grundig: Faulty Germanium transistor on City-Boy
? grundig: Faulty Germanium transistor on City-Boy
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My City-Boy had constant hissing sound which was traced to a faulty TF65 (AC125) transistor on the amplifier section. I temporarily replaced it with a bulky TF78 and it seems ok, but are there any online shops selling old transistors? I would be glad to know your ideas and suggestions. Thank you very much!
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Germanium Transistors
Many Eastern European sellers on eBay have both domestic and military "NOS" Germanium transistors of Russain or USSR origin. Just select parts with suitable voltage, power and frequency rating for the application, rather than equvalent or better spec.
I've used a 60MHz part to replace the usually faulty AF117. Audio parts other than higher power audio (such as AD161 AD162) are easier to replace than RF parts.
Western European parts are also available, but can be extremely expensive. AC125 should be no problem. Parts like AF117 are usually better replaced with AF127 etc due to tin whiskers inside the can. Littlediode is I think one western source specialising in obsolete parts. They sell on their own site and ebay.
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grundig: Faulty Germanium transistor on City-Boy

TF65 are for sale on eBay quite cheaply.
Andrew
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grundig: Faulty Germanium transistor on City-Boy

Pls send email with address. I can send you two pieces. If you have a SI pnp transistor you can adapt R55 to e.g.18k for equal emitter current of the LF-driver stage.
Rudi
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