Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Chuck -
Obviously you can't have 150VDC on one side of an 820 ohm, 1/2W resistor
and 5VDC on the other........
Measure the voltage at each node along the path from the +150 to Pin 5
of V5 and see where it's getting lost. Perhaps bad solder joint? Or
open primary on T10?
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Chuck Grandgent wrote:
The plot thickens.
I checked resistance and voltage at all the pins for V2, V3, V4, V5.
The two bads are:
1) V5 12BA6 pin 5 (plate), resistance is 150 ohms, s/b 10k. And
votage is 3 volts, s/b 110v
I guess R41 and maybe R142 bear more checking, though if either of
these went high, I can't account for the low plate to ground
resistance through this fault.
Swapped this tube also with no effect.
2) V2 6HS6, manual says pin 3 (filament) s/b 6.3, is zero and pin 4
(filament) s/b 12.6, is 6.4. Looking at the schematic, not sure what
to make of that. And actually I did swap between my two 6HS6's with
no difference.
Chuck, K1OM
On Feb 10, 2008 6:54 PM, Chuck Grandgent <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
OK, got some time to spend on this today.
R40, R41, R42, and R89 SEEMED to checkout OK.
However, if I put a potentiometer across R41 and adjust it for a
low value, I can get the S-meter to respond. Then, the S-meter
zero adjustment R42 can bring the S-meter to any level on the meter.
But, it seems totally non-responsive to any received signal.
I was also able to adjust the receiver sensitivity potentiometer
on the bottom so TP2 was minus 1.35 volts.
I replaced V4, V5, and V3, with no discernable difference. I
didn't have a spare for V2 6HS6.
What to check now ?
Thanks, Chuck, K1OM
On Feb 6, 2008 5:12 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 -
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 <http://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]>
> <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>>
wrote:
>
>
> Garey Barrell <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]> <mailto:[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>
<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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