Author Topic: Test mosfets  (Read 2924 times)

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Offline ed1380Topic starter

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Test mosfets
« on: March 18, 2007, 02:10:19 PM »
How do I test one. I only have a multi test and other simple stuff? I think when I was unsoldering them I burned them.
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Offline trigger

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Re: Test mosfets
« Reply #1 on: March 18, 2007, 02:26:07 PM »
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Offline ed1380Topic starter

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Re: Test mosfets
« Reply #2 on: March 18, 2007, 04:22:39 PM »
no diode test range available. will it work with 9 volts?
I bet it's dead since I touched up on them, and unsoldering them with took some time with a 150w gun.
« Last Edit: March 19, 2007, 06:26:08 PM by ed1380 »
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Offline ed1380Topic starter

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Re: Test mosfets
« Reply #3 on: March 19, 2007, 06:26:42 PM »
How do I know if it's a voltage regulator or mosfet. I looked at pics and they look similar.
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Offline trigger

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Re: Test mosfets
« Reply #4 on: March 19, 2007, 07:23:30 PM »
MOSFETs are pretty heat sensitive. If you didn't heat sink it, you might have fried it. 

You should be able to tell it's a mosfet or a voltage regulator by the part number. Just type the part number into digikey and see what comes up.
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Offline ed1380Topic starter

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Re: Test mosfets
« Reply #5 on: March 23, 2007, 07:04:30 PM »
Thanks. that helped. worked for 2 of the 3
I still couldn't find what this was. Heres a pic of whats on it. Looks like 2 diodes to me
« Last Edit: March 23, 2007, 07:05:19 PM by ed1380 »
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Offline trigger

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Re: Test mosfets
« Reply #6 on: March 23, 2007, 07:33:15 PM »
Thanks. that helped. worked for 2 of the 3
I still couldn't find what this was. Heres a pic of whats on it. Looks like 2 diodes to me


Yes, it's probably an NPPN or PNNP transistor (P & N refer to doped regions), which is effectively two diodes stuck together.  So it's got to be a multijunction transistor.  I think it's probably used for transient voltage suppression because I've seen this circuit symbol elsewhere.  Another multijunction transistor, the thyristor for example, is an NPNP (so two diodes stuck together, facing same direction). 

I couldn't find an exact match, but here's an example of a slightly different circuit: 

« Last Edit: March 23, 2007, 07:34:02 PM by trigger »
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