Allied AX/SX-190 Amateur and Short Wave Receiver Info

When I was a kid I liked to listen to short wave radio stations from all over the world on radios I built from kits and later from scratch.  I eventually got a amateur radio license (expired now) and collected a lot of old radios because at the time that was all I could afford.  I had old Halicrafters sets, a bunch of different military surplus radios, and eventually I got an Allied SX-190 short wave radio. 

The SX-190 is a really nice SW receiver.  The huge, heavy tuning dial spins ever so smoothly and it is the most precise analog tuning I have ever seen in a radio.  I think it was the last of the quality analog tuned radios.  After that PLLs and digital tuning took over.

A few years ago I started to wonder what ever happened to that SX-190.  I guess that I must have traded it or sold it.  I got the itch to get another so when I spotted one at the monthly electronics swap meet in Dallas I bought it.  I think I paid $75.  You can usually find them on ebay for about $100 or so.

My "new" SX-190 worked well for several months, but then suddenly died.  I started looking around the web for service info and found the schematic and eventually the entire service manual.  I kept looking and ran into copies of reviews and modification articles from radio hobbyist magazines.  I started collecting all the info and eventually put it all together into a .rar archive file you can find here and at a couple other locations around the web.

I eventually managed to repair my radio.  I traced signals through the circuits and found that one of the crystal filters in the IF stage was not passing the signal.  I thought that I had a dead IF filter and started looking for a replacement.  After giving up in frustration, I decided to unsolder the filter and see if I could spot anything wrong with it (fat chance!).  Nope.  So instead of risking losing the thing I soldered it back on the PCB.  The radio started working like new again.  It was a bad solder joint!  Unfortunately this happens to most old equipment, and a lot of not so old equipment, especially if it uses printed circuit boards.