42-390 - Printable Version
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42-390 - Guest - 08-05-2010
A family member has a 42-390 radio which is not working. I "volunteered" to try and repair it. His chassis was in bad condition.So I purchased a 42-390 which is in good physical condition as far as the wiring and components (caps) are concerned.All tubes fire up except the 7X7 tube (which was subituted for the original XXFM tube). It is supposed to "glow" like the other tubes , right? I was told by the seller (well known antique radio co.) that it worked on B bands. But I have not been able to get sound out of it. This is my first attempt to work on an antique radio, I am a computer tech w/ 35 + years of repair, with t/s to board level experience. Where can I get a manual with test points to T/S . Would the fact that the 7X7 tube is not "glowing" keep the radio from generating sound on all bands? Do I need to replace the 7X7 tube? Any thoughts on how to proceed will be greatly appreciated. Thanks, Joe
Re: 42-390 - codefox1 - 08-06-2010
The 7X7 is same as XXFM tube. Test for filament continuity (pins 1 and 8 of the tube, and it's socket as well for filament voltage.) This is a small signal tube, and will not become very warm in use if it is good.
You can get a schematic on this forum.
Replace all the electrolytic capacitors, as well as the paper ones as well. They're over 50almost 60 years old!
More help available here and elsewhere.
Re: 42-390 - Ron Ramirez - 08-09-2010
The XXFM is the 2nd detector for AM and FM, as well as the first audio amplifier. If it does not light up (burned out? bad tube socket contacts?), the radio will not work.
If you really want good service information for your 42-390, visit Chuck's site.
http://www.philcorepairbench.com/schematics.htm
Excellent info, reasonably priced.
Re: 42-390 - Guest - 08-10-2010
Thank You..