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Philco 90 filament section on PT bad
#8

Well I have checked all the ohms in the tubes, they are around .1 to .2 when cold.  As I took a tube out the ohms slowly dropped by roughly 1.8 to 2.0 ohms per tube.  It is what I would expect since the filaments of the 24 and 27 tubes draw about 1.7 amps each.  Voltage also slowly went up as the tubes were pulled out of circuit one by one.  I have a few dozen 27 and 24 tubes and have tried roughly a dozen or so.   All with the same results.  When I had the transformer in after recap, the radio played for couple of weeks on my test bench for a few hours.  Then one day while listening to it it just faded away, then after a few mins would fade back in.  I kept watching it and noticed the filaments would dim as it faded away.  That is what made me look at the filament circuit and then the windings.  Also I noticed the transformer after an hour or so would get hot.  But so far while just testing the transformer out of the radio, it has not gotten warm.  

Could it be the filament windings are ever so slowly failing, but I cannot detect a short yet.  It just cannot hold the volts as the load goes up.  


Messages In This Thread
Philco 90 filament section on PT bad - by Skip - 04-02-2016, 01:08 PM
RE: Philco 90 filament section on PT bad - by Skip - 04-02-2016, 07:46 PM
RE: Philco 90 filament section on PT bad - by OZ4 - 04-03-2016, 11:02 AM



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