Re: MAC11b ECU Trials & Tribulations

[Orin Eman <orin@WOLFENET.com>]

>     I've also looked into the 'swap senario' and found that the NEC part
> (2SC 2334) has the following specs:
> NPN silicon, TO-220 (case style),
>     (1) 150V Collector-Base,
>     (2) 100V Collector-Emitter,
>     (3) 7V Emitter-Base,
>     (4) 7A Collector Current,
>     (5) 40W Max Power Dissipation,
>     (6) 5MHz Max Frequency,
>     (7) 40(min)/200(typical) Current Gain,
>     (8) 3A Bias Current for gain.

7A collector current/40 min gain requires .18A base current.
It's driven by a D789 with a mondo 68 ohm resistor collector to 12V,
which actually gives .18A (12/68) base current.

> The TIP41C (Philips/various) has the following specs:-
> NPN silicon, TO-220 (case style),
>     (1) 100V Collector-Base,
>     (2) 100V Collector-Emitter,
>     (3) 5V Emitter-Base,
>     (4) 6A Collector Current,
>     (5) 80W Max Power Dissipation,
>     (6) 3MHz Max Frequency,
>     (7) 15(min)/75(typical) Current Gain,
>     (8) 3A Bias Current for gain.

.18 * 15 = 2.6A.  May not be enough to open the injector.
If they had 100% margin on the base current above, that would imply
3.5A is required to open the injector which sounds about right.

> Igor's 2SD866B (Matsushita/Panasonic):-
> NPN silicon, TO-220 (case style),
>     (1) 130V Collector-Base,
>     (2) 80V Collector-Emitter,
>     (3) 7V Emitter-Base,
>     (4) 7A Collector Current,
>     (5) 40W Max Power Dissipation,
>     (6) 15MHz Max Frequency,
>     (7) 60(min)/260(typical) Current Gain,
>     (8) 3A Bias Current for gain.

> My .02c worth - go with Igor's Part! this particular transistor (2SC2334)
> has quite a high current gain for a power device, using a TIP41 could let
> you down in a big way.

Given this choice, I would too.  (Though I have a feeling a Rat-Shack
TIP120 would work.  Plenty of gain and the darlington config would
work in the circuit.  Vcxx voltages are lower, but the circuit
protects the transistor with a zener from B to C and diode
from E to C.)

Orin.