I dusted off the R4A that I retired maybe 3 years ago when i got an R4B, as
I recall it WAS working fine when I put it on the shelf, but I could be
wrong.
Signals seem plenty strong. but no BFO though signals seem plenty strong,
sounds like it's ALMOST oscillating.
It's the 11-tube mode, serial 6987G.
Other notes: My DVM is cheapo, so not high impedance. My scope is on the
fritz.
I run the Drakes off an autotransformer, so 110VAC not 120VAC.
I have Garey's new R4A CD.
Took base voltage readings (see below), plate on V5 and V12 were quite a bit
higher than they should be,
so I thought to myself, whoa, maybe an OA2 is in there instead of an OB2.
So, I took the OB2 from my R4B, but this didn't change my readings, but
actually, can't make out any markings on either of the tubes.
Now I'm worried both receivers had OA2 in there instead of OB2, but I find
it doubtful that both would be wrong, and the R4B has been working fine for
several years.
I have the voltage readings from when I worked on the AGC back in 2008, and
they were fine then.
V5 pin 1 s/b -1, was -18
pin 5 s/b 110, was 146
pin 6 s/b 70was 95
V8 - haven't been able to check that one yet, hard to get the probes in
there
V9 pin 1 s/b -1 was -21
pin 5 s/b 128 was 144
pin 6 s/b 110 was 120
V11 (OB2) - haven't been able to check that one yet, hard to get the probes
in there
V12 pin 1 s/b -44 was zero
pin 5 s/b 55 was 128
pin 6 s/b 55 was 128
Besides these voltage anomalies, what else might I check, maybe D11, D12 for
the BFO Q6 2N3394 ?
Chuck, K1OM
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