The PHILCO Phorum

This thread will cover my electronic refurbishment of my recently acquired Philco 38-10. To see what the cabinet looks like look for my post about it in the March 2021 Finds and Losses thread. The cabinet is in amazing condition. The faux finish is virtually pristine! I am including one repeat picture from that thread which shows the back of the radio as I received it. There was a switch mounted back there...


At first I thought it might be a quickie replacement for the on-off switch, but I was wrong. Turns out it is a phono input added long ago, probably no later than the 1950s from the look of the condensers used.


I will certainly keep that input, since it forms a pert of the radio's history, and is also useful. I will actually re=stuff the condensers since they will be above the chassis this time and may be partially visible if someone looks from an angle. Beyond that, I pulled the chassis. The radio is mostly virgin. Beyond the phono input the only obvious repairs are the replacement of the filter condensers. These are also a long ago repair, one of them is labelled "Olson", and the other is labeled with just the initials G and a backwards L, which I don't recognize. Some of you, like me, will fondly remember the Olson Electronics catalogs.


So, that is all I have done so far. I'll get deeper into it tomorrow.

Last night I removed the old condensers from the phono input module, and baked them at about 200F in my oven until the wax had melted and I could pull out the guts. They were both .05MFD. I re-stuffed the original tubes with .047MFD 630V yellow poly caps. I sealed then ends with clear RTV since the ends really won't be that noticeable. I then left them sit over night to dry. Today I reinstalled them in the phono input. It looks pretty original, but will work like new, and the new caps are more than twice the 250V rating of the originals. Here's what it looks like now.


I also picked up a 2 foot piece of PVC water pipe and some flat silver Rustoleum spray paint. I am going to make reproduction electrolytics  to mount on top of the chassis in place of the two later replacement types which are presently there. This will free up some of the real estate in the chassis when I can remove the other replacement electrolytics which someone later installed inside the chassis when the dual section one above the chassis went bad.

Mike did you check to see which power transformer is installed in your set? Living in Florida one of the first things I check out with all the retires for other states you never know. Stay Safe David

David, it's a code 121, 115VAC 50-60 cycles. Dirt common variety, and will do just fine here as all my other ones do. My voltage is about 118V.

I spent today making the replica electrolytic cans for the 38-10. According to the parts list one, part 12, was a two part electrolytic 4MFD and 8 MFD. The highest voltage shown in the Philco literature is 375V. The old replacements were 450V. I used two 10MFD 450V condensers for replacements. I used a 20MFD 450V condenser for part 45. Here isw the process I used for making the replica electrolytic cans...



I used 1" PVC pipe from Home Depot. They sell it in 2 foot pieces so you don't have to buy a huge long piece.





I cut it into 3 pieces, two were 4 inches long, the other was less than an inch long.





I sanded the outside of the 4" pieces well, all over to give the outside some tooth for the paint to stick to later. I then cleaned the pieces well with lighter fluid on a clean paper towel to remove any grease or dust from the outside.





Next I took a piece of card stock, in this case cut from a Little Debbie Swiss Rolls box, and drew circles using the short piece of pipe for a guide.





I carefully cut out the circles cutting just outside the line drawn so that the diameter would be very, very close to, or a hair more than the inside of the tubes. I glued two circles together using 2 part epoxy for each top, and three pieces for each bottom. Make sure the circles are all perfectly lined up for each top and bottom. After several hours, when they were well dried and could be handled, I again used 2 part epoxy and glued the tops into the tubes.





I drilled 3 holes into one bottom, and 2 holes into the other for the leads from the condensers. I then assembled the interior components.





I ran the leads from the condensers through the holes in the bases, and glued the bases into the tubes using 2 part epoxy.





When they were well dried, I masked off the leads with newspaper, and then sprayed the tubes all over with satin finish silver Rustoleum paint.





Using my computer and printer I made labels to go on the condensers. When the paint had dried for several hours I glued the labels onto the finished replica electrolytics using 2 part epoxy.



And that is how I made replica electrolytic cans for my Philco 38-10. I hope this can be useful to others who end up having to replace the originals.

Good job.

Today I completed the work on the chassis, all paper condensers are replaced. The electrolytics are replaced with the ones I made for this radio. All resistors which were out of spec, or nearly out of spec have been replaced. The line input condensers in the bakelite block have been replaced with safety caps, a new line cord has been fitted and a new wiring loom to the speaker has been made and installed. Next will come attaching the speaker, then testing, and if all goes well, alignment.

Last night I connected the speaker to the new wiring harness I made for it, and gave the radio a test. The dial light didn't work, I removed it completely from the radio, de-soldered the wire where it connected to a tube socket inside, and rebuilt the socket. The rubber part inside had deteriorated badly and was stuck do one could not remove the bulb. I finally got the bulb base out after breaking the bulb itself. I made pseudo micarta board by gluing three thicknesses of card stock together with epoxy glue. When it was dry I drilled a little hole through the fake micarta, just big enough to pass the conductor of a new cloth covered 20 gauge wire. I passed that through the little hole, and made a little circle of the wire flat to the board. I then soldered the little circle quickly so as not to burn the board. I then carefully clipped away at the board surrounding the conductor until it was a circle just small enough to easily slip into the metal socket housing. Next I took some heat shrink and ran it right up the wire to the board and shrank it in place. I put back the spring on the wire, slipped the wire into the housing and drew it back, and inserted a new bulb. I connected the wire back to the terminal on the tube socket, and then tested the radio again. The bulb flashed and blew out ! Needless to say the air turned blue for a few minutes, being the old sailor that I am. I then removed the wire again and fired up the radio and checked the voltage. I was read 7 volts, not enough to blow a bulb like that, so I re-installed the wire and socket with a new bulb and tried it again. What do you know, it now worked fine!

