Re: 7704A Vertical Amplifier Issues

Albert Otten

I still wasn't very confident about my results and now did measurements in another 7704A. The A44 board is the later version and R4419 is 33R as should be. But guess what ... the voltages were as if Q20 etc. did not exists (Ve < Vb) and as if CR4419 just conducted.
50 mV across R4419 (in stead of earlier 125 mV across 39R) which is closer to what Barry found.
I appeared that R4420 (5k6 to +50V) was open, but without any sign of overheating. Luckily this does no harm and explains the results.


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