[Hallicrafters] Help with SX-42

[Barry H]

Hi Ed

Have you seen all the info at http://www.antiqueradio.org/halli07.htm ?

Scroll way down the page and there's the account of A. B. Bonds about this or very similar situation.

A bad cap may have caused arcing and the wafer or rotore may be carbonized.  If so, you may be able to scrape away enough of the char to remove the short -- or "accidental resistor."  If you can see the blackened area -- with a flashlight, you may be able to scrape it with an Xacto knife or similar tool.  

Another thing they say is that the dirt buildup can cause shorting and arcing on that bandswitch.  The carbon track might be on/around the rotor, or it might be on one place on the wafer and the shorting action is occurring through the wiper(s).  

There is also mention of reparing a broken wafer -- something about raising up the bandswitch by unsoldering some of the leads.  Maybe you could use that technique to get at the switch without removing it.

I suppose the short could be in some other component giving you that reading -- you might have to disconnect one or more leads to isolate the wafer and rotor to check that.  

Whatever -- I suggest going to that link and give it a read through if you haven't seen it before.  Hope it helps.

Anybody ever hear from A. B. Bonds lately?

Barry


Hi, it's me again;

I won't say how many days I spent looking for a short in subject. I found
B+ on the 2nd RF amp control grid (hard on 6AG5's). After deciphering the
schematic which shows each bandswitch wafer in 2 places with only one row
of contacts, some making to the front rotor and some to the rear rotor
and some to both, I found 500 ohms leakage from the front rotor (2nd RF
grid circuit) to the rear rotor (1st RF plate circuit) on wafer 1H-1HH.
It looks impossible to work on it in place and just as bad to get the
wafer out. Has anyone run across anything like this, and what did you do?
Any suggestions for getting the wafer out? Drill out the rivet and pull
the center flat shaft out the hole in the back of the chassis? Any advice
will be much appreciated.

73, Ed Richards K6UUZ