Check the outputs of all of the voltage regulators. The op-amps at the video outputs use + and - 15 volts, and if one of them isn't up to snuff, it'll make the video signals look wacky.
There are four voltage regulators: U101, a 7915, which puts out -15 volts.
U102 is a 7805 and it puts out +5 volts for the DACs (pin 14 on the AD561 chips)
U103 is a 7812, which puts out + 12 volts.
U104 is a 7815, which puts out +15 volts.
Note that both the 7815 and the 7915 regulators have resistor and zener-diode combinations at their outputs, which are used to generate + and - 8.2 volts. These voltages help control the video outputs, too. Measure the voltages across diodes D109 and D110. You should read about 8 volts across each one.
HTH,
Matt J. McCullar
Arlington, TX
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Received on Fri Oct 6 16:31:50 2000
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