JFET Heating Up in Testing

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Lostininverness
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JFET Heating Up in Testing

Post by Lostininverness »

I have put together a JFET matcher (used the pcb etch from Jacob Kokrua of JMK Pedals) and stuck in a 2N5952 to see if its working (guess what I'm building - yep, phasey goodness ahead I hope).

So the DMM gives the value for the Vgs in the right ball park, but the transistor gets quite hot to touch while awiting for the reading to settle. Do any of you know whether this is "normal" for transistor in a tester, and if it might damage the transistor?

Thanks for your help.

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Re: JFET Heating Up in Testing

Post by alanp »

Shouldn't heat up. Pin-out correct?
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Lostininverness
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Re: JFET Heating Up in Testing

Post by Lostininverness »

Hi Alan, hoped you'd reply - I was looking for info on the madbean forum when I saw some of your older posts.

It may not have been, although I thought I did try it the correct way and wasn't getting a reading...

Do transistors only heat up when installed incorrectly? Something to do with not able to dissipate the voltage?

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Re: JFET Heating Up in Testing

Post by alanp »

My FET tester is the one from rullywow, used it to test 30 2n5457 fets for the PS-1A build. They didn't get hot.

Get the datasheet for the 2n5952, and check your pinout relative to the PCB pinout.
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Re: JFET Heating Up in Testing

Post by Lostininverness »

yep, spot on, think I was installing them in wrong way around - what a fool.

But on the plus after a bit of time, have managed to sort 50 fets into one quad set, 15 pairs and a pile of "outliers". Now can build a P90!

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