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Old 01-19-2018, 07:27 PM
Phil Phil is offline
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Philco 48-482 - interesting find

I'm in the process of restoring a 48-482 to operable condition. The first
One I bought had a bad power transformer. (Did philco have the worst transformers or is it just my bad luck) I am now starting on the second one and intending to combine the best elements of the two into one good unit. Anyway, today I replaced the electrolytics and powered the set up. Normally, I wouldn't put power on it until replacing all paper caps and any resistors anywhere near out of tolerance, but in this case I wanted to confirm the power transformer was good and the audio output transformer was good. (Just finished a 42-355. Had two chassis and open primaries in the audio output transformer of both) Having replaced only the electrolytics I fired it up and was able to receive stations on AM, SW and FM. All good, right? The FM seemed very weak audio wise and intending to do rebuild the whole thing and do a complete alignment anyway I turned the coil and capacitor in the FM1000 circuit a bit.... didn't have any effect. I was able to receive several strong local signals. I looked at the FM1000 tube and it was in fact a XXFM! Soneone had also soldered the FM bandswitch so it couldn't move. I had previously repaired this mess. So the switch was working. It seems at some point someone, for whatever reason had given up on FM, soldered the bandswitch so it couldn't go to the FM position and put a XXFM in place of the FM1000, in spite if the fact it would now do nothing. The amazing thing is receiving several strong local stations in spite of this. I haven't looked at the tube pin out yet, but I'm assuming, by accident, some tube elements are providing a slope detector on FM?
I thought it was interesting.
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Old 01-20-2018, 09:45 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by Phil View Post
I'm in the process of restoring a 48-482 to operable condition. The first
One I bought had a bad power transformer. (Did philco have the worst transformers or is it just my bad luck) I am now starting on the second one and intending to combine the best elements of the two into one good unit. Anyway, today I replaced the electrolytics and powered the set up. Normally, I wouldn't put power on it until replacing all paper caps and any resistors anywhere near out of tolerance, but in this case I wanted to confirm the power transformer was good and the audio output transformer was good. (Just finished a 42-355. Had two chassis and open primaries in the audio output transformer of both) Having replaced only the electrolytics I fired it up and was able to receive stations on AM, SW and FM. All good, right? The FM seemed very weak audio wise and intending to do rebuild the whole thing and do a complete alignment anyway I turned the coil and capacitor in the FM1000 circuit a bit.... didn't have any effect. I was able to receive several strong local signals. I looked at the FM1000 tube and it was in fact a XXFM! Soneone had also soldered the FM bandswitch so it couldn't move. I had previously repaired this mess. So the switch was working. It seems at some point someone, for whatever reason had given up on FM, soldered the bandswitch so it couldn't go to the FM position and put a XXFM in place of the FM1000, in spite if the fact it would now do nothing. The amazing thing is receiving several strong local stations in spite of this. I haven't looked at the tube pin out yet, but I'm assuming, by accident, some tube elements are providing a slope detector on FM?
I thought it was interesting.
That set had a form of oscillating FM detector or a "locked oscillator" as Philco called it. It seems to be similar to the quadrature detector used in the newer TV's. They only seemed to use it for one or two model years.
The radio was $150 new. A lot of money for the time.
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