The PHILCO Phorum
41-240 Power Transformer - Printable Version

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41-240 Power Transformer - ccbaker13 - 10-23-2016

I picked a 41-240 and it needs a power transformer, it seems to be melting inside. I am new to this. I'm wondering if it is worth trying to buy a replacement one. I wouldn't know where to get one.

RE: 41-240 Power Transformer - Kenneth F. Besso Jr. - 10-23-2016

may not need one,,,,,check everything out ,,tubes ,,,,FIRST,,resistors,,and any and all capacitors,,,don't continue to plug it in,,,,,

RE: 41-240 Power Transformer - ccbaker13 - 10-23-2016

Well there is smoke coming from the transformer

RE: 41-240 Power Transformer - Nathan Slingerland - 10-23-2016

A smoking transformer could mean that something else in the circuit (outside of the transformer) is shorted and drawing too much current - causing a transformer winding to overheat. It's possible that the transformer is still good (hopefully it wasn't overheating for too long) - but you must at the very least check out the other components first.

If there is a problem further down the line then you'll only end up with a smoking replacement transformer. Icon_smile

RE: 41-240 Power Transformer - klondike98 - 10-23-2016

Kenneth is right.  Unless its been serviced recently the electrolytic caps, paper caps and some resistors will need replacement before you power it up again.

You can find a free schematic here: http://www.nostalgiaair.org/pagesbymodel/402/M0013402.pdf

and a clearer one here: http://www.audiophool.com/Philco.html  (you need a djvu reader for this one)

or a very clear one from Chuck for a few bucks: http://www.philcorepairbench.com/schematics.htm

The rubber wiring in this model will likely be bad and need replacement see: http://www.philcoradio.com/phorum/showthread.php?tid=14959

Caps at #52 should be Y2 safety caps, See: http://www.justradios.com/safetytips.html

The power transformer can be checked to some extent by checking the windings for their resistance (radio should be unplugged).  In the schematic below you see the power transformer.  If you place your ohm meter leads on the rectifier plate sockets (take the tube out) you should see something around 620 ohms.  Keep one lead on one of the plate sockets and place the other on the chassis.  You should see an open circuit (infinite resistance). If you see that, the secondary HV windings are good and there is no short to the chassis.  Similarly, you can check the primary windings by putting the ohm meter leads on the plug (with the set on-off switch in the on position).  You should see something around 13 ohms.  The filament secondary windings can be checked in a similar fashion although that will appear almost as a dead short since its resistance is only 0.2 ohms.  If these measurements all look good it could have been a short someplace else in the radio caused the power xformer to heat up.  They can have some wax/tar melt out and still function but its best to figure out why that happened.  Others on the Phorum are much better trouble shooters than I am but this is a pretty basic first look.  

[Image: https://dl.dropboxusercontent.com/u/54621529/41-240xformer.jpg]

RE: 41-240 Power Transformer - Radioroslyn - 10-23-2016

I'd pull the 7Y4. Turn it on. Does the pilot lamp light? Is it's brightness correct, not dim? Check rubber filament wiring for shorts. If you leave it on for 5 or 10min does the transformer smoke or get hot to the touch? Has the transformer lost wax out of the bottom and smell burnt. Measure the HV and filament winding for proper voltage without the voltage fluctuation.

If it has any of these issues I'd look for a new one.

RE: 41-240 Power Transformer - ccbaker13 - 10-24-2016

Thanks everyone for the tips. I'll check these things out tonight

RE: 41-240 Power Transformer - Kenneth F. Besso Jr. - 10-24-2016

GGGreat,,now we are getting somewhere,,,,,got lots of checking to do,,,Cheers,,hope all goes well

RE: 41-240 Power Transformer - ccbaker13 - 10-24-2016

Well I looked more carefully tonight and the piece the band switch contacts are mounted on is broken into pieces. There was no contact being made by the switch. I don't think I'm going to bother with this radio. I didn't pay anything for it.