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]> wrote: > > Garey Barrell <[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> > > > > 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 > > > ---------------------------------------------------------------------- > > 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 > > > > > > > > > ---------------------------------------------------------------------- > 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 > ---------------------------------------------------------------------- >
