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Question for the Electronic gurus

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I have been working on finishing an old project which uses the ms20 pir. I have it working with a w50 cam.

To make a long story short, I was fitting things today and decided to do another test after adding another regulator to my controller. I grabbed a 12v battery pack and flipped the switch on and nothing. I realized I screwed up putting 12v to it instead of my 9v.

Well I had to do some cutting to get the sensor board out to see what happened. I tested a few points comparing to another one and it looks like I fried Q1.

Anyone know what a ST25A - 733p is?  ...  I've searched high and low and am unable to find what it is.

I assume it's some sort of transistor, 25 amp and would think it should be high voltage as well..I

I'll post a pic in a minute..

ms20 repair.jpg

Edited by bulltalk.65

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2 hours ago, ko4nrbs said:

Looks like it is a transistor.




Hi Bill,

That's what I assumed. I sure would think it could handle 12v though since it was on the sensor, although with all the removed parts it might not.

I'll probe around it some more and see if it's something else.

With a battery connected I should see the nominal voltage on it but I'm only getting 1.7v across it so something is awry somewhere...lol

I ended up just grabbing another one out of my box and hacking it and installing it and will mess with this one later to see if I can get her Workin again.

Edited by bulltalk.65

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