[R-390] R388 AVC Question

[g4gjl at btopenworld.com]

I am working on my recently acquired R-388, which is in superb condition. *Thank you* (you know who you are!)


Unfortunately this receiver has the distortion problem associated with the AVC circuitry, often reported on these receivers. At lower AM signal levels, or with the RF gain backed off with SSB, the audio quality is fine.


The receiver distorts badly on strong stations, and appears to have  limited AVC action. The signal meter never makes it above approx. 50dB on the scale, even on the strongest of local AM broadcast stations.


I have measured the -53v point (-48), -56v point (-56.3) and the -44 v point (-44.1). I now suspect C205B as being leaky, but hav not had time yet to check it out. Also there might bea  low gain in V111, again, not checked out yet, but the -44v would indicate less likely. (measured values in brackets)


I have changed C204 (a frequently reported culprit) to a low loss polystyrene type and checked the 0.01uF ceramics on the AVC line (no leakage to speak of).

So should I be diredcting my attention to any other components before I start pulling out the tube tester to look for H/K shorts?

Pete
G4GJL