Steve -
Your PTO is on the way back. I finally got the time to pack and ship it. It's been sitting on the
bench, running for the last week or so with the counter on it. It stays within +/- 100 Hz from day
to day, just sitting in the open. I turned the counter so I could see it from my desk and would
just look up at it to check from time to time. When the AC kicks on, it moves a little more, but
that's not going to happen mounted inside the receiver! We had a couple of cool days when the AC
didn't kick on all day, and the frequency just sat there.
I checked it several times yesterday, and about the third time I looked up it dawned on me that it
hadn't moved a single Hz!! Hmmmmmm. Not likely. So I looked and the GATE light on the counter
wasn't flashing........ So I hit the reset and it went to 0?!?!? I touched the scope probe to it
and still full amplitude. So I switched the counter from low range to high range and back on the
counter and it started counting again..........
The 6AU6 is an ok sub in the PreMixer, but is only about 1/2 the Gm of the 6HS6. I think there is
plenty of gain, so probably no big deal, but possibly less LO output, degrading performance. The
6AH6 is a much better choice for a reasonably priced sub, with even higher Gm.
It's not a problem in the R-4A, but the 'HS and 'AH are 0.45A filament, vs 0.3A for the 'AU may be a
problem in a series arrangement.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Steve Wedge wrote:
I know the 6HS6 and 6AU6 have the same base and are actually listed as substitutes for each
other. I also know the 6HS6 has higher Gm.
I noticed, when putting this R-4B back together, that the PO put a 6AU6 in V8. The receiver seems
to work fine, so how critical is it using a 6AU6 in V8 (the premixer)?
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