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Old 09-27-2008, 05:33 PM
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radiotvnut radiotvnut is offline
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Location: Meridian, MS
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I do see one minor detail that needs to be taken care of. That blue finned thing on the front of the chassis is a selenium rectifier. It is used to convert the incoming AC voltage from the wall socket to a DC voltage. These do tend to short and arc. When they do, you'll get a foul odor similar to rotten eggs. I've read that the fumes cam be toxic if you are exposed to them for extended periods. The good news is that this selenium rectifier can be replaced with a modern silicon diode. Something like a 1N4007 or any other diode rated at least 400 PIV @ 1 amp will work. Just unsolder the leads of the original selenium rectifier and remove the rectifier from the chassis. Mount a suitable terminal strip to the chassis to solder the silicon diode to. The only thing you'll need to do when using a silicon diode rectifier is place a resistor in series with the diode. Silicon diodes have less voltage drop than the original selenium rectifiers and failure to use a resistor may result in too much B+ voltage. I'd say a 68 ohm, 5 watt resistor should work. Just connect one end of the resistor to the incoming AC lead. Connect the other end of the resistor to the anode terminal (anode is the end without the band) of the diode. Lastly, connect the cathode terminal (end with the band) of the diode to the remaining lead that goes to the filter capacitor. Make sure your connections are soldered good and see to it that the resistor will not come in contact with wire insulation, etc. These resistors do get a little warm.

Also, if there is a capacitor connected between one side of the AC line and ground, that should be replaced. In this case, it's probably a bumblebee cap. It will be black with colored bands around the case. Those bumblebees were not great to begin with and they are known to blow up, especially when used in line bypass applications. www.justradios.com sells about any kind of capacitor that you'll need for old radio restoration, including special safety caps that are designed to be used safely in line bypass applications. Capacitors are inexpensive and that's why I usually change any line bypass, wax paper, and electrolytic caps that I find in vintage equipment.

Of course, those parts I mentioned could work for another 50 years or they could go belly up tonight. You'd be better to just go ahead and change them just to be on the safe side.

Oh yes, that radio (along with many other radios from this time) has a "hot" chassis. That means that one side of the AC line is connected directly to the chassis. That means there's a 50/50 chance (depending on the AC plug position) that you have 120 VAC on the chassis. This will not pose a threat as long as the radio chassis is inside the cabinet. The ideal way to work on one of these outside of the cabinet is to power the chassis via an isolation transformer. Otherwise, use extreme caution.

I didn't tell you all of this to get your GF on your back. This is stuff that everybody entering the hobby of vintage electronics needs to know in order to get the most out of their equipment and to help insure that they live to an old age.
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