Troubleshooting guide

Cinematronics Vector Monitor Repair Guide v.1.0
Page 32 of 53
4. Output of each TL081 (pin 6)
You can see the output from each stage as the signal goes through and you can usually spot which
stage has a bad component in it this way. Make certain you have disconnected the yoke when you
check the signal path. If you try running the monitor with the yoke connected and the chassis
mounted output transistors plugged in, you will blow something.
Begin troubleshooting with Q104/204 (2N5322), as these are the most likely failures. If one
channel is working, test Q104 against Q204 using an analog meter in “ohms/resistance” setting.
Test all 6 combinations of the 3 legs and make sure both transistors “look” the same on the meter
deflections. If not, remove it and retest out of circuit (should have some resistance in 2
combinations and infinite in the other 4). If it tests badly out of circuit, replace it. If it tests OK out
of circuit, check adjacent transistors in the same manner until you find the all the ones which are
bad and make the non-working channel’s transistors all mimic the deflections of the working
channel’s transistors. You will find that about 80% of the bad transistors are shorted and about 20%
are open.
Next, start by looking at the output of the DAC 80s, and then follow the waveform through the
LF13331 and so forth. Check to see where the signal starts looking bad (i.e., chopped off to only
the top/bottom/left/right half).
To further isolate the problem in your monitor, you can cross the horizontal and vertical stages
between the control and power sides. Notice those two long jumper wires going from the area with
the pots, over to the power amp sections? Those carry the final deflection signals to the amps. By
crossing them, you turn the display 90 degrees, and you can isolate the problem to either the
control or power sections.