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Wow! That was freaky! I picked up the 2 tubes i required to finish overhauling my Hallicrafters S 38, Installed them and bench tested the radio. Worked great! Caps and Electrolytics replaced, all switches cleaned and lubricated and several lengths of crispy wires replaced and a handful of resistors. I put it back into it’s metal case and take it up to the master bedroom because I have a wire strung up and want to try the shortwave. I attach the radio to ground and hooked up the antenna wire. I turn the radio on and the lights dim in the room accompanied by a zapping sound and smoke pouring out of the radio. Continues to burn with flames after I turn it off and even after being unplugged, the fire continues to burn until i finally manage to huff and puff and it goes out. I carry it’s smoking carcass out of the master bedroom, down two flights of stairs and back into the shop. I run back upstairs and open all the windows in the master. On the way past my wife, I mention she may notice a really acrid smell in our bed room (and it isn’t my socks). Her eyes get wide and she asks me if it’s common for tube radios to spontaneously combust ? And I say no of course not, just a fluke. I pull it back apart and see that the on/off volume switch has had a major meltdown. Fortunately, the damage seems to be confined to only the switch without any shorted wiring anywhere else in the radio. The on/off vol switch did behave strangely before I cleaned it as the radio wouldn’t turn off. After giving it a good shot of cleaner,(2 days ago so it should have been dry inside) it seemed to work fine again. Can I assume because there is no burnt wiring leading to and from the switch that the problem rests with the switch itself? Possible mitigating circumstances. 1) It was the First time I added ground and there was a little bridge I didn’t spot from antenna (2) to ground (see pic). I doubt that could be a factor as there was no damaged wiring in that area. 2) It has failed grommets that may be there to isolate the metal case. (See pic) again, it didn’t burst into flames when I initially tested it. Thanks for your opinion in advance, Gary on fire in Montreal.
Don’t you just hate that! 🙂
Radiomuseum.org has a lot on the S38, including the pdf attached, which talks about AC hum causes, and mentions both the switch and the mounting grommets. It looks like the mounting grommets need to have almost perfect insulation otherwise hum develops at high DC resistance. If there’s a total short between the case and the chassis, then what happens probably depends on where you connected the ground. Where did you make that connection?
The antenna-to-ground strap is not the problem: that strap is used when you have a long-wire type of antenna. With a balanced antenna you would remove it.
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Gary,
One of these may be what you need. They are a 2 wire GFI style plug. I find them at surplus places and 2nd hand stores on various types hair dryers and straightners.
Interesting article on them here – https://people.ohio.edu/postr/bapix/GFCI_.htm
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John,
That’s a great all in one solution! I will go with that. Thanks for the link. It speaks volumes That 2 of the radios pictured are Hallicrafters and 1 is a S38!!
I had to jump on the radio this morning as I had to know if there was any collateral damage. Found a NOS pot in my stash and cut the shaft to fit.
Replaced the pot and all the adjacent wiring that got crispy. Radio plays great ! What a relief. I will mount a separate toggle for the on/off. Time to play (safely) outside. A rare nice sunny and warm day in Montreal and too nice to spend in the radio cave.
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