Actually it's 6987G.
And 22k across primary of T10, and no R142.
And you mention "R4B Version 1, s/n 7000+ has R146 (22k), R142 (4.7k)
in series, and C159 (0.01) bypass", so that explains the 22k resistor.
The C159 failure has been happening over time, to the point where when
I first turned it on, it would be quite dead, but usually it would
clear up. I thought it was dirty bandswitch contacts or something.
Then I noticed the S-meter not working, and it wasn't that along that
it did, but hard to remember.
What's that letter after the serial # ?
Chuck, K1OM
On Feb 17, 2008 10:06 AM, Garey Barrell <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Garey Barrell <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
made an utterance to the drakelist gang
----------------------------------------------------------------------
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 <http://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]>
> <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 -
>
> 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> <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]>>
> > <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 -
> >
> > 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> <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]>>>
> > > <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:
> > >
> > > 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]>>>
> > > <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 -
> > >
> > > 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>
> > <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]>>>>
> > > > <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]
<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]>>>>
> <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]
<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>
> > > <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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