RadioBanter - View Single Post - sx-28 restoration ongoing

jakdedert · June 1st 08, 11:17 PM posted to rec.radio.amateur.boatanchors

wrote:
Thanks to Phil Nelson and many others for great internet
documentation and numerous usenet posts regarding the SX-28. I
followed Phils RF deck instructions and re-capped my radio, which is
currently still on the bench. I also have a sx-28 parts radio which
has been invaluable
for various mechanical repairs. Even after re-alignment, the radio
still needs help, however. It has a mod using a 6sn7 where the 6j5
should be, along with an internal switch. I'm guessing it is a product
detector, and I'm having so much trouble with this radio with AVC
problems and intermittent sensitivity, and s-meter issues, that I've
decided to restore the original detector with a 6j5 and try to rebuild
the section using the schematic and the parts deck as a guide. It is
an intimidating undertaking, though. The schematic shows no pin
numbers for the tubes, and the wire re-tracing is tough, since their
color coding is long gone. I'm considering buying another working
radio to use as a guide, and then when I finally have two working
sx-28's, I'll sell one of them off. However, I'm sure there are enough
production variances to not completely rely on the copy. After
numerous successful restorations on other radios, this one's been an
abyss that I seem to be falling into far deeper. Any old articles on
product detector mods for the sx-28 would be great to read to assist
in un-modding this thing!
Thanks!
Ben

I've never attempted something so complex as a complete rebuild of an
SX-28; but I'd suggest you go through the schematic with a tube manual
and mark all those pin numbers as a first step.....

jak