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]> wrote: > > Garey Barrell <[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> > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > ---------------------------------------------------------------------- > > Submissions: [EMAIL PROTECTED] > > <mailto:[EMAIL PROTECTED]> > > Unsubscribe: [EMAIL PROTECTED] > > <mailto:[EMAIL PROTECTED]> - unsubscribe drakelist in body > > Hopelessly Lost: [EMAIL PROTECTED] > > <mailto:[EMAIL PROTECTED]> - help in body of message > > Zerobeat Web Page: www.zerobeat.net <http://www.zerobeat.net> - > > sponsored by www.tlchost.net <http://www.tlchost.net> > > > ---------------------------------------------------------------------- > > > > > > ------------------------------------------------------------------------ > > > > No virus found in this incoming message. > > Checked by AVG Free Edition. > > Version: 7.5.516 / Virus Database: 269.20.7/1283 - Release Date: > 2/16/2008 2:16 PM > > > > > ---------------------------------------------------------------------- > Submissions: [EMAIL PROTECTED] > Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body > Hopelessly Lost: [EMAIL PROTECTED] - help in body of message > Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net > ---------------------------------------------------------------------- >
