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Philco 40-140 Field Coil Replacement - Printable Version

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RE: Philco 40-140 Field Coil Replacement - radiola - 10-20-2012

Thanks again. It's playing great, and with the price of new standard variacs down, I hardly ever plug in these oldies without one--especially the ones with transformers. I run at a constant 108 volts for safety. ciao !!!

RE: Philco 40-140 Field Coil Replacement - radiola - 01-31-2013

Hopefully this thread still has some life. After replacing the field coil with the resistor and installing a 4'' permanent magnet speaker, I was not happy with the cheap sound, so recently I changed to a 6'' speaker. The set picked up hum when I did that, so I had to increase the size of the second power cap from 4 uf to 16 uf before the hum left. I need to know if that is safe or not. Would the transformer get hotter? Seems to. Thanks !!!

RE: Philco 40-140 Field Coil Replacement - Ron Ramirez - 01-31-2013

It shouldn't hurt anything to increase the value of the output filter cap. The transformer should not run hotter.

The extra hum was probably there all along since you did the conversion to a PM speaker; the 4 inch speaker, most likely, did not have the frequency response on the low end so that you heard it. The 6 incher obviously has a wider frequency response, so you started hearing the hum when you installed it. If the 16 uF output filter reduced the hum to an acceptable level, then you have done all you can.

RE: Philco 40-140 Field Coil Replacement - radiola - 01-31-2013

Ron, would the 16 uf cause the transformer to overheat? It does seem to be running a little warmer. I don't want to burn out a transformer for want of less hum. What happens inside the radio when you increase that capacitor? Thanks !!!

RE: Philco 40-140 Field Coil Replacement - Ron Ramirez - 02-01-2013

As I said, the transformer should not run hotter with the larger cap. If it does, then something is either drawing more current than it should, or else the transformer was already marginal (that is, possibly damaged) from old, partially shorted electrolytics and continued operation in that condition.

RE: Philco 40-140 Field Coil Replacement - radiola - 02-01-2013

The transformer is not running overly hot. I think the difference is, on the last check the chassis was outside the case. This model does have a back on it, and there are a few tubes close to the transformer to increase the heat. Anyway, it's all good and I appreciate your responses.