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Philco 42-123 - Printable Version

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Philco 42-123 - texan george - 10-01-2021

Trying to get this critter working but have a few problems. The audio transformer has a open on one side of the output p/n 32-8152. I don't have all the specs on it other than the schematic shows 1100 ohms to the tap and 900 ohms to the tap. Does anyone know of a replacement that would work. Any help at all would be most appreciated. Thanks,
George

(edited by admin)

RE: Philco 42-123 - admin - 10-01-2021

Please place an ad in Wanted Ads for the 2nd IF transformer you seek. Wanted ads are not allowed in the regular forums.

RE: Philco 42-123 - morzh - 10-01-2021

For the audio output try Hammond 125 series. Size up according to the power (they are all the same turn-wise and impedance-matching-wise) and then match to the tubes and the load.

RE: Philco 42-123 - Radioroslyn - 10-01-2021

Hi George and welcome,
What you are looking for is on that has a 50K primary center tapped and a secondary rated @ 3 or 4 ohms. Max current is very low about 10ma.

https://philcoradio.com/library/download/service%20info/yearbooks/1942/split/Part19-Philco%201942%20RMS%20Year%20Book.pdf

Tube data:
https://frank.pocnet.net/sheets/127/1/1LA4.pdf

GL

RE: Philco 42-123 - morzh - 10-01-2021

Terry


The 125 has 27K impedance for 4 ohm when connected to 4-5.
2-3 and 1-2 are more or less double the impedance vs 4-5.
Why not attempt then to connect 4 ohms to those 2-3 o 1-2? This will get you in the vicinity of 50K @ 4 ohms.

RE: Philco 42-123 - Radioroslyn - 10-02-2021

As per Mike's advise here's a link to the transformer he's suggesting. 125A Hammond Manufacturing | Transformers | DigiKey

RE: Philco 42-123 - MrFixr55 - 10-02-2021

Hi George,

The Zenith 8G005 also has a push-pull output but uses 1LB4 tubes. You may be able to convert to 1LB4s (Same electronically as 1Q5s but will have to modify the circuit for cathode resistance to maintain correct grid bias.

I am not a fan of junking a historical radio but someone may have already done so and the transformer and speaker may be available. Specs for both tubes can be found on the internet. Check Ryders, nostalgia Air, etc. for the schematics for both radios.

RE: Philco 42-123 - texan george - 10-02-2021

Thank yall for your responses, I will order one and let you know how it turns out. The transformer connects to 2 1LA4 tubes. Thanks for your input. To the administrator, thanks and I will put that in the wanted section.
George

RE: Philco 42-123 - texan george - 10-04-2021

yall have been helpful, now I need some more help on this transformer. I took the old one out and on one side 2 wires to Pin 2 (plate) of both 1LA4's, 1 wire center tap went to pin 3(G2) of the 1LA4's. Other side 1 wire went to the plug in for the speaker. No other wires. I am confused by this and hope someone can clarify how to hook up the replacement.
Thanks, George

RE: Philco 42-123 - Radioroslyn - 10-04-2021

One of the plates is connected to the blue wire the other to the brown. Red wire is the hv feed which is connected to the screen grid. On the secondary if you look at the old transformer I'll bet that one of the wires is solder to the frame. The other wire goes the speaker plug.     
Mike sez to try either 1 and 2 or 2 and 3 to connect to the speaker. Try both and see which sounds the best.

RE: Philco 42-123 - texan george - 10-05-2021

Your correct on the old transformer, I didnt see that. Thanks alot for your help and when the new one gets here we will see how it goes.
George

RE: Philco 42-123 - texan george - 10-10-2021

Sorry for taking so long to update. Lots of other stuff going on. Got the transformer and hooked up and powered up and let some smoke out. Found a few issues with bad solder joints, am going thru everything rechecking. One more question, it is missing the 2nd IF. took one out of old GE that had SMD, took the caps out and put a 100pF on secondary to try it out. According to the schematic, the original doesnt show a cap on the primary do I need to have one. Not a rush on that until I get the bad work redone.
Thanks,
George

RE: Philco 42-123 - Radioroslyn - 10-10-2021

I would use both 100mmf caps as that's what the transformer requires to resonate the coils at 455kc.

RE: Philco 42-123 - radiorich - 10-10-2021

hello George,
it looks like this set has really gave you some challenges anyway as Terry said 100mmf per side I also seen 120mmf .
Let us know how it is going when you get chance and as with the rest of us working and family comes first then radios .

Sincerely Richard

RE: Philco 42-123 - texan george - 10-10-2021

Thanks to Radioroslyn and Radiorich for your response and help. Going back thru each wire and double checking.
George