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With an oscilloscope, meter and frequency counter I started to look at my VA62
outputs in detail.
The audio output was distorted and had hum, in fact most of the drive outputs had too much hum. The 3.58MHz output from the separate front jack was distorted and noisy. The 30Hz (VCR servo) front panel output wasn't working either. The programmable 30-50MHz IF output was off frequency and drifting.
One handy thing was that the RF/IF switch modification allowed a higher output than usual for the RF output, that allowed my frequency counter to work.
Troubleshooting one output at a time I worked through the problems.
After replacing the op-amp IC that was used to generate the audio tones (no change), I discovered that someone had maxed out the oscillator signal levels. This caused the outputs to clip. Someone had worked on the unit that didn't know what they were doing, I was going to have to check every adjustment on the sections that were giving me problems.
Next I looked at the drive board. I found evidence that a lot of work had been done. There were signs that spots on the board had overheated and some part replacements were suspicious. I ended up replacing all the electrolytic caps, a couple of resistors, two zeners and a transistor.
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