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Advice for restoring 38-12
#1
I've always liked the looks of the wood art deco radios and recently bought a couple of Philcos - a 38-12, 38-620 and a 48-250 Transitone....with the hope of restoring them....in my spare time. Got the 48-250 working by re-capping. I grew up withoneof these on our kitchen snack bar ...so was xcited that I got it working. Started on the 38-12and it really needs help...power tranformer primary open, field coil measures 70 ohms, audio output transformer...open primary.

My question.....I have a Rider's for the 38-12...but no specs are given for these components. Is it possible to find the specs for these to find modern equivalents...or do you just hunt around for other models that use the same parts and hope to find good ones..? Don't want to give up...but not sure how to proceed.

Thanks for your help
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#2
Hi

Odd that your Rider's does not give specs for the field coil? Usually Rider merely copied the service bulletins provided to him by Philco, and the bulletin for Model 38-12 shows a field coil of 1500 ohms.

Specs for the power transformer, per 1941 Philco parts catalog:
High voltage secondary: 516 volts center-tapped, 50 mA DC
Filament winding: 6.3 volts @ 2A

Specs for the audio output transformer, per 1946 Philco Quick Selector Parts Directory:
Primary impedance 8000 ohms; secondary impedance 3.5 ohms; 3 watts; turns ratio 44:1.

You should seriously consider buying a copy of the factory service info from Chuck; he not only supplies a copy of the original Philco service bulletin, but also an extra-large copy of the schematic, and includes any pertinent changes.
http://www.philcorepairbench.com/schematics.htm

MUCH better info than found in Riders, and at a reasonable price.
--
Ron Ramirez
Ferdinand, IN
Я этого не понимаю
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#3
I will check out the schematics...and thanks for the parts specs.

Can you advise on a good source for modern replacements....? Or...is it better to keep it as original as possible..?
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#4
http://www.philcoradio.com/resource.htm

You will probably find suitable replacements for the audio and power transformers from Radio Daze; or, if you want used originals, try Play Things Of Past.

The speaker is a different issue. Here, you have three choices:

1. replace with a modern PM speaker, substituting a 25 watt resistor under the chassis for the field coil; or

2. seek a good original speaker from a source such as Play Things Of Past, or a pull from another 38-12 chassis; or

3. have the speaker field rewound by a speaker repair shop.

Good luck. With all these problems, you may consider trying to find another 38-12 chassis with good parts, and using the one you now have as a parts donor?
--
Ron Ramirez
Ferdinand, IN
Я этого не понимаю
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#5
Another part you might want to check out is the oscillator transformer for an open winding. My set had an open winding and the parts set I bought had a bad one as well. Ended up putting a new winding on it and worked well after that. Had an open antenna coil as well and the parts set one was damaged and bought a universal replacement from AES for that.

Here is a link to some Philco documentation for that set:
http://www.audiophool.cjb.net/Misc/philco_38-12.djvu

You'll need a DJVU viewer to open them. I'd also recommend using Chuck as a source of schematics as his information is more complete than most you find posted on the net.
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#6
Just processing the order for the 38-12 and the schematic shows Field Coil at 1,500 ohms D.C.

Primary winding of output transformer is 450 ohms. Nothing given for secondary. If a winding is
open it will be the primary where all the DC current is for the output tube plate.

Most likely, either cap #21 shorted or the 41 output tube to pop the primary winding open.

Chuck
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