tranisitor help

Aug 21, 2006 2 Replies
I

Hello,



I have a home irrigation controller hat has gone faulty on one of the zones, I have opened it up and have found one of the transistors to be faulty there is a number on the transistor but it looks like its a part number from the manufacturer of the irrigation unit rather then the actual part number of the transistor.



The number written on it is 1401ES or 1401E5 cant make out if its a 5 or an S but looks like an S to me and sound like it might be an NPN transistor.



The purpose of this transiston from what I can tell from the board is to turn a solenoid on and off.



The Irrigation unit is made by Holman Distributors.



Any help you can provide would be greatly appreciated.



Thanks Imran Khan


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R

Simple. Measure the voltage between the collector and the emitter to determine NPN or PNP; even if it is "shorted" usually the resistance is high enough to read at least 50mV and thus get polarity. Then replace with any transistor of same "sex" and similar power rating; if original has a heatsink or is on a heatsink, then same case.

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W

If only one of the zones is bad, you might be able to measure the corresponding transistor from one of the good zones, to figure out whether it is indeed an NPN transistor (as opposed to, say, a MOSFET). That will also tell you whether it's a Darlington or normal transistor; normal transistor Vbe is around 0.6 to 0.7v, where a Darlington would be twice that.

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