The PHILCO Phorum
41-250 Restoration - Printable Version

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RE: 41-250 resistor size - Ron Ramirez - 08-09-2023

Bridkarl,

That Collins receiver, behind your 41-255 chassis...is that a 51J-x or an R-388/URR? Whichever it is, I like it Icon_thumbup

And what is the receiver (transceiver?) sitting on top of the Hallicrafters just left of center in the photo you posted in post #41, page 3, this thread?

bridkarl Wrote:My plan is to work through the rest so when I retire I just quit repairing and have a vintage radio room where I just sit and listen all day

I had similar plans at one time - I was going to start working through my remaining radios when I retired, when I would finally have the time to do so. Unfortunately, cancer sort of changed those plans. Forced into retirement a few years early as a result (I'm now 63), I have sold off or given away much of my collection although several still remain. As long as I am able, I hope to continue working more on many of the sets which remain - it keeps my mind occupied and off my troubles for the most part.

These past few years, I've turned away from Philco and have branched out into a few other radio makes to experience some of what I have missed out on over the past few decades.

I've been in the hobby since 1974 - 50 years next summer. And like John (MrFixr), I never was a ham either.

RE: 41-250 resistor size - bridkarl - 08-09-2023

That’s a 51-J3. 1952 I think. Interesting I bought that as broken - turns out the previous owner didn’t check the speaker they were using. The radio works fine.
I have it connected to a Hallicrafters PM-23.


That’s a Tempo 2020 on top of the Hallicrafters SX-24 on the right - that’s a 1945 Hallicrafters s41-G on top of the HT-37. The S41-G looked like it had been stored underwater when I got it.

RE: 41-250 resistor size - Radioroslyn - 08-10-2023

I had a 51J4 for a long time and just sold it to a member here a yr or so ago. Used it for my main receiver in my ham station. I did one useful and simple mod to it to improve it's performance. That was to increase the value of the bfo coupling cap feeding the IF. The original is very small on the order of 5 or 10 mmfd. Increased it to about 50mmfd. This improves the signal handling ability when the bfo is used. Doesn't overload nearly as bad as before on ssb reception. It's not as good as converting the bfo tube circuit to a product detector but it's an improve over the stock.

I see you have the Heathkit transmitter that the osc puts out more than the final amp...[Image: https://philcoradio.com/phorum/images/smilies/icon_e_surprised.gif]

de N3GTE

RE: 41-250 resistor size - bridkarl - 08-10-2023

Here’s the cap arrangement for the 41-255.  There’s a 16/8 mfd dual cap rated at 475 on the chassis side. That’s a 12mfd cap in the middle. I’ve sketched out roughly the wiring so you can see where this goes. 

The parts are listed in the 1949 Philco catalog p.87

RE: 41-250 resistor size - MrFixr55 - 08-10-2023

When compared to the schematic, this is correct

RE: 41-250 resistor size - bridkarl - 08-10-2023

Thanks. I find a picture is helpful sometimes in making sense of a schematic. I intend to replace that 15k resistor. I also picked up some heat shrink wrap for some of those wires. Seems to be going along in the right direction.
I have some work stuff starting so it may be a few days until I get back to this. Thanks everyone.

RE: 41-250 Now fixed!!! - bridkarl - 08-14-2023

Thanks to the good advice here my 41-250 now works. Sounds good on all bands AND the dial lights now work. Haven’t found a proper Philco lamp holder but the one I have wired in seems to work ok. 

Only drawing about .38 amps at 110 volts so that’s good. 


What’s left to do is new caps for the bake light block, a fuse, and a new power cord. After that I’ll do the 41-255 - this was working fine so I hope getting that working again won’t be a huge deal.

RE: 41-250 Restoration - admin - 08-16-2023

Your bakelite block thread was merged with your 41-250 restoration thread as it is on the same subject radio, per Phorum Rules.

Thanks.

RE: 41-250 Restoration - Ron Ramirez - 08-16-2023

It's actually "O", not "0" (zero). The "O" indicates the use of high temperature wax for potting the block. Otherwise, 3903-DG and 3903-ODG are the same part, using the same .01 uF capacitors inside.

On the blocks themselves, they may be embossed "3903-ODG" or stamped "3903ODG". Again, same part.

Incidentally, these bakelite blocks which have terminals connected across the incoming AC line should always be restuffed with X1/Y2 safety capacitors.

RE: 41-250 Restoration - bridkarl - 08-16-2023

The bake light block shattered in the process of cleaning it out. Anyone have a picture of the preferred location/installation for using a terminal strip in place of that?

In the meanwhile I salvaged the other bakelight block from the 41-255 - which I need to go through anyway - cleaned it out without breaking it, put in two .01 Y safety caps, a 1 amp fuse under the chassis and a better power cord. I also used some heat shrink to cover and reinforce these connections. 

You can see from the pic that someone had just wired in some caps on top. No good. Also a pic of what the old caps looked like. That’s all cleaned up. 

So aside from maybe doing an alignment and doing some cosmetic stuff like installing new buttons etc. I think this radio is done. I can’t think of anything else I need to do - I didn’t install a three prong grounded plug. Any further suggestions?

RE: 41-250 Restoration - klondike98 - 08-17-2023

If you haven't seen it, we have a tutorial for removing the guts of the bakelite blocks in our library. See: https://philcoradio.com/library/index.php/shop-talk/techniques/bakelite-capacitor-rebuild-without-desoldering/

While the tutorial leaves the block connected to the chassis, I almost always remove the block first and then go through the lead snipping, heating and pushing the tar block out process. For me I just find it easier. A hair dryer will work as well as a heat gun. It does not need to get too hot before the tar softens and you will be able to slide it out. then a little clean up with mineral spirits if you like them clean inside.

RE: 41-250 Restoration - bridkarl - 08-17-2023

I tried to follow that. The block still cracked - it is an 80 year old piece of plastic after all. Stress fractures in materials happen.

The other one went well although I did have to drill out the eyelites with a 5/16 inch drill. I found the Y caps I got for this had short leads - got it all done but next time I’ll add length. It’s working well now - so no shorts - I’ve added a fuse anyway. 
I’d like to find an empty bakelight block - having this on a terminal strip near the chassis makes me nervous plus it’s just not authentic.

RE: 41-250 Restoration - Ron Ramirez - 08-17-2023

I get it. It doesn't help that Philco's AC line bypass bakelite blocks they made after 1938-39 were potted with a different material which is nearly as hard as a rock! Older bakelite blocks use a type of wax which melts easily, allowing the older blocks to be easily un-potted and then restuffed as Bob (klondike) mentioned.

RE: 41-250 Restoration - bridkarl - 08-17-2023

Like I said I did try to follow the process as outlined. Sort of worked but I still had to carefully dig some of it out - it was hard as a rock as you say. Drilling out the eyelets seemed to me the way to not put extra stress on the block.

RE: 41-250 Restoration - Ron Ramirez - 08-17-2023

You don't want to drill out the eyelets - the eyelets are what hold the solder terminals in place on the block.