Hopefully this will help someone else. I just recapped and tuned up a Stewart Warner 51T46 and initially it sounded great. I noticed the lamp sockett was bad so I replaced it and didn't think much more about it. Next time I turned the radion on, I had significant AC hum. Turns out that the original lamp socket was isolated from the chasis, but the replacement socket (metal) was not. I put in a plastic lamp socket and all is well. Just be carful and aware because the replacement socket ties chasis ground to AC. This may be a common concern for radios that use the 35Z5 tubes, or even others.

Yes Bruce, I have come across this before. I restore a lot of the old Hallicrafters radios. The S-38 line some have hot chassis, others use a B- buss. someone had replaced the dial lamp socket with a single wire type on one with the B- buss line. It had a hum like that. I replaced the socket with the two wire kind. No hum now.

Sounds like you didn't check to see how the set was wired before replacing the socket. Not a good idea to jump in and replace parts until you are sure how they are used. You cound have had a big surprise.

:Hopefully this will help someone else. I just recapped and tuned up a Stewart Warner 51T46 and initially it sounded great. I noticed the lamp sockett was bad so I replaced it and didn't think much more about it. Next time I turned the radion on, I had significant AC hum. Turns out that the original lamp socket was isolated from the chasis, but the replacement socket (metal) was not. I put in a plastic lamp socket and all is well. Just be carful and aware because the replacement socket ties chasis ground to AC. This may be a common concern for radios that use the 35Z5 tubes, or even others.

:Sounds like you didn't check to see how the set was wired before replacing the socket. Not a good idea to jump in and replace parts until you are sure how they are used. You cound have had a big surprise.
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