[captainclock1988]

Hello everyone a couple of years ago someone gave me a 1941 Vintage GE L-640 along with a 1941 Fada 176 for taking a look at a Philco 37-116 for him (which I tried to repair for him but didn't have much luck as it was more complicated than I could handle at the time as I didn't have much experience working on those kinds of radios at the time) and the Fada I was able to get going but the GE L-640 I have yet to attempt to get going because when I looked it up online I noticed that my example was modified and missing parts and I would like to try and see if I could get it going but looking at the schematic it seems that the modifications on mine are pretty extreme and are mostly in the antenna system area and also its missing its back cover which contained the antenna loop for the AM Band which is where one of the modifications was done, they had modified the chassis so that it could use a juryrigged "loop antenna" that was wired to the old loop antenna wire connections on the back of the radio through an adjustable coil and then wired to a small length of wire that they thumb tacked around the perimeter of the rear of the cabinet.

Also the dial string came loose (it didn't break just came loose) and I don't have access to a dial stringing diagram for this radio as the Riders didn't include one in the service manual for this radio.

Also the original speaker and output transformer is missing and I don't know where to get one except from a junker chassis which I haven't been able to find another one of these radios fullly intact on ebay for a decent price in a while especially not one that was being sold as a parts unit.

This radio had an old Utah Speaker in it but no output transformer attached to it or wired into the chassis anywhere they had the speaker wired directly to the output tube from the way it looked (at least that's what I could see anyways from underneath the chassis).

The cabinet is still in decent shape yet and the speaker grille cloth had beed "replaced" by someone in its past (the original grille cloth was still intact and in good shape yet just a little dirty under the "replacement" grille cloth which I'm going to see if I can clean it up and make it look like new again).

Also from what I could see from underneath the chassis, besides the antenna modifications the chassis looks largerly untouched underneath, with all original components intact yet, except for a modern power cord that was wired into the radio.


Any help and information would be appreciated, including parts if anyone has any available for this particular model.

Thanks,

Levi

[captainclock1988]

Does anyone have any information about this radio?

[RodB]

Here is the dial stringing diagram complements of radiomuseum.org:

GE L-640 DialString.pdf Size: 206.89 KB  Downloads: 222

On the OT & speaker you can get the plate impedance of the audio output tube and find a universal transformer with a primary impedance close to the tube.  That should match to a 3.2 ohm speaker. Don't have any answers for the antenna.  If you wait for a junker chassis you will probably wait a long time and then you may have competition.  Best thing to do is get it running now and buy the junker if it comes along.

Rod

[Eliot Ness]

Here's the output stage in case anyone has what you need or more suggestions:

   

[Radioroslyn]

> transformer with a primary impedance close to the tube.
Something around 5-7K is good. An AA5 transformer is too low as it's around 2K.

[captainclock1988]

OK, thanks I got the dial string taken care of now, I think that the speaker I had, may have been the original speaker after all because it said it was a 3.2 Ohm speaker, unfortunately the wiring harness on it (the part where the voice coil wires wire to) was broken so it was no longer usable also I think maybe it does actually have an output transformer, as i was looking at the wiring coming from the chassis and I think the output transformer is under the chassis rather than on the speaker like I though it should of been, thankfully its a permant magnet speaker so it shouldn't be too hard to locate a replacement speaker for the unit, I'll just see if I can find something on AES (Antique Electronic Supply) and go from there.

I did find a back cover for this radio on fleabay for $5 but it was missing its loop antenna so I think maybe I could see if I could find something over at AES (I think they sell some old style loop antennas there that are reproductions) that I could tack onto the back of the cover that I saw for sale on fleabay.

and then recap the unit and go from there.

[captainclock1988]

According to the schematic it looks like one side of the speaker/output transformer was grounded to the chassis which means that the speaker would of been attached to the chassis originally it looks like (unless thats an older version of my radio), which doesn't make sense because the way my radio cabinet was made the speaker was made to be attached to the cabinet not the chassis, and the output transformer wires (or at least what I'm assuming is the output transformer wires anyways) there are two wires coming from the output transformer as opposed to just one if it were actually a case of the speaker and output transformer being grounded to the chassis like in my Westinghouse 182.

[Radioroslyn]

<According to the schematic it looks like one side of the speaker/output transformer was grounded>

Don't think it matters much. Should work fine either way with one leg ground of the secondary or not. Just make sure that you do not ground anything directly on the primary side of the output transformer.[Image: https://philcoradio.com/phorum/images/sm...n_evil.gif]

[captainclock1988]

I double checked underneath the chassis and sure enough there is an output transformer there the thing that I was thinking was the output transformer but wasn't sure, was indeed the output transformer as the wires coming up fromt the bottom to the top of the chassis went to the output transformer, what's weird is that off the positive side of the terminal strip where the output transformer and the speaker wires attach to there was a small black wire soldered to it that led to the outside of the chassis and that wire isn't on the schematic, any ideas as to what that wire might be? 

Also does anyone have a spare 5" 3.2 ohm Permanent Magnet type speaker that they could send me for this radio? I've looked online and and I can't find anything, not even on ebay, or could a 4 ohm speaker work there as well? If so I might have some better luck finding something.

[RodB]

The black wire was probably for a second speaker external to the chassis. A 4 ohm speaker should work fine, whatever power is lost in the mismatch can be compensated for by adding a 4.7mfd, 16 volt ecap to the audio output tube cathode resistor or turn up the volume.

[captainclock1988]

Rod,

Would the speaker in the link below work in this application? This is assuming that the original speaker was a full-range speaker to begin with.

5" 4 Ohm Full Range Speaker

Also would that aforementioned 4.7 MFD 16V Electrolytic Cap be polarized or non-polarized, and could you mark on the schematic where that capacitor would go?

Thanks!

Levi

[Radioroslyn]

Spkr would be ok if it will clear the chassis. The ecap would be polarized and the + would go to pin 8 of the tube - to the chassis

[captainclock1988]

Terry, I'm not too concerned about whether or not it would clear the chassis as it just mounts to the speaker grille with 2 speaker mounting studs and nuts and the chassis sits back away from the speaker grille about 2 inches or so.

[RodB]

These are new speakers from Parts Express and you have to be aware of the mounting holes matching your mounting studs. A new 5" speaker is not the same size as the old 5".

[captainclock1988]

Hi Rob, I'm aware that the new PM Speakers aren't the same as the old PM speakers but when the old style PM speakers are far and few between then the new style ones are all you have left to fall on.