Burt, Thanks for the information. I thought that the tolerance was supposed to 100 Hz, as You said. As far as I know, this is the original crystal that came with the rig when NMSU bought it. I will spend more time working with the rig this weekend.
I am looking for a solid state LPB transmitter, if you are interested in selling yours. I have just worked out a trade to another Amateur for a carrier current line coupler. Joe Gray W5JG On Fri, Jun 21, 2013 at 11:47 PM, Burt I. Weiner <b...@att.net> wrote: > Joe, > > As was mentioned earlier, U.S. AM broadcast tolerance is +/- 20 Hz. Many > of the LPB low power transmitter were used for TIS/HAR service. The > tolerance for that service is +/- 100 Hz. I've maintained several of these > stations, including the 100 watt system on 530 kHz at LAX Airport. The > transmitters were made by LPB, were all solid state, and stayed within 5 Hz > for years without any adjustment. It's been a real long time since I > worked on any of the tube version of these, but >200 Hz sounds like > something has gone wrong. It may be a defective crystal or some component > in the oscillator circuit. To your knowledge, is the crystal that's off > frequency a LPB supplied crystal? The LPB's were also used for broadcast > transmitters, particularly at daytime stations that had very low power > nighttime authorization. Used that way they had to maintain their > frequency within the +/- 20 Hz tolerance, which was never a problem with a > good crystal. They are actually pretty good transmitters and are capable > of 125% positive peak while keeping the negative peaks at 95% or less when > driven with a real audio processor. I have one of the 30 watt solid state > transmitters and one exciter board. I also have one that is an amplifier > only that I'm able to drive to about 15 watts out with my bridge generator. > > LPB went out of business a few years ago and left a lot of customers who > had pre-paid for their equipment holding the bag. I was one of them. It's > a shame because they really are good transmitters. > > Burt, K6OQK > > At 09:26 PM 6/21/2013, time-nuts-requ...@febo.com wrote > >> >> I have an old AM transmitter that has three 6AL11 compactrons. The >> crystal >> >> is a fundamental, cut for 660 KHz. I don't have a schematic for this >> thing, >> >> but I believe that one half of one 6AL11 is used for the oscillator. >> >> >> >> The problem is, the frequency decreases as the rig warms up. It will >> >> eventually stabilize, but the final frequency is over 200 Hz low. Not >> as >> >> good as it should be. I think the original specification was well under >> >> half of that. >> >> >> >> I have replaced the electrolytic caps. The others are mostly >> silver/mica >> >> with a few ceramics. I checked all of the resistors and only found one >> that >> >> was out of tolerance (I replaced it).Three NOS tubes were installed. >> There >> >> are no tunable components in the oscillator section. Only the output >> >> section has anything tunable. >> >> >> >> I know that there are many Amateurs on the list and I'm sure many know >> more >> >> about old tube rigs than I do. Does anyone have a suggestion as to >> what the >> >> trouble might be? >> >> >> >> Joe Gray >> >> W5JG >> > > Burt I. Weiner Associates > Broadcast Technical Services > Glendale, California U.S.A. > b...@att.net > www.biwa.cc > K6OQK > ______________________________**_________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.