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Philco 41-296 Troubles - Printable Version

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Philco 41-296 Troubles - w5ami - 04-03-2013

[Hope I have posted this in the proper place]

I am restoring the chassis on this radio and have replaced all caps (except micas for now), and most all resistors. Those I have not replaced were well within spec.

I aligned the IF with no issues, however I am not able to hear the fundamental at 1500kcs or 550kcs from my signal generator no matter where I adjust 16 and 17. I have heard, what I think is a harmonic, and if I spot it on 1500kcs, I hear no stations in the BC band. However, I can detune 16 and hear BC stations, but they are very broad, like 100kcs+, so something is obviously amiss.

Assuming everything else is correct, Osc transformer (checked), etc., what should I be looking for. Only mica cap I've found way off is 4, which reads about 105pf and should be about 250pf. Currently don't have one to replace it with. I have also checked all the IF transformers and found them to be right in spec., no open windings, etc.

Another odd thing was a wire installed on the antenna coil wrapped at both ends connected to, I think, 7 and 5 taps. I am assuming it was a "gimick cap" for something. I removed it, however not knowing what it was for, should I replace it? At first I thought it was not original, but I read somewhere else that someone else found this in his 41-296. Photo attached.

Any suggestions would be greatly appreciated. I am not an expert tech by any means, so forgive me if I've left out any important points.

Thanks
Brian


RE: Philco 41-296 Troubles - jerryhawthorne - 04-03-2013

Welcome Brian. Have you tested the antenna coil for resistance? Some voltage measurements on the Oscillator would be of value as well. Not certain if this radio has an RF amp, if so, another area to due some voltage measurements. I'm assuming you had the modulator turned on on your signal generator when you pumped your RF signal into the antenna. Don't laugh, I have done that before! I couldn't locate the schematic on N/A or I would have posted it here. Put the gimmic back on.
Jerry


RE: Philco 41-296 Troubles - w5ami - 04-04-2013

Jerry,

Thanks for the reply. I just woke up, so hope I can make sense..

I measured 49 volts on the Osc plate and 15v on the cathode, however that was with the switch in position 1 where the schematic shows it set, not the BC band. I also measured 85v on the plate of the 1st det. (RF amp/mixer). Yes, I did have the audio on with the signal gen. @ 1000 hz. I plan to re install the gimmic today and look again. I've got some cap legs lifted for testing I need to re-solder this morning before I turn it back on. I will recheck the voltages in the BC band position and a few other things and post back here. Thanks Again!

Brian


RE: Philco 41-296 Troubles - Radioroslyn - 04-04-2013

Hi Brian,
Long time no talk to! Welcome to the Phourm!
Take a listen with a portable radio at 455KC above the frequency on the Philco's dial for the osc. It sounds like it's not running.
Terry N3GTE


RE: Philco 41-296 Troubles - w5ami - 04-05-2013

Hello Terry! Good to hear from you.

Actually I heard a very strong signal at about 1270kcs on my 746 and had the Philco dial set near 1500kcs. It was coming from the Philco too, as it changed with a change on the philco dial.
Something is terribly off...

Brian