[Diy_efi] Driving injector: forward biased diode between B and

[Stephen Webb]

> If it's pretty old vintage (and something tells me k-jetronic is) you're

This flavor of K-Jet was born in the early '80s, if not late '70s.  This
particular unit is from an '89, but is the same part number as
applications going back to the early '80s.  I'm not sure if "early
'80s" qualifies as vintage or not.  

> probably correct that it's bipolar.  What kind of package?  to-220? 
> Does it have a heat sink?  You should really desoldier it and then use

TO-220 w/ large-and-in-charge heat sink.  I didn't really want to desolder
it, but may do so.

> configuration.  Usually, the legs are EBC or CBE from left to right,
> when looking at the front of the package.

"Front" meaning heatsink away from me, pins pointing down?

I say it's BCE, but what do I know?

Leftmost pin is connected to the IC that controls it, which would make it
the Base, I think.  Second pin is connected to the load (a 10 Ohm, 10 watt
resistor in series with an "injector".)  The other end of the injector
gets +12V.  The third pin goes to ground.

Smells an awful lot like BCE NPN to me, but that's not a hard conclusion
when all I know about are NPN transistors anyway.  :)



> If it's really a collector-base diode, it's probably just for protection
> of the CB junction (iirc, that can be sensitive to reverse-bias

Another member of the list sent me schematics to some EFI circuit, and
it sure appeared to use an NPN with a diode in the same way (that is, If I
can read schematics correctly)

I think I am convinced that it's NPN, and the diode is like I have
described.  I was hesitant to copy the circuit since I didn't understand
it, and I feared the "NPN transistor" would turn out to be something else
(which needs a diode, and my NPN circuit woudln't) etc, etc.

Thanks for the help

-Steve



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