938A, Philips; Eindhoven Radio (Techniek Radio/TV)

door gspencer691 @, 04.06.2021, 21:51 (1069 dagen geleden)

10 years ago I bought this 938A, Philips; Eindhoven Radio only to find that it's output transformer is missing. I downloaded it schematics from the net and it's service manual which is completely in Dutch. I tried translating it on Google translate and still got no reference regarding what type of transformer this is. I am not a professional and I have no option except to try to watch videos on YouTube and try to fix it myself by removing and replacing. I joined this kind Group looking for some help. Two days ago a nice gentleman on another group responded to my post inquiries. Nevertheless I did not understand anything from What he told me. I was shy to tell him that I know nothing of what he was saying. Below I am attaching photos of the radio, schematics and Photos from the service manual regarding this part. I hope and appreciate if someone would tell me in plain English what type or name of the transformer I am supposed to buy.[image]
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938A, Philips; Eindhoven Radio

door hans @, Hoorn, 04.06.2021, 22:55 (1069 dagen geleden) @ gspencer691

Dear Gspencer,

Welcome to this forum.

Hopefully, you have managed to make out the output transformer in the circuit diagram. If, as yet, you have not, look for S19 and S20 in de top right corner. In the adjacent parts list this translates to part 25.510.39.0.

Problem solved? Hardly. Getting hold of this transformer is nigh impossible. However, the end stage of the 938A resembles the 834a's end stage, i.e. same output valve en transformer type. As it happens I have a loose 834a's loudspeaker with attached output transformer. I saved the set for a rainy day, but I'm tempted to seperate the two and grant you the output transformer for a non-excessive fee. The way the transformer is fixed to the loudspeaker in a 938A is different from that in a 834A, so you will have to find a work-around.
Interested?


Regards,

Hans

Plain enough?
If you'd like to contact me direct, click on the tiny envelope next to my name.

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938A, Philips; Eindhoven Radio

door Robert Gribnau, 05.06.2021, 09:40 (1068 dagen geleden) @ gspencer691
Bewerkt door Robert Gribnau, 05.06.2021, 10:33

If for whatever reason you do not aquire the output transformer that Hans offered you, maybe the following is usefull.

On "Vintage Radio Web", the site you got your information/screenshots from, it says that the loudspeaker in the Philips 938A is the 2161.

On "John's Radio Web" it says that the impedance of this loudspeaker is 7.5 Ohm and the impedance of the primary of the outputtransformer is 10000 Ohm (= 10K Ohm).

So since the output power of the Philips 938A is modest, about any outputtransformer with a primary impedance of 10K Ohm and a secondary impedance of 8 Ohm will do.

Greetings,
Robert

Edit: The output transformer has to a "single ended" one, so not a"push-pull" one.

938A, Philips; Eindhoven Radio

door gspencer691 @, 06.06.2021, 20:09 (1067 dagen geleden) @ Robert Gribnau

Can't find the proper words to thank you!

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