[amb]

I posted the info here and at headwize in the past, but it gets buried in threads and hard to search for, so I wrote a new one with more details and illustrations, and made it a sticky topic at my forum. I hope this is helpful info for any of you troubleshooting a circuit with discrete BJTs:

AMB Laboratories DIY Audio - View topic - HOWTO: BJT sanity check tutorial

 

[regal]

Quote:

Originally Posted by amb /img/forum/go_quote.gif I posted the info here and at headwize in the past, but it gets buried in threads and hard to search for, so I wrote a new one with more details and illustrations, and made it a sticky topic at my forum. I hope this is helpful info for any of you troubleshooting a circuit with discrete BJTs: AMB Laboratories DIY Audio - View topic - HOWTO: BJT sanity check tutorial

Thankyou but I always used my component tester to check HFE, is it possible to have a bad BJT that would pass the HFE test?

 

[amb]

Quote:

Originally Posted by regal /img/forum/go_quote.gif Thankyou but I always used my component tester to check HFE, is it possible to have a bad BJT that would pass the HFE test?

If the transistor is bad, then the Hfe test should yield bad result too. However you must remove the transistor from the circuit to check its Hfe, whereas the method I outlined could be used in-circuit with some caveats.

Note that neither of these methods would identify a noisy transistor, or some other aspect that might make it not meet specifications.

 

[regal]

Quote:

Originally Posted by amb /img/forum/go_quote.gif If the transistor is bad, then the Hfe test should yield bad result too. However you must remove the transistor from the circuit to check its Hfe, whereas the method I outlined could be used in-circuit with some caveats. Note that neither of these methods would identify a noisy transistor, or some other aspect that might make it not meet specifications.

Ok, I learned a long time ago to use sip sockets with BJT's, so pulling and replacing them is easy.