[Hallicrafters] SX-62A

[J.G. Hoffman]

Jeff,

 
I currently have an SX-62A upside down on my work bench.  You are on the right track.  A good tube check will help.  Be sure to use safe HV practices, the unloaded transformer swings up to 300V, and can deliver a fair amount of current to drive the 6V6s.  Here is what I have found so far:
 
1) Start with the power supply.  If the 6V6s are not working the voltage will swing up to 280 or more.  But there should be at least 250+ B+.  (I noticed a little statement that all voltages were measured with a 20,000 ohm/volt VOM.  A VTVM or modern DMM will read higher). I found the electrolytics in the PS needed to be replaced, so I replaced all electrolytics, even in the cathode bias circuits.
 
2) Work backwards from the audio stages toward the front end to find which stage is dropping the ball. 
 
3) Squirt cleaner/lubricant into all switch contacts and pots, dirty band switch contacts were limiting reception on my boat anchor.  Also clean and lubricate the contacts on the tuning capacitor and blow all the dust out between the plates.
 
4) I am replacing all the tubular capacitors on my rig.  I used disks on the PS, RF, and IF circuits and mylar ("orange drop") caps in the audio.  I worked from audio section back to the RF, checking to make sure I didn't make a mistake after the changeout in each stage.  I figured it would be easier to know where to start trouble shooting if I got something mixed up.  There are several in the RF stages that are under the band switch, I haven't figured out how to do them yet.  Removing the band switch looks to be difficult and easy to mess up the reinstallation.  I am looking for a really long skinny soldering iron and pliers.  As I tested after each replacement the reception got better and better.  Apparently many caps were marginal and dragged down the performance with out completely shutting down the stage.
 
5) I noticed a lot of out of spec resistors.  Plan to start on them next.
 
6) Right now I'm concentrating on the electrical.  Another contributor suggested "Blue Magic" for the chassis, I am not familiar with it.  The auto body shop wanted $250 to blast the rust and repaint the cabinet.  I am investigating Naval Jelly and Rustoleum.  It isn't looking as good, but if the radio is in between other things maybe it won't show.
 
I hope that helps.  Mine is turning out to be a big summer project.
 
Joe

 
 
 
--- J.G. Hoffman

--- drjgh at earthlink.net

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