Well, since I couldn't make out the markings on the VR tube in both my R4A and R4B, I just drove over to vacuumtubes.net (next town over) and got a couple 0B2's, these with clear markings.
But, voltages in my R4A are still high, just as described below. So anyway, they weren't 0A2's in there, they were the correct 0B2. Chuck, K1OM On Sat, Dec 18, 2010 at 6:40 PM, Chuck Grandgent <[email protected]> wrote: > 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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