Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Chuck -
OK. That's good!
From your description, the AVC circuitry is working...
I don't have a good photo, but I bet three of the four components are on
the board with the S-Meter Sensitivity pot, next to the crystal. R40
(1k Trim), R41 (820), R89 (560) and associated connections. A series of
ohmmeter checks should find it. I'm betting R40 is open, or a broken
wire/connection. :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Chuck Grandgent wrote:
Thanks Garey,
well the meter seems OK, the DMM on lowest resistance range causes it
to deflect a tad. I had to repair the AVC switch at one point, I
guess I should check there, among other places.
Chuck, K1OM
On Feb 6, 2008 4:20 PM, Garey Barrell <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Garey Barrell <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
made an utterance to the drakelist gang
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Chuck -
The S-Meter is a simple bridge circuit that compares the plate current
of V2 and V3 with the plate current of V4 and V5. There are only two
resistors and two trim-pots! Since the radio seems to be working more
or less normally, those tubes are probably "good enough". If the
meter
needle is just sitting there on the mechanical zero point, it's most
likely an "open" in that circuitry. Just as a guess, I'd first check
the meter terminal connections, then wonder about the S-Meter
Sensitivity pot, but it could be a bad connection or (YIKES!) an open
meter movement. The movement itself is 3 mA, as are ALL the R-4/T-4
meters, so can be checked with a DMM for continuity. Don't try to
use a
VOM, as they put too much current through the ohmmeter circuit.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com <http://www.k4oah.com>>
Chuck Grandgent wrote:
> R4A, S-meter was working OK, just noticed it is not right now, don't
> know for quite how long.
>
> AVC is working, as evidenced by turning RF gain all the way down and
> then back up, AVC slow takes very noticeably longer for the RF
leve to
> return once I turn up RF gain, compared to AVC fast.
>
> Adjusting R40 and R42 for S-meter and balance have zero effect,
> S-meter is all the way to the left.
>
> Things to try ?
>
> Tnx, Chuck, K1OM
>
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