Hey all, I got a nice Philco 650. The person I got it off of said they plugged it in and it smoked, so, replaced all the paper caps, checked resistors, brought it up slow and found that the rectifier tub an 80 tube glowed like a light bulb , actually, when inspecting the radio, there was an 83 in there so I put the 80 back in. Anyway, I pulled the 80 tube and everything seemed fine, the tubs all light nicely, the shadow box light lit, no smoke. Any ideas?
Thanks, Eric
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Is the filaments bright or are the plates of the 80 glowing?
If its the filaments then I would check that your getting 5v on the filaments from the power trans. Did the power trans ohm out ok?
If its the plates glowing, then you got a short or something down stream that is pulling major current. Shorted E-cap?
The 83 tube is different not only does the filaments pull more current at 3amps (80 only 2amps) but the 83 is a mercury vapor rectifier.
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If someone told me that something smoked I would not be plugging it in, and powering it, slow or not, before I took the meter and tried to see if there is a short or high load to the rectifier.
Also, why "all the paper caps?" and not ""electrolytics"?
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morzh is right if you didn't replace the e-caps then one or more of them could be shorted and that will put a serious load on the 80 tube and the power trans.
Looks like there are 3 e-caps on the set a dual #77 on the schematic which is an 8uf and a 10uf, and a single #78 which is an 8uf. All of these can be replaced with 10uf modern caps @ 450v.
Replace those caps before trying to power the set again, also if I were you I would ohm out the power trans to make sure it wasn't damaged at some point.
Schematic here:
http://www.nostalgiaair.org/PagesByModel...013824.pdf
If you need a clearer copy PM me.
(This post was last modified: 03-23-2013, 12:50 PM by
Keith.)
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Once all is replaced, I would simply smell the power transformer. If it smoked it usually keeps the smell. And if it did, it needs to go even if it works for now - smoke means damaged paper and damaged wire laquer so it is then a question of time when it will smoke on its own.
If it does not smell, then try to measure resistance although I am not sure where to get the data against which you can do the measurement, as it is usually fairly low resistance, and the primary often looks like a short even if it is OK.
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MV rectifiers may glow blue as the mercury vaporizes I know 866 tubes do. This is normal but if the 80 glows red that's a problem. If the 80 glows blue that indicate that it's gassy and may short usually indicated by sparks between the plate and filament.
Terry
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