All,
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I have a very early (S/N 260) Drake 2-C on the bench with an AVC issue I need a head check for.? The symptom is that the idling AVC voltage, which should be adjustable during alignment to -1.35V will only adjust around the -0.4V to -0.6V range.? Troubleshooting has revealed that the negative voltage supplied to the circuit is lower than expected -- it's riding around -25V, instead of an expected -70V (although some schematics show a -50V).? I've traced this back to the power supply and confirmed that, at the junction of C53 and D5, the voltage is indeed about 25V.
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Does anyone know if, in the very early versions of the 2-C, the AVC voltage was significantly lower, or is there likely an issue that needs to be further diagnosed?
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What started all this was that while the slow AVC works fine, if you select fast AVC with the RF gain wide open, the AVC rapidly oscillates unless you back the gain down.? Voltage checks have led me down this path, but I don't want to jump to conclusions due to the extremely low serial number involved.
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73 - Steve, KW4H
