SB-401/SB-303: not working right since storage

[Robert Myers]

Hello all,

I have a Heathkit SB-401 and SB-303 pair that used to function perfectly together (Tx frequency locked to Rx frequency due to lack of full set of crystals for the SB-401).  I have two problems that someone may have already experienced.

After 7 years of non-use, here is what happens when I key the SB-401: I get a loud "pop" out of the speaker --- BTW, when paired like this, the speakers audio comes from the back of the SB-401 RCA phono connector.  The SB-401 gets this audio feed from the  SB-303's audio output though an RCA to RCA phono cable  --- but I'm not sure if it's just looped though the SB-401 from the SB-303.  The loud "pop" continues occurring briefly every second, third, or fourth key down --- randomly really, but often.  I key down for 0.5 second every 10 seconds, to give the SB-401 Potter-Brumsfield  relay a chance to go back to its 'normal' state for before each test keying).  Does anyone know what's going on here?  I was thinking that the SB-401 relay was not causing the receiver to mute properly --- but that's just a guess.  Maybe the relay IS really working, but the SB-303 is not responding to the mute signal from the SB-401.  I don't know.

The next problem I have is that I have to wiggle that band selector switch in the SB-303 constantly to get it to show the proper frequency on my SB-650 digital frequency display.  Very tricky and frustrating to watch the SB-650 bounce around all over the place.  I have "cleaned" the rotary band wafer switched with "Red Cramolin" drops (I believe that is now called 100% concentrate DeOxit from CAIG labs).  No change.  Very frustrating.  I thought the DeOxit products were suppose to be the best on the market --- God knows, they have enough variants of it on the CAIG labs web site.  I can't say the wafer switch's contacts actually looked any cleaner or shinier after applying the DeOxit and flushing --- but maybe they aren't suppose to (to the human eye).  Does anyone know of a better contact cleaner?  Is this "wiggling the band switch" a common problem?  If so how did most of you fix it --- if at all?  Should I just keep blasting the switches with say 5% concentrate DeOxit --- i.e., use
the whole can on them (with absorbent cloth laid down liberally everywhere else to protect other things from the splatter and run-off?

Any ideas for solving this problem?  Does it ring a bell with anyone.  (I also attempted to clean the relay in the SB-401 as well).

Thanks,
--- Rob

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