Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Chuck -
Great! That's very interesting that your VERY late serial number of
6987, which would make it one of the very last R-4As made, (the R-4B
started at 7000,) would not match any of the Version schematics.
Version 1, s/n 2007+ has R97 (33k) across the primary of T10, R26 (4.7k)
in series, and C74 (0.01) bypass.
Version 2, s/n 3040+ has the same
Version 3, s/n 4054+ has ONLY C154 (0.1) bypass
Version 4, s/n 5400+ has xxx , R142 (4.7k) in series, and C159
(0.01) bypass
Looks like Drake never did figure out just what to do with that circuit!
The first R-4B had
Version 1, s/n 7000+ has R146 (22k), R142 (4.7k) in series, and C159
(0.01) bypass
and stayed that way through the remaining two versions of R-4B
production. I'm wondering if they came to the conclusion that in
addition to improving the filter "blow-by" the 4.7k resistor would also
protect transformer T10 in case of a plate-suppressor short in V5, a not
uncommon occurrence with those tubes. Might not be a bad idea to add it.
Yes, I imagine it IS a bit hotter receiver with the 2nd IF Amp actually
amplifying instead of just being a coupling capacitor! A testament to
the AVC circuit of these receivers.....
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:
WaHoo !
That was it, C159 was way leaky, and my version does not have R142, so
that added some confusion.
S-meter's working great and receiver's hotter than I can recall in
recent memory !
As always, thanks Garey,
Chuck, K1OM
On Feb 16, 2008 11:13 AM, Garey Barrell <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Garey Barrell <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
made an utterance to the drakelist gang
----------------------------------------------------------------------
Chuck -
I was just typing my last as you were sending yours... Great minds,
etc. :-)
Nothing like having the right schematic..... C159 is a 0.01 disc
ceramic in this version.
R142 likely has gone way up in value or cracked. Not in the earlier
schematic I was looking at.
Schematic in separate message off reflector.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com <http://www.k4oah.com>>
Chuck Grandgent wrote:
> C159 was definitely bad Garey, replaced that and now I have S-meter
> action.
> However I still have no plate voltage on V5, and for the life of
me I
> can't see how it's wired for it. It seems to have a 22k resistor
> across T10 on the V5 plate side, and other than that and the
> connection to C159, I don't see how it gets to any voltage, it's
like
> R142 is missing.
>
> My serial number is 6987.
>
> Chuck, K1OM
>
> On Feb 15, 2008 11:30 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
>
----------------------------------------------------------------------
> Chuck -
>
> C159 may be very leaky or shorted. 0.1 uF at 200V. You
may have a
> fault in T10. B+ is applied to V5 through the primary of
T10 and one
> end of the secondary is at ground. Check DC voltages on either
> side of
> T10. A plate-suppressor grid short in V5 could have smoked T10,
> so use
> a known good tube.
>
> The 6HS6 filament is just a filament wiring anomaly. According
> to s/n
> 4054 schematic Pin 4 should be 6.3 and Pin 3 should be 0.
What is the
> s/n of your R-4A? I have the correct schematic.
>
> 73, Garey - K4OAH
> Glen Allen, VA
>
> Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
> <www.k4oah.com <http://www.k4oah.com> <http://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]>
<mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
> > <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>
> <mailto:[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]>
> <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
> > <mailto:[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]>>
> > <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>
> <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>>>> made an utterance to the
> > drakelist gang
> >
>
----------------------------------------------------------------------
> > 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>
<http://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]>>
> > <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>>>
> > > <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>
> <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
<mailto:[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]>>
> > <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>
> <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>>
<mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
> <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
> > <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>
> <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>>>>
> > > made an utterance to the drakelist gang
> > >
> >
>
----------------------------------------------------------------------
> > > 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>
> <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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