Philco 37-640 - Printable Version
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RE: Philco 37-640 - morzh - 02-13-2020
Looks violet...partly.
Its easy to ohm it out. Why guess. Even in circuit measurements give an idea where the value is.
85K obviously closer to 70k. Purple and orange make 70K.
RE: Philco 37-640 - mikethedruid - 02-13-2020
Yeah, Mike, figured that out a while ago. Read on, and see what the latest is.
RE: Philco 37-640 - mikethedruid - 02-13-2020
Well, I couldn't leave well enough alone, so I rang out the transformer and the field coil. The field coil and the transformer secondary are OK, but the primary is open on both sides. I am just going to see if I can fins another speaker.
RE: Philco 37-640 - mikethedruid - 02-18-2020
Since nobody seems to have a K-34 speaker that they wish to part with, I am going to do what I can to use what I have. I ordered an output transformer for push-pull, the primary impedance match may end up off with the 1.1ohm voice coil, but it is the best I can do, considering. This is what I ended up ordering https://www.tubesandmore.com/products/transformer-output-8-w . Today I fitted the new cone. Fortunately I had one, right size, basically. I did have to enlarge the center hole by about 1/16 inch all around, and take about 1/16 inch from the outer edges. The slope of the cone is perfect, as if it was made for this speaker. I glued up the voice coil / spider piece to the cone, and centered it in the basket and magnet section, but did not glue it, just screwed in the spider again, and let the Goop dry. This evening I removed it again, and replaced the wires to the voice coil. It was raining all day, and is supposed to rain more tomorrow, maybe even snow. As soon as the weather permits, I will drill out the big rivets holding the output transformer to the basket, and make a new mounting for the replacement transformer. Here are some pictures of the work so far:
[Image: https://66.media.tumblr.com/2a4d26aa56ef83de06df45ceda46b503/edef701c068137e7-d5/s1280x1920/7e03e4c9ccc831b38608d98e2ea4ee89e615dce1.jpg]
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RE: Philco 37-640 - Jake Blake - 02-18-2020
Hmmmmmm....Interesting tedious work. Nice Mike.
RE: Philco 37-640 - Nathan Slingerland - 02-18-2020
Nice work Mike!
I'd guess there simply aren't that many K-34 donor speakers out there. According to Ron's speaker spreadsheet the K-34 was used exclusively on the 37-640B:
https://philcoradio.com/library/index.php/parts/speakers/
And from the production data in the Gallery there were only 7,000 37-640B _and_ 37-641B (same cabinet) made.
https://philcoradio.com/gallery2/1937a/#Model_37-640B
RE: Philco 37-640 - mikethedruid - 02-19-2020
Yeah, Nathan, it's a fairly rare model. That was one of the reasons I bought it. If and when I finally get it working, it will be a nice addition to my collection.
RE: Philco 37-640 - morzh - 02-19-2020
Great job, Mike.
I could never bring myself to try to replace a cone or a voice coil.
RE: Philco 37-640 - mikethedruid - 02-20-2020
Mike, I didn't have to replace the voice coil, thank God. I am just replacing the cone, and transformer, and the leads from the transformer to the voice coil. If you have to replace the cone on one of the Philcos which use a spider attached to the voice coil, it is really not that bad a job. The spider makes the voice coil self centering. Just pre fit everything carefully before gluing it up. Then use a slower setting glue to glue the cone to the voice coil assembly. I have always used Goop. It dries into a vinyl rubber, and is slow drying, which allows one to make the little adjustments to the cone one may have to once the voice coil is inserted, and the whole thing is then inserted back into the basket, and the center screw of the spider installed. I let it dry over night, then take it back out before applying Goop around the edges of the basket to finally secure the cone, and then re-installing the center screw, and doing final adjustments to the edges of the cone. The most important thing is to get the right cone for the job, or adjusting what one ends up with, so that it works. You will remember my work on the RCA T8-18. Now THAT was a hair raising job that required some ingenuity on my part. This speaker is easy compared to that, except I wish I could get a transformer that matched impedance better.
RE: Philco 37-640 - rfeenstra - 02-20-2020
Send me your old one and I'll see if I can rewind it for you.
RE: Philco 37-640 - mikethedruid - 02-20-2020
Thanks for the offer rfeenstra. I'll definitely keep it in mind. First, I'll see how the one I just bought works. If it doesn't live up to expectations, I'm going to buy this: https://www.tubesandmore.com/sites/default/files/associated_files/p-t125-a-e.pdf It is a great universal push pull transformer, the PT-125E has an output impedance down to 1.5 ohms, which would match the voice coil well. and should do the job just fine; but, having already purchased the one I did, I'll try it first and see how it works. If neither work out, I may take you up on the offer.
RE: Philco 37-640 - mikethedruid - 02-22-2020
I have ordered that output transformer from AES, along with a lot of condensers, which brought my total up past the point where shipping is free. Now I have to wait until it arrives before I continue much with the speaker. Today I did cut a piece of fairly heavy gauge sheet metal to use in mounting a new terminal strip and the transformer to the speaker basket. Beside that, I rebuilt the lamp socket for the shadow meter. I had already rebuilt the one for the tuning dial. After that, I gave the chassis its very first test, to see if it had filament and lamp power, and.........
[Image: https://66.media.tumblr.com/6327fa66ec0551f53e0f392a05ef7986/21189df734af628f-1d/s1280x1920/853bbcec24958b546d67c342da40546cafd0fc73.jpg]
SUCCESS ! no smoke, no explosions, no crackling. Of course, there are not even any tubes installed yet, just the two lamp bulbs, but they are working fine in their rebuilt sockets. It's a good first sign. Once I finish the speaker, I can get on to REALLY testing things.
RE: Philco 37-640 - Jake Blake - 02-22-2020
"It's a good first sign."
Nice! I looooove dial lights!
They really make the antique radio! That's as far as I've gotten with the 610 also Mike.
RE: Philco 37-640 - rfeenstra - 02-22-2020
Love your work bench, Mike. Reminds me of mine! Stuff and tools everywhere with a small space for the project at hand. The only way to work!
RE: Philco 37-640 - mikethedruid - 03-06-2020
I finally have gotten all the various bits and pieces to finish the rebuild of the speaker. I made a mounting plate for the Hammond P-T125E output transformer. Today I finally got to put it all together. I used extra heat shrink over the fine wires that go to the voice coil where they have to pass through the little clip inside the basket. The leads from the hum bucker coil are a little long, and will be dressed later, after testing, when I have made sure they are not connected backwards. Here are pictures of the whole thing.
[Image: https://66.media.tumblr.com/b5464c384e0f212b553c3a1c567cdb64/a511347a21aac90c-18/s1280x1920/c0266fc85235a751c4e66995b9edb9ac01bd2de9.jpg]
[Image: https://66.media.tumblr.com/2628d7987c7e2187c559d14587da803d/a511347a21aac90c-61/s1280x1920/30ba68f023d384bb7b1e805b9e62a5199c158c8a.jpg]
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[Image: https://66.media.tumblr.com/d84ee68405c8f5368974020d9d2ec692/a511347a21aac90c-9c/s1280x1920/62b6156bbc86837f0851c21ff0aa04d2a8a7b61a.jpg]