Would anyone have an AUY21K Germanium power transistor .I require it to attempt a repair on an ECU belonging to a 1974 Mercedes.
Regards Jimb.

A few listed on eBay and other overseas sites. Not cheap!

I can see data for this part. NPN, 10A 45 volts but I can't confirm the outline.

If it's a TO3 package then an ordinary 2N3055 should replace it with ratings to spare.

Hello Ian .
Not sure where you got that data from it is a germanium PNP transistor the package is TO3.
Regards Jim

Hello GTC.
Yes I had a look not keen to spend that amount at the moment.
Testing it with an ohm meter it tests ok however I have a Peak component analyser some time it tests ok other times not.
The tester may not like Germaniumm transistors for this reason I am left with some uncertainty .
I would love a circuit diagram of it however Mercedes never released it .
Regards Jim.

I would love a circuit diagram of it however Mercedes never released it

Getting such schematics is often Mission Impossible. Same with Alpine car radios.

MJ2955 Jaycar.
PnP, 100V, 15 Amps. TO3.
JJ

Another comment,
Have repaired several ECU’s but not 3 pointers.
All fixed, ———-dry joints.
JJ

My workshop neighbour has brought a few modern ECUs back to life on a best try but no guarantee basis. Prying them open is half the job and removing the silicone jelly which covers the PCB is another chore. After that he usually finds corroded wires (which are hair like) or bad SMT caps.

I would love a circuit diagram of it however Mercedes never released it

MB is still coy about releasing its service data. I was talking to my mechanic a couple of years ago about how he gets on with servicing German cars and it costs him a lot to get even the basics off German companies. Unlike Japanese and former local companies which by comparison, virtually hand it over on a plate, mechanics pay through the nose, beg and plead for service manuals from the Germans.

By the way, to retract pistons on brake callipers on a Merc, you don't use a $10 G-clamp and a scrap of flat steel like you do on a Commodore, you apparently have to use a laptop and a OEM service manual worth thousands of dollars. It's good owning a Commodore, I have to say, especially if you don't like being torn a new arsehole just when renewing brake pads.

Most car manufacturers nowadays licence the software that allows access to ECUs to 'approved' service people on a per year model basis, and it's not cheap. Guy I know pays a small fortune to GM for the licences he needs to performance-tune GM engines. Given that he does that on a dynamometer, he needs the code to stop the ECU from detecting 'race mode' and putting the engine into crawl home mode.

That's why you have to love the old cars & tractors, there's not a lot of complicated stuff & it stuffs the young ones as there's no plug for the computer. You actually have to know how it works. The genuine Zephyr radio & early Holden ones had there respective radio circuits in their genuine factory manual.

Yes I was expecting it to be a PNP transistor like an AU103 but the data says otherwise.

However when I look again, the datasheet is confusing in that it also covers its complement.

Testing it, just look for valid diodes using an ohm-meter

Thank you all for your input.
Ian my normal testing method is the ohm meter and in this case it was also. However I also have a Peak component analyser there are two of these transistors it initially tested one OK the other it ignored the base connection. I have since tested the good transistor several times at occasionally it gave the same inconsistent result. So yes I believe the multimeter is correct and they are OK. Fortunately the ECU on my Mercedes is OK this one belongs to a friends Mercedes. My car was used as a test bed. I have proceeded with extreme caution it it was mine and I had no alternative I would get stuck in. The rear heat sink has some components with 6 legs with high temperature leads hanging out of them which would require some serious effort to remove so I can identify them. I have very bad shakes which makes me very cautious I do not want to go where Angel's fear to tread. His best bet will be to source another from a wrecker then I will have another go. I was an electronic tech by trade Broadcast TV Industrial and commercial electronics however those days are no longer with me and radio repairs are now difficult due to the dry paste joints I am guilty of from my hands oscillating.
Kind Regards Jimbr

Jimb.

I have a good ASZ18, which is listed a replacement for the AUY21. It has a higher voltage rating, and a lower base current to make it turn on.

I could not find any reference to the letter K at the end of the designation. My feeling is that it a grading as to gain, probably requested by the purchaser.

Yours if you need it.

You have my details.

Regards

Wayne.