Looking for Transistor AD155 or substitute

Thread Starter

Mahifa Rahid

Joined Apr 1, 2018
G'day folks,

I migrated to Australia from Germany in 1974. I used to own a Schaub Lorenz T60 Transistor Radio in the 60s. For nostalgic reasons I purchased the same radio on German eBay. Quite expensive because of the shipping. It was advertised as fully functional. But it is not. All I get is very weak and distorted volume. I traced it down to the two AD155 final stage Amp transistors. Short between emitter and collector, measured desoldered. I'm actually a retired carpenter tinkering in old analog gear - especially organs. I know a "little" about electronics. I suspect that unsuitable or defective gear was connected to the audio out. There are a few expensive AD 155 transistors on eBay, but there are also some cheaper Russian substitutes offered (GT403E or 1T403E). There is also the issue of matched pairs! I think the Germans call it "Gegentakt Endstufe". But I'm only guessing here. Please enlighten me.

Thank You


Joined Nov 22, 2017
Thank you all. I don't know where I've got the idea from that the radio has a "Gegentakt Endstufe" - requiring a matched pair. I am thinking of ordering a pair of these: https://www.ebay.com.au/itm/ADP670-...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
Would they be suitable?
Transistors of your transformer amplifier really need to be matched for current gain and leakage current.
In your link transistors looks like not matched.
For example: https://www.kevinchant.com/germanium-output-transistors.html
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