Hi Jordan, Good work testing and documenting your problem. Glad the 1 MOhm isolation res worked out. It looks like the 1st var IF is the key to this problem. I'd focus on fixing the tracking and examine the 3 tuning cans - take them all out and apart and examine them. Make sure that the 3 trimmers peak correctly. I've had numerous problems with the 5 SM caps in the 1st mixer plate circuit. Also check bypass C280.
Regards, Larry On Sun, Apr 14, 2024 at 7:28 AM Jordan Arndt <[email protected]> wrote: > Hi Bob... > > Yes, I have an Ailtech 460 sig-gen, and yes, none of the bands are totally > dead. > > To check the sensitivity, I use the sig-gen at 50uV and again at 1uV, in > AM > mode with 400hz modulated at 30%. I also use the Carrier Level meter > and/or > the Line Level meter accordingly. > I also check to see if I can peak the internal tube noise by adjusting the > Ant Trim and checking for a peak in the noise as indicated on the Line > Level > meter with the receiver input terminated in a 50 ohm load. > > Wth a 50uV input signal, the Carrier Meter shows a drop off below 8Mhz of > ~ > 4 to 6dB per band, with the 3 Mhz band being the outlier showing a ~ 12dB > drop which I believe is due to a weak crystal which produces only 2.4Vdc > at > E-402. The rest of the lower band crystals all meet the -4 to -11Vdc spec > as > measured at E-402. > > Aside from a minor tracking problem in one of the 1st variable IF > transformers, the rest of the RF xfrmrs appear to be working normally and > track properly. I do note some scratching when the Ant Trim is rotated > quickly, but that only appears with no antenna connected. The Ant Trim > peaks > normally on all bands. > > I hope this answers some of your questions... > > 73...Jordan VE6ZT > ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
