The PHILCO Phorum
37-640 bandswitch ? - Printable Version

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+--- Thread: 37-640 bandswitch ? (/showthread.php?tid=25558)

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37-640 bandswitch ? - georgetownjohn - 01-18-2025

Hello Phorum Members:  I am attepting to reassemble my 37-640 during restoration but have encountered a problem reinstalling the bandswitch.  I have inserted the shaft of the bandswitch with the flatside up so that it will be in the BC position but it seems to get stopped at about the last wafer position and will not go in all the way.  Can anyone offer any suggestions of what I might try ar what the problem is.  Thanks--John

RE: 37-640 bandswitch ? - RodB - 01-18-2025

Maybe a photo would help.

RE: 37-640 bandswitch ? - morzh - 01-18-2025

Was about to ask what Rod's asked.

Let's live nothing to the imagination, so to speak Icon_lol

RE: 37-640 bandswitch ? - georgetownjohn - 01-18-2025

Rodb and Morzh, thanks for the reply.  Attached are 2 photoss that I hope will help with my question.  Thanks again, John

RE: 37-640 bandswitch ? - morzh - 01-18-2025

I will be very honest, I do not know if this even matters.

https://philcoradio.com/phorum/showthread.php?tid=20907

I found this thread. The chassis seems as "unmolested" as it gets.
Seems, the blurred it is, the flat side is up.

RE: 37-640 bandswitch--Maybe big trouble? - georgetownjohn - 01-18-2025

Thanks for the replies.  I finally was able to wiggle the shaft of the bandswitch and it slid into place, however while I had the chassis tipped up on its side, a strange looking piece fell out!!!!!  I have included 3 photos of the piece.  Does anyone know what this is and will my radio ever work again?--John

RE: 37-640 bandswitch ? - morzh - 01-18-2025

1. Yes, I think I know what it is. It is the piece that goes over the shaft and rotates, switching between the contacts.
2. Try to get the photos a bit sharper. It actually hurts physically (for some people, me in particular) to look at blurried photos.

RE: 37-640 bandswitch ? - RodB - 01-18-2025

I'll be working on a 38-4 next weekend. If you need more help I will have a close look at the switch or any other issue.

RE: 37-640 bandswitch ? - georgetownjohn - 01-19-2025

Thanks for the replies.  Hopefully, when RODB take his 38 model apart, he will be able to ID the part.   I will try to get better photos but that may be the best my old tablet can do for close ups.  If this part turns out to be part of the RF bandswitch, what is the chance of finding a replacement or is it not worth it and just put the radio in the trash---John

RE: 37-640 bandswitch ? - morzh - 01-19-2025

Good question about the chances.
But I see that the "D" is still preserved; that gives me hope it could be somehow re-installed (wonder why it fell at all).

As for the tablet cams...use the phone. Their rear cams (that is, if you have a cell phone; some folks have ideological objection to them, which I fully understand) today are amazing.
And then just drop the pic using your phone as the tablet to access the Phorum. I do that sometimes.

37-640 part IDd - georgetownjohn - 01-19-2025

OK, I have discovered that the part is one of the roatating contacts for the bandswitch. It has 4 different orientations for placement and only one is correct for proper function.---John

RE: 37-640 bandswitch ? - Greg - 01-19-2025

I think that part is meant to be a permanent part of the switch.

I took a look at one I had lying around. The wafer with the stationary contacts appears to have "fingers" holding the "rotor" in place. I marked one in the picture below (you can see one):
   

Maybe you damaged one or more fingers and it got loose? I kind of thought the engaged contacts would have held it in place (would think there are some for each position).

I suspect it would be possible to replace it and the contacts would hold it in place long enough to get the shaft put in place. You have to figure out how to not put it in "backwards". Even if the fingers are busted, the contacts may be enough to keep it from "wandering" on the shaft? Just guessing...

Is that the last one of the lot? If so, maybe that's why the shaft finally went in.

RE: 37-640 bandswitch saga continues? - georgetownjohn - 01-19-2025

Greg, thanks for the reply.  Yes, it was the last one so you may be correct that it was why the shaft finally went in the last couple of inches.  Your photo may give me some clue as to wether I can attempt to reinstall it.  I am still not sure what to do.  Thanks again, John

RE: 37-640 bandswitch ? continued - georgetownjohn - 01-19-2025

Greg, I forgot to ask one important question.  Will any part of the radio work with this part gone or might it just impact one band?  Thanks again--John

RE: 37-640 bandswitch ? - Greg - 01-20-2025

I suppose that if every thing down stream from the antenna transformers is OK, the radio should “work”.

If, you clip a wire (small antenna) on to the RF tube grid cap you should get some reception. You are bypassing the antenna transformers. See the schematic and you’ll see what I mean. It will work better with them (transformers) but ought to work to some degree without them. What could go wrong Icon_biggrin ?

Others may have suggestions too.