Hallicrafters SX-42 Refurb

Just the beginning...

Got started with this by attempting to put a set-screw in the tuning knob. Turns out: no set-screw goes there! The entire tuning/bandspread setup was messed up to begin with. The hole in the (brown) tuning knob is there only to provide access to the two Bristol set screws in the underlying (silver) bandspread knob. (photos to come).

Late July 2009 - Finally, Inspection Time. Serial Number: HA-92906.

  • Fortunately - the bandswitch looks good, from a first inspection. There appears to be no burning on any of the contact points, so this might be a keeper
  • An audio transformer has been replaced. Whoever did so (in the past 60 years), used a generic output transformer - a nice one - but several of the unused output lines are just hanging. Thats a bit of a hazard
  • The fine-tune dial-string gave up the ghost after a few turns. About time, old codger.
  • "pin 5 of the 6H6 AM detector" - is NOT connected, making this a LATE model. This eliminates quite a few versions of the schematics.
  • A Build Date! Stamped on the back of the bandspread dial: Feb 17, '48.

Completed So Far

  • Inspected and cleaned.
  • The complex tuning knob mechanism was disassembled and lubricated.
  • Dial Cord was Re-strung.
  • Replaced all the lamps with correctly sized new lamps.
  • Started Replacing Capacitors — radio now works (partially) on AM and FM Broadcast!

This radio is a huge project. Everything is heavy or difficult to reach or unique, so I'll be adjourning until winter...

Update - October 2012

Still waiting for some available time and space to work on this find old rig. But: From Flavio Betti, in Brazil comes this contributed SX-42 Schematic. It's marked with the 'variant' 89D210K, and it's much cleaner than any previous scans that I've found at the usual manual an schematic sources.
SX-42 Schematic - Click on the Image for Full Size

Full Service Manual, generously pointed out by Steve Gajkowski, KD3HT. (Thanks!) This looks to be a Service Manual for the "Run 2" variant:

"January 1949, 94X317, Run No. 2, SEE CHASSIS STAMP"

Note the title page indicates that now Hallicrafters is part of Northrup Corporation.

SX-42 HF-VHF Receiver Service Manual