Transistor info needed on Motronic ECU

Gary Waggoner

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I need transistor T221 on a Motronic 1.3. I cannot get info on which type it is......Don? It is up against a relay on the board so even if you have an ECU, you would be hard pressed on seeing the part no.
 

sfdon

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Bosch is world famous for not sharing their tech info.
Nobody allowed in their vault building.

Just buy the one in LA for 30 bucks.

PM to you with info.....
 

Arde

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Not sure if T221 is the High Voltage Ignition Coil Driver, in that case I read it can be a SGS/Thompson BU931P NPN Power Darlington.
 

Mike Goble

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Not sure if T221 is the High Voltage Ignition Coil Driver, in that case I read it can be a SGS/Thompson BU931P NPN Power Darlington.
Who could forget Sidney Darlington...
Always a tinkerer, Darlington in the 1950s spent a weekend at home playing with a new gadget, the transistor. Trying to get more gain from an amplifier the size of a kernel of corn, he found a way to combine two or more transistors in one chip, an idea that became the Darlington type of Compound Chip and pointed the way toward integrated circuits. He patented the idea and lived to see the Darlington chip become required study for electrical engineering students everywhere. Darlington also made advances in radar, inventing the pulse compression ("chirp") radar in 1947. This approach, using several frequencies to lower the demands for high peak power, made possible the antiballistic missile defense system.
https://ethw.org/Sidney_Darlington
 

Gary Waggoner

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Problem is that I know the location of the transistor(t221) but not sure which type it is. Bosch is no help and neither are the ECU rebuilders out there. It appears the easiest way is to buy a used similar ECU and rob parts.
 

Ohmess

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Gary -- can you provide the information you have on this transistor. Pictures would be helpful. I had some analog video equipment I messed around with a few years ago and part of the process was troubleshooting the various control boards, including the identification, sourcing and replacing capacitors, resistors and transistors.

If the transistor is a SGS/Thompson BU931P NPN Power Darlington, Mouser sells these for $3.19 and has 151 in stock:

 

Gary Waggoner

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I purchased the ecu on ebay, but it is completely different than the s38 one I have. I was hoping for the main realy circuit to be the same so I can identify the Trans that I need. Unfortunately the one in question is unreadable and although it is a t0-92 design, I do not know which one of the 4 or 5 that BMW seems to use in the ECU. It is possibly a 548C or 558B. Both are cheap and easy to get, but not sure which one. I do know that it is in the main relay section of the board, but thats it.
 

sfdon

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I purchased the ecu on ebay, but it is completely different than the s38 one I have. I was hoping for the main realy circuit to be the same so I can identify the Trans that I need. Unfortunately the one in question is unreadable and although it is a t0-92 design, I do not know which one of the 4 or 5 that BMW seems to use in the ECU. It is possibly a 548C or 558B. Both are cheap and easy to get, but not sure which one. I do know that it is in the main relay section of the board, but thats it.

Maybe time to contact Programa?
 

Gary Waggoner

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Update...found a small chip of plastic on the shop floor and it was the piece that had the first 2 digits that were needed to figure out exactly which trans was needed. Thanks for the help with this all.
 

Arde

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That is why I never vaccum clean my living room...

Update...found a small chip of plastic on the shop floor and it was the piece that had the first 2 digits that were needed to figure out exactly which trans was needed. Thanks for the help with this all.
 

Ohmess

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Nice. Sounds like you are heading toward a happy ending.

If you have time, it might be nice to post the result of your efforts here in case someone else has this same problem.
 

Gary Waggoner

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I would have been at the mercy of sending the ECU off for repair at a very high cost if I had not found a small piece of the transistor that must have fallen out of the case when I opened it. I found a seller for the replacement part and am soldering it in now. I do have a rather large assortment of transistors now though. If anyone needs any of this style transistor I have many different models and variances
 

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