. CCPU board is known good. Power Supply tests good.
First, check for visibly damaged components. Replace as necessary. Listen for audible “clatter”
from the deflection yoke on the CRT neck. If the clatter is present, deflection circuitry is working
and the problem is in the intensity circuit. If there is no “clatter”, start by examining the DAC and
then deflection sections. Also check for a bad 7400 series inverter, IC7, which should be socketed.
Symptom: No picture. RF Chokes are Fried.
The RF Chokes are 0.18 ohm, 2W NON-INDUCTIVE power resistors and are on the monitor
board between the output transistor emitters and the deflection yoke. The RF chokes are in series
with the final stage power transistors. They are current sensing resistors that form part of the
feedback network going back to the output pre-driver.
If these smoked, chances are that your deflection transistors shorted. Check the transistors after you
replace the RF Chokes. Make sure you replace the chokes (and the resistor from the other side of
the yoke to ground) with NON-INDUCTIVE power resistors (i.e., not wire-wound)!
Symptom: No Picture.
Check the several 3-pin regulators that supply the various voltages on the monitor PCB. These go
bad frequently so check each one for proper output DC voltage at the 3
rd
pin. You might get some
indication of a problem with these by looking at the neon lamps clustered around the center of the
board a little off to the right. They are normally supposed to be off; if any is on, it indicates an
overvoltage condition. If your low voltages are OK, check your HV.
Symptom: Half a Picture.
Left Half [is present]: Check Q206, 208, 210
Right Half [is present]: Check Q207, 209, 211
Top Half [is present]: Check Q107, 109, 111
Left Half [is present]: Check Q106, 108, 110
• Check solder connections on heat sink molex plugs J3 & J4.
• Check diodes CR109, 110, 111
• Check diodes CR209, 210, 211
• Check transistors Q105, Q205