Silicon transistor failure

[agardiner]

Hi Terry,

So I cannot comment on breakdown voltage as I haven't run any tests. At this stage though, I would not have thought that there is a high risk of complete breakdown in AF stages; yet.

The problem I am regularly coming across, is transistors that have gone low gain, or in some cases, noisy. Low gain transistors cause issues such as RF oscillators to fail, and I have also found AF low gain transistors in audio amps, causing channel mis-match. