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Title: Band Switch Cleaner Post by: Steve W8TOW on January 22, 2014, 10:46:42 AM Hi all,
In an effort to resolve some receiver stability problems, I isolated the issue to the band switches...(2-3 different receivers)... Using liberal amounts of any kind of cleaner is not advised on such switches, so my approach is much more effective (usually)...I apply a small amount of DeOxit to a cotton swab or VCR Head swab (made from chamois cloth) and clean off the switch... Well, this isn't working out...In all of the rx, I am still finding some instability (oscillator stage) when I wiggle the Band Switch... If I am tuned to a fixed signal, switching up the bands and down the bands one might find the test signal 1 kc from where it was before! ALSO, I find without touching the receivers in any way, the test signal might "jump" randomly, +/- 0.5 kc Not something I like on CW.... SO, thinking that first the B.S. on a rig needs to be most stable, mechanically, I speculate that the cleaner is introducing some capacitance to the circuits... If this is true, what is better than DeOxit to clean a band switch??? (The rx in question are sx100, sx101 and gpr90....pretty random problem)! 73 Steve w8tow Title: Re: Band Switch Cleaner Post by: KA0HCP on January 22, 2014, 11:24:19 AM Having lost one reply, in short.
No. Unlikely to cause oscillator jumping in a low current reciever circuit. If saturation of switch materials phenolic or ceramic is suspected, use standard cleaning soapy wash, copious rinse, apply non conductive lubed contact cleaner. Check switch for contact tension, loose or corroded rivets, hidden wire breaks under insulation possibly due to solder wicking. Cold solder joints. Good luck, and get out the magnifiers! bill p.s. I would also concentrate effort looking at good grounds in the oscillator circuit, wiper contacts. Loosen, clean, reseat capacitor frames. Title: Re: Band Switch Cleaner Post by: w3jn on January 22, 2014, 05:04:16 PM Clean the wipers of the osc section of the variable capacitors and make sure the end bearing is adjusted properly. Best to remove the end bearing, clean out the old grease and clean everything, repack, and reassemble. Be advised the balls in the bearing will probably try to escape so be ready...
This is an endemic problem with SX-100s, particularly. With the GPR-90 I'd suspect ground points. Tighten em up. Finally be sure you got BOTH faces of the bandswitch switch wafers. You're doing it absolutely right, but it often takes more than one pass to get the crap cleaned off. Title: Re: Band Switch Cleaner Post by: Steve W8TOW on January 24, 2014, 11:24:14 AM Great thoughts guys, will pursue these approaches! AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
73 Steve 8tow |