Electronics 20

Picked this up on ebay back in March 2004. Tag says it's a Stewart Warner serial number 43. I spent about two years rebuilding this unit, module by module. I didn't do it all contiguously, I'd do a module, then work on some other project, then come back to this and do the next module. Thus it took a couple years to complete. But boy is it a beautiful radio. It's a marvel of both electronics engineering and mechanical engineering. probably one of the best HF receivers ever made. We did have a couple of these on the USS San Jose when when I served aboard. We never really had to do anything to these radios. They just worked all the time. Actually we were a little intimidated by the mechanicals at the time. I remember it looking like a Swiss watch or an automatic transmission or something. None of us wanted to mess with that. But not anymore. I tore this one all the way down and rebuilt it. Not really all that intimidating at all.


Here are the original pictures of the unit. These were right off of ebay. This is how it looked when I got it. Underside looked great. The top however was pretty dirty. I never did fire it up before rebuild. I heard to many horror stories about bad caps taking other things out like mechanical filters.

The first module I did was the power supply. However, I lost all the power supply pictures when transferring them from one computer to another. Windows did that for me, thank you Microsoft. So I don't have any pics of the power supply rebuild. Next module I did was the Audio Deck.


Here it is finished, rebuilt. I replaced all the carbon comp resistors with new metal film resistors, I always do, the carbon comp resistor change value to much I don't trust them. I reused the original wiring harness. I did have a bad remote output transformer and had to get a replacement from Fair Radio. I also installed the AF LF Mods which involves changing several coupling cap values to improve the LF response. I did not do the 6AQ5 conversion. Next up is the IF Deck.



Here it is rebuilt. The components are really packed in there. It took quite a bit of planning, looking at pics, drawings, and the schematics to get the parts back in there. I again reused the original wiring harness as well. Again I replaced all the carbon comps with metal film resistors. All the caps were replaced. I installed the SSB AGC mods described by Lankford that involved adding diodes in parallel with R546 and R547 as well as adding a 47pfd cap in parallel with C535. By the way this unit receives SSB very well in my opinion. Once set it is very stable and requires almost no tuning adjustment to keep the audio legible. I really don't see the need for a product detector mod or add on to receive SSB with this receiver. One other thing of note. After washing the bare chassis with plain old soap and water I used finger nail polish to cover all the writing on the chassis. It preserved the chassis labeling very well when doing the bare chassis with fine steel wool. Ya I know. the steel wool does and did remove the anodizing. I also did the replacement of the S-Meter pot with a 10 turn pot. Next up was the PTO. However, again these pics were lost when transferring them from one computer to another. Windows did that for me again, thank you Microsoft. So I don't have any pics of the PTO rebuild. Next time I have the radio apart I will take some pics of the completed PTO so I can at least put them up. After the PTO I did the 2nd LO.



Above pics are disassembly. I completely took it down to a bare chasses.


Above pics are prior to rebuild and coming apart. I did take it down to a bare chassis as I do. You can see those nasty BBOD's.


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