Well, that's good news. Now: how about my Crane transistorized ignition
trigger? Damaged?
On 8/28/07, Alex <alexmm@roadrunner.com> wrote:
>
> John, it's possible that when your friend upgraded your fuel pump he may
> have installed a series diode in the 12-V line. The diode will only
> conduct
> in the forward-biased direction. If polarity is reversed, the diode would
> be
> reverse-biased, protecting the downstream circuitry within the pump,
> namely
> the transistor. That's one possibility.
>
> The other is that the transistor simply was robust enough to withstand the
> reverse polarity. With reversed polarity on the base of the transistor it
> will not conduct, thereby protecting itself. A transistor's
> base-to-emitter
> junction must be forward-biased for the device to conduct (act as a
> switch).
> It conducts from emitter-to-collector.
>
> == Alex in Maine
> "The Blue Mainie," 1960 Austin Healey 3000 BT7
> "Conkling," 1946 MG TC #1321
> Former owner 1957 A-H 100-6, 1967 A-H BJ8,
> 1965 MG Midget
> http://users.adelphia.net/~alexmm/ai2q.htm
>
>
> ----- Original Message -----
> From: "JohnD" <johnsfolly@gmail.com>
> To: "MG" <mg-t@autox.team.net>; "Rick Fisk" <refisk@chartermi.net>
> Sent: Tuesday, August 28, 2007 9:45 AM
> Subject: Transistors, diodes and fuel pumps
>
>
> >A question for you electronic types: About 20 years ago, while siting at
> a
> > bar in North Wildwood, NJ, a friend of mine did the transistor upgrade
> to
> > the low pressure SU fuel pump from my TD. It has worked flawlessly and
> > burned points have been a thing of the past. However, last weekend, I
> > dropped in an Optima battery a friend had given me, and like a dummy, I
> > connected it with a negative ground instead of the appropriate positive
> > ground. Course, when I turned on the key, the fuel pump remained
> silent.
> > I
> > banged on it, and did the usual stuff-- but the power was reversed
> through
> > it for quite awhile before I came to my senses.
> >
> > Last night, I noticed my stupidity, turned the battery around, and the
> > fuel
> > pump started right up!
> >
> > Why did the polarity-sensitive electronics not "fry" when the
> got juice
> > in
> > the "wrong" direction? Should I assume pump failure is near in my
> future
> > and swap pumps now?
> >
> > Many thanks for the education.
> >
> > JohnD
> > --
> > Racing in the Past Lane!
>
>
--
Racing in the Past Lane!
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