[Heath] AR-3 Tuning Cap

[Al & Dottie Skierkiewicz]

The capacitor does not contain "gear reduction" in the true sense of the word.  The inner shaft connects to the outer shaft through ball bearings.  As the inner shaft turns, the balls turn and then so does the outer shaft.  The reduction is the difference in the diameter between the OD of the inner shaft and the ID of the outer shaft.  If the lubricant has hardened, the inner shaft and outer shaft spin at the same time, no reduction.  Most of the reduction drives operate this way.I am rebuilding an AR-3 right now.  Much of the receiver uses the tube sockets riveted to the chassis for ground.  As the receiver aged, these became high impedance and therefore ground bypass circuits became less effective.  That includes the tabs on the power supply filter.  I also experience the hum in BFO position that varies with RF gain.  
I once owned an AR-3 when I was in high school.  I purchased it used from the Radio TV Lab on Irving Park in Chicago if you lived on Chicago's north side.  I found one at a Milwaukee hamfest a few years ago, I didn't even haggle the $30 price tag.  When I got it home it made hum but I could only pick up WGN radio, the closest BC transmitter to my house.  After a little troubleshooting, I came to the conclusion the receiver had been built but never aligned.  I found some wiring errors as the builder kept doing mirror image translation when wiring from the top of the chassis to the bottom.  With alignment, things started picking up but as I worked, one day I would have sensitivity and the next day almost nothing.  It was then I discovered that whacking the chassis and then the IF cans in particular, changed the sensitivity.  (this is referred to as "thunder" in some rebuilding publications)  With a little research, I found the dreaded silver on mica caps in the IF cans.  Yes this one had the silver that migrated to other parts, high impedance connections in the clamp, etc.  I am rebuilding the IF cans with silver mica dipped caps and hope for better performance.  This part of the project is taking longer than expected as I also mentor high school robotics and that is taking most of my free time.I recently purchased a QF-1 Q multiplier for this radio.  The "mirroring " problem also hit on the accessory socket so I had some rewiring there as well.  I cannot get the Multiplier to function at this point in any function.  I do get noise and hum when I switch but that is it.  Strange as it may seem, the same person may have built both units.  I replaced the RG58 to the IF stage and I get all the right voltages.  I have never used a Q device so I am still learning on that.  My suspicion is that the IF is so far off frequency due to the bad IF caps, that I may be out of the passband with the Q Mult.AlWB9UVJ
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