After that I set about doing an alignment on the set. The IF went smoothly, it was very near perfect as it was. I then set about the rest of the alignment. The short wave went smoothly enough, but the broadcast band was a major pain! The instructions are NOT as good as they should be, in fact they turned out to be misleading. It took me hours last night, and then again this morning to get things good, but they are now, and frequencies match up at the top and bottom of the dial, and are coming through strong with my signal generator on the lowest output setting. Nest thing is to re-install the chassis into the cabinet and then test the radio on my outside antenna tonight.

On the outside antenna, when I first turn on the set I receive stations fine all up and down the broadcast band. WSM comes in strong at 650 as it should, but, after a little while the lower end of the band fades away. The upper end from about 1000KC on still comes in quite strong, with lots of stations, but below that reception faces quickly, and below about 800Kc the radio becomes deaf as a post. I pulled the chassis again, and rechecked the alignment over and over. I did notice it is still flukey even just trying to align it. I am going to replace some tubes because I am wondering if I have one that is going weak as it heats. Oddly, short wave seems much less affected than the broadcast band. I have checked and rechecked the connections, and I don't think they are the problem. If any of you have encountered the same sort of problem let me know, and tell me if you discovered the cause.

Well, the radio is back on the bench and out of the cabinet. I found one problem, a partial short in the wiring around the 6Q7 tube between the hot filament line and the plate ! The routed the wire around the plate terminal, and somehow it must have eventually worn through the insulation. I can see the blackening from the arcing. That would also explain why the dial lamp blew out, and the funky voltage on the filament line.Things still aren't right so I have more chasing down to do.

It's always something! Gilda Radner (and my Mom)

I have continued to eliminate things. Today I tested the windings on the two IF transformers, and I get reasonable readings on both primary and secondary on both transformers, so I can eliminate that. I replaced #16, the 10K 3 watt resistor with two 4.7K 3 watt resistors in series, but they now show signs of overheating at some point although they test OK as far as resistance still. I have ordered some 10K 10 Watt resistors to replace it.

NOTE TO ANY POOR SOUL WORKING ON A 38-10: Part no. 21, the 51K resistor, is INSIDE the IF transformer can. When you take readings for the secondary winding of the second IF transformer, they will always be the actual winding value, in this case about 8.2 ohms, PLUS the 51K resistor! This threw me, and I wondered if my transformer was bad, until I took it apart and saw the resistor inside, and measured across the actual windings, which were both good. I wondered if part no. 21 might be in there, and now I know. Note well anybody who works on these radios; if you get a weird reading on an IF transformer, look inside the can before you freak out. Philco may have hidden something inside. OH ! and that brown paper is held by a resin or wax that melts with heat. Just warm it up gently, and it will peel open, and then warm it back up to seal it back closed.

I have been hunting down the problems which sprang up with this 38-10. If I inject an audio signal at the grid of the 6F6 it comes booming in loud and clear. If I inject it at either the wiper of the volume pot, or the terminal fed from the 2nd IF transformer, I get a lower signal which can be controlled by the volume pot. I believe this means the audio signal is getting through the 6Q7 triode section. Between the side of C22 which is shown connected to the green wire and the high fed terminal of the volume pot, I read a bout 51K, which is what the schematic shows it should be.Here are two pictures of the schematic, the first the full schematic, the second a close up of the area being discussed...




I have checked C22 with my capacitance checker, which shows it well within tolerance, at least at low voltage. Yesterday I took apart the 2nd IF, removed the can to ring out the windings, and found R21 lurking inside. R21 checked out to be approximately correct for 51K. The windings also rang out a little less than 10 ohms, and seemed about right. I didn't check C23 or C24. I am getting no feed through of a modulated IF signal when I inject it at the antenna input, or even if I inject it at the green wire side of C22, or the other diode plate for that matter. It is not demodulating it and converting it to audio. I wonder, could the problem be with C22, C23, or C24? Any ideas? Yes, I have even swapped out the 6Q7G just to be sure it wasn't the tube. Any help or suggestions will be appreciated.

This evening I again took apart the can of the 2nd IF transformer. I didn't remember seeing any capacitors inside there, although at the time I was busy checking the winding continuity. Again. the windings were fine, the resistor R21 was fine; but, as I remembered, there were NO OTHER CAPACITORS in there besides the two variable caps on the top of the porcelain cap. There is a green and yellow wire attached to a lug on the top porcelain with the two variable caps, which I surmise should be the central grounding wire between caps 23 and 24, but there is NO SIGN of caps 23 or 24! I know the radio DID work when I first tested it, so it was working without these capacitors. What purpose do they serve? Why would they have been left out of my radio? Did Philco often make undocumented changes? This must be fairly early production because R11 was still a 70K resistor, and that was changed to a 40K later in production to improve oscillator production. (I have made the change) This is a very curious radio !