Excellent suggestions, all. I'm going to print them all out and go through it methodically. I do have a URM-25D in good calibration. So I'll make some notes as I go along, and note its performance before I muck with it.
I do feel a bit foolish, when I got home and unpacked it and powered it up, I guess band conditions were very good, a bit quieter on the bands this morning :) Thanks to all, Chuck, K1OM On Sat, Apr 18, 2009 at 10:11 AM, Garey Barrell <k4...@mindspring.com>wrote: > Chuck - > > Depending upon the s/n of your R-4A, the two receivers are almost > identical, electrically. So there is a reason for the apparent difference! > > 1. Check the voltage, with a HIGH-Z meter, (not a cheapy DMM,) at TP-2. > On top of the chassis, under the Passband Tuner shaft. Should be -1.35 > VDC, and this sets the sensitivity of the receiver. If you have done AGC > work, you probably know this, but ... > > 2. Check that the S-Meter ZERO is correct, and that the meter reads 60 dB > over S9, (full scale,) with the RF GAIN at full CCW. > > 3. Most likely weak tubes are V4 and V5, since this is where most of the > receiver gain is. > > Finally, one of the "problems" with the Drake receivers is their excellent > AGC system. The basic system is so good, that ALL signals seem to be at > about the same level in the speaker, and you have only the S-Meter to tell > you which are the strong ones and which are the weak ones. > > Really the only way to compare the receivers is with a calibrated signal > generator. I really like the little XG-1/2 by Elecraft or the S9 by > NORCAL. Both give you a known 1 uV signal ( ~S1-2) and a known 50 uV signal > (S-9) at various frequencies. You just have to tie a long piece of yarn or > something to them to keep from losing them on the bench! > > You can do a touch-up alignment in about ten minutes, using the Calibrator > and the S-Meter. Typically the transformers do NOT need adjustment, and a > simple peaking of the trimmers for the RF, MIXER and PREMIXER stages are all > that is needed. > > 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: > >> Well the purpose of this post is twofold: >> >> First, despite periodic negative reports about the eB** place, I wanted to >> report my just received acquisition of a very nice R4B. Decent price, >> decent shipping charge, very well packed, nicely bound copy of the R4B >> manual plus misc other relevant R4x articles, received approx three days >> from the end of the bidding (USPS Priority). I don't recognize the call from >> being on this list, so I won't identify unless there's a reason to. In >> short, I couldn't be more pleased. >> >> The second reason for the post is about my R4A, and the diff between it >> and he R4B. >> I have to say, I have been happy with the R4A over the appro 10 years I >> have owned it. I have had to do a fair amount of work on it in the AGC >> section, but I have done lots of great QSO's with it. And to be fair, it >> lives in my garage, here in No. Florida, and what with the heat, humidity, >> and insects, it has not had an easy life. >> >> Anyway, my first impressioin on powering up the R4B is, that it is SO MUCH >> MORE SENSITIVE than my R4A, including the S-meter response. Nevermind that >> the switches seem a lot cleaner, the tuning knob spins easier, etc.. >> >> So anyway, I wanted to ask, where would you first begin to look in the R4A >> to account for the difference in sensitivity between it and the R4B I just >> got ? I have checked all tube pin voltages, and they do agree closely with >> what they should be, and I believe the tubes are OK. >> >> Chuck, K1OM, Alachua, FL >> >> >> > _______________________________________________ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist >
_______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
