Philco 42-350

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Philco 42-350

Post by Big Toe on Tue Sep 24, 2013 3:06 pm

I bought an old Philco 42-350. It does not work, but the transformer does smoke after being plugged in for 30 seconds or so....I guess that's something. The stamp on the side of the transformer is unreadable, so I was wondering if anyone might have the part number or value. It has 6 wires coming from it. I live in Sevierville TN and Ten Tec is having their once a year hamfest this Friday and hoped to get some parts and tubes there. Thanks

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Re: Philco 42-350

Post by scottb on Tue Sep 24, 2013 3:23 pm

The radio will need to have the filter and paper capacitors replaced along with any resisters that have changed value. That is most likely what is causing your transformer to smoke. I hope the transformer is still OK as that would be expensive to replace.
You might want to make a diagram of tube placement, then pull all of the tubes, then turn on the radio to see if the transformer gets hot. If it stays cool, it is then time to obtain schematics and test the voltages to see if they are in spec.
Also I forgot, you probably should use a dim bulb tester, basically a light bulb in series with the power going to your radio. I have to get back to work, but I am sure if you do a search on dim bulb tester, you will find out how to build one.

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Re: Philco 42-350

Post by Bill Cahill on Tue Sep 24, 2013 3:25 pm

Don't plug it in again! The radio electrolytics have shorted out, and, ruinned the power transformer... It may be difficult to find a replacement transformer for this set. Radios, tv's, anything, should NEVER be plugged in until they have  been properly restored...
This repair will be costly now, due to the dammaged power transformer.
Other than that, welcome to the forums.

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Re: Philco 42-350

Post by Big Toe on Tue Sep 24, 2013 4:49 pm

Thank you all for answering so quickly. From what you all are telling me, it may be a boat anchor. I may take it to the hamfest and see if someone there might like to look at it, as I think any repairs might be above my pay grade. I will stick to refinishing the cabinet.

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Re: Philco 42-350

Post by 75X11 on Tue Sep 24, 2013 5:36 pm

They are a nice looking set.  They are a mighty difficult set to tackle as a first effort.  in addition to the capacitors to be replaced, much of the wiring had rubber insulation that has in all probability has turned into a stiff, crumbly material and is subject to shorts among the newly naked wiring.  That may be one to look at on display for awhile until you do some simpler units.  Or you may find someone at the fest who would want to repair and restore your set for a reasonable price.
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Re: Philco 42-350

Post by Bill Cahill on Tue Sep 24, 2013 8:36 pm

I agree, but, I'm still afraid power transformer is toast. Don't let it stop you from learning to restore. You need to start simpler, and, remember.
DO NOT plug it in until you are absolutely sure of condition. Especially replacing paper caps, end, electrolytics first.

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Re: Philco 42-350

Post by Wildcat445 on Tue Sep 24, 2013 10:07 pm

Welcome to TRF. Thare are lots of helpful people here to help you.

Regards

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Philco 42-350 power transformer part number

Post by dan88king on Sat Oct 19, 2013 8:20 pm

Rider's parts identification page lists this power transformer as Philco P.N. 32-8183, for 115 V, 60 cycles. There is also a power transformer for 25cycles, and you don't want that one. It will overheat badly on 60 cycles. The rider's service data pages are 14-28. 14-38, 14-39, and 14-40.
I would think your best bet is an exact replacement. This transformer is an odd one, in my experience. Most use 5.0 volts AC for the rectifier heater winding, but this one, for the 7Y4 which has an indirectly heated cathode, uses 6.3 VAC and also powers three dial lamps. I figured out the 6.3 volt transformer windings (2) current requirements: 6.3 VAC at 2.5 amps for all the tubes except the 7Y4. 6.3 VAC at 2.0 amps for the 7Y4rectifier's heater and the three dial lamps, at a typical draw of .350 amps each, lamp type 47 is typical. Now for the higher voltage center-tapped winding: Rider's says the B-plus voltage at the 7Y4 cathode, pin 7 in the bottom view of the socket, is supposed to be 275 volts DC. I have run into serious trouble with a power transformer substitution where the B-plus voltage turned out to be too high after installation. You can pull it down some by adding a large (physical size) bleeder power resistor from B-plus to B-minus, but I quickly ran into a heat problem under the chassis, and the B-plus voltage wasn't as stable as I would have liked. So if you can get hold of a junk 42-350, that would work best. From the high voltage winding's center-tap to each end of the winding should measure about the same. Offhand, I can't remember how to calculate this, and it probably would depend also on the B-plus current drawn by all the tubes. I've seen specs at 300-0-300 VAC, 350-0-350 VAC, and higher. A substitute transformer of course has to fit on the chassis physically and come close to matching the available space and mounting holes, unless you want to drill new ones. I put one in an 11-tube Philco 41-395 years ago, not the correct Philco part number, and I had to use two extra steel mounting brackets on the back side, and it stuck out from the back of the chassis somewhat, but electrically it worked great. I hope this helps.

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Philco 42-350. XXL and XXFM tubve substitutions

Post by dan88king on Sat Oct 19, 2013 8:25 pm

I forgot to add this note: The XXL loktal tube can be replaced with a 7A4, a direct substitute. The XXFM is the same as a 7X7. They may already have been subisituted. It was commonplace.

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