The PHILCO Phorum
Philco 42-395 Transformer Help - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Philco 42-395 Transformer Help (/showthread.php?tid=12743)


Philco 42-395 Transformer Help - Jason K - 07-20-2015

I am in the process of repairing a 42-395 for a customer that had plugged it in and turned it on before he brought it in.  Therefore the Power & output transformers are cooked as well as associated wiring and rectifier socket.

One thing I do know is the transformer only has 2 secondary windings. It has a hv center tapped winding and a 6.3vac 4-5 amp winding. This unit uses a 7Z4 rectifier and 7C5 audio outputs have replaced the 7B5.

I would like to know how to calculate the voltages to find a transformer that will be close.

Any & all help is appreciated
Thanks
Jason

RE: Philco 42-395 Transformer Help - Radioroslyn - 07-20-2015

Well you can figure about 10ma per tube for the HV except for the output (20ma ea) and the 7Z4 (0 ma). That puts you at about 90ma. Voltage wise you need about 200vdc so figure 250-0-250vac.

Terry

RE: Philco 42-395 Transformer Help - Jason K - 07-20-2015

Hey Terry Thanks so much. I was leaning toward a 500vct transformer.  The problem with modern transformers is that the 6.3vac winding usually is not high current.  In this model the 6.3vac winding needs to supply around 5 amps including lamps and rectifier.  I have found 2 that might work:
I have found an edcor transformer # XPWR093 it is 500vct @ 300ma, 6.3vct @ 7A.
I know the 300ma is probably overkill, but would this work?
Also found edcor# XPWR072 550vct@250ma, 6.3v @ 7A. The 275-0-275 maybe a bit  too high though.

RE: Philco 42-395 Transformer Help - Ron Ramirez - 07-21-2015

The original power transformer part # is 32-8192

HV secondary: 640 VCT @ 90 mA
Filament: 6.3V @ 4.5A

Output transformer is 32-7997

Primary impedance 12,000 ohms push-pull
Secondary impedance 5 ohms with a 7% feedback tap
10 watts
Turns ratio 46:1

From the 1946 Philco Quick Selector Parts Directory

RE: Philco 42-395 Transformer Help - codefox1 - 07-21-2015

You can always lose the rectifier tube and use diodes instead which will reduce filament load. Also it is unusual to have both power and output transformers fail (at the same time?) Nothing to lose by partially disecting and look for corroded connections; output transformers are notorious for this.

RE: Philco 42-395 Transformer Help - Jason K - 07-22-2015

Thanks Ron for the info.  With this info. I was able to find a replacement Hammond or edcor.  

I Appreciate all the help.  

I found a replacement tranny that will supply 5A @6.3v. This gives a little wiggle room and if I use #47 lamps the current will be 200ma less.

This model also has prewar fm.  So I will be building a converter for it also.

Maybe I can track down a 10 button faceplate, as usual the plastic has shrunk and pulled out the screws.  
Thanks
Jason