[86coupe]

Hello,
I am currently finishing up changing my car from SD to mass air, I have a C3W1 computer I am using and the number 2 injector transistor is toast, unfortunately I am unable to locate a replacement one, are these obsolete, I can't seem to find any cross reference info on it either. The part number on it reads (04S74 041)
Any help would be greatly appreciated
Thanks

Transistor.jpg

[tensecrab]

Yes, the 04S74 041 injector driver used in the C3W1 ECU is obsolete. You won’t find it under that marking, but it’s essentially an ON Semiconductor Darlington power transistor. You can replace it with an equivalent like TIP120, TIP122, or MJ10012 after matching the specs, or salvage from another C3W1 ECU.

[86coupe]

Yes, the 04S74 041 injector driver used in the C3W1 ECU is obsolete. You won’t find it under that marking, but it’s essentially an ON Semiconductor Darlington power transistor. You can replace it with an equivalent like TIP120, TIP122, or MJ10012 after matching the specs, or salvage from another C3W1 ECU.

Thank you so much for your response, this may be a dumb question but how would I go about matching the specs?

[Jman]

I don't think you will be able to know for sure you have matched the specs because a datasheet for the 04S74 doesn't seems to exist. I found a couple 04S74's in some old EECs I have laying around and put them into my cheapy transistor tester, and the 04S74 is a NPN Darlington transistor. I would recommend using a TIP102. I have not tried this but think it's a suitable replacement and it's stronger than the TIP122 by a few AMPs. Below are the pictures of the GE/RCA 04S74, and a Motorola 04S74, and TIP102. The Gain or Beta (B on my tester) varies even between the two 04S74's but I wouldn't be too concerned by that because as far as I know these are being used as switches and the gain is more important if a transistor is being used as an amplifier. In a switching circuit the base of the transistor is driven harder so the transistor fully saturates meaning fully ON.

It would be great if someone with a better understanding could look at the pictures and chime in. It would be cool to change one injector transistor on an A9L (sequential injection), to a TIP102, and use a scope on a running mustang to look at and compare the waveforms between the two different transistor outputs right at the injectors. Unfortunately, that's a bit of a task to do for curiosity's sake.

If it were me, I would try to change the transistor to a TIP102 but if it's a bank fired setup, I think I'd change both injector drivers, so they matched.

Has anybody out there ever swapped out an injector driver to transistor that's newer and actually available? If so, what part did you use?

Thank you
J.W.S.