Any Swan gurus here. 500C problem - BoatAnchors Forum at eHam.net

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eHam.net Forum : BoatAnchors : Any Swan gurus here. 500C problem

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Any Swan gurus here. 500C problem	Reply
by K4TLJ on October 25, 2009	Mail this to a friend!
I am refurbishing a 500C transceiver. All is good except... Drift during warm-up is about normal for a Swan and seems to stabilize after 30 minutes. When the mike is keyed the frequency is stable. That is, it stays the same as when in receive mode. But when returned to receive mode the frequency jumps anywhere from 10 hz to 500 hz. Usually it stays at the new frequency but sometimes drifts back almost to the original frequency. I have checked resistors and replaced anything that resembles a paper cap or electrolytic. I have re-torqued every screw that is accessible. All diodes have been replaced. The -10v is actually -9.523 and only changes a few millivolts when switching from receive mode to transmit mode and there are no transients as verified with the scope. BTW, I am monitoring the frequency with a AADE digital dial. The frequency shifts whether the digital dial is connected or not. I can verify that with a frequency meter and by the audible difference in received audio. Any suggestions appreciated.

RE: Any Swan gurus here. 500C problem	Reply
by K4TLJ on October 26, 2009	Mail this to a friend!
OK here is the scoop. I was so confident that the relay was at fault that I ordered one before going to all the trouble of accessing the relay to inspect and clean it. I had already cleaned all the band switches and caps with the naptha and oleic acid cleaner I bought from Bill Turner. I use it on my vintage radio restorations with no problem and it seemed to work fine. However, I had been conservative and used the cleaner sparingly, just enough to wet the contacts. I decided to clean all of the contacts again with some CRC QD Electronic Cleaner from the auto parts store. I first cleaned the bandswitches under the chassis. No change. Then I cleaned the bandswitch inside the VFO. No change. I then cleaned the VFO tuning cap. Better. I cleaned the cap again this time really concentrating on the finger contacts on each end of the shaft and turning the dial back and forth. I really flooded the tuning cap and then inverted the radio and allowed it to dry for an hour. The drift in now minimal and the frequency jumping is gone. Steady as a rock.

RE: Any Swan gurus here. 500C problem	Reply
by KE4DRN on October 27, 2009	Mail this to a friend!
hi Terry, good fix ! take a look at DeOxit brand contact cleaner, many of us use it on our older kenwood hybrids, makes them work like new again. the carrier fluid from the cleaners can be absorbed by the wafers in the stacked switches, the end result is a damaged wafer. http://www.mcmelectronics.com/product/200-070 DeOxit brand by Caig Labs, works great. Yes, it is expensive but you only need to use the smallest drop. 73 james

RE: Any Swan gurus here. 500C problem	Reply
by KG6YV on October 28, 2009	Mail this to a friend!
IN fact to go further on Caig De-OXit, Antique Electronics in Tempe ariz carries all the variants. IT comes in 5% spray cans which is good for most cases all the way up to a small dropper bottle of 100%. www.tubesandmore.com is their website. 5% or 10% de-oxit (red can) is probably good enough for most jobs, including BFO tuning cap ground clips. Greg KG6YV

RE: Any Swan gurus here. 500C problem	Reply
by K4TLJ on November 1, 2009	Mail this to a friend!
Well the problem came back... more than once. This last time I resoldered all the connections to the bandwitch and tuning cap. I also loosened and retightened the mounting bolts for the VFO board. So far so good. Only time will tell.

RE: Any Swan gurus here. 500C problem	Reply
by K4TLJ on November 16, 2009	Mail this to a friend!
Well here is the latest 'fix'. I thought it was fixed several times. The trouble would go away for days then come back same as always.. frequency jumping up to 500 Hz when the PTT was dropped. Today the problem came on and I carefully jumpered the VFO accessory jack connections for the VFO voltage and output signal. The problem continued. I removed the accessory dummy plug and problem went away. Replaced and problem came back... ah HA! I figure a very high impedance leak within the plug. I cleaned the plug thoroughly with soap and water scrubbing well with a vegetable brush and rinsed with distilled water. Put everything back to original and problem is not there. I also bypassed all voltage leads to the accessory socket with .01uF 1KV ceramic caps to ground. Not sure this did anything but can't hurt either. The trouble had gone away earlier after removing and replacing the VFO board mounting screws. There was a white corrosion there. All possible connections inside the VFO were cleaned and then cleaned again. The VFO is VERY stable and drift is minimal after a 15 minute warm-up so at least I did some good. If it has not failed in a month I will call it fixed.

RE: Any Swan gurus here. 500C problem	Reply
by KC2SXZ on November 25, 2009	Mail this to a friend!
HI; MY NAME IS HARRY KC2SXZ. I HAVE A SWAN 500, THAT WORKS WELL, EXCEPT FOR THE DRIFTING. IT DOESN'T DRIFT MUCH, BUT IT IS NOTICABLE BY OPERATORS THAT I TALK TO. I FOUND OUT THAT THERE IS A VFO STABILIZER MADE THAT YOU CAN USE TO ELIMINATE THE DRIFTING. IT IS CALLED A DPK VFO0 STABILIZER, AND COSTS $70.00 TO PURCHASE. YOU CAN E-MAIL k4dpk@comcast.net,TO GET INFORMATION ABOUT IT. I HAVEN'T BAUGHT ONE YET, DUE TO BEING A HANDY CAP, ON A FIXED INCOME, AND I HAVE A IC-706 TO USE AS THE MAIN RIG. I WAS TOLD THAT HTAT STABILIZER WORKS WELL. ALSO WHILE AT IT, I AM LOOKING FOR A CHEAP FREQUENCY COUNTER FOR MY SWAN, IF ANY ONE HAS ONE THAT HAS ONE THAT THEY ARE WILLING TO PART WITH. GOOD LUCK, AND LET ME KINOW AT englejr8@verizon.net, IF THAT STABILIZER WORKS. WITH DUE RESPECT HARRY KC2SXZ

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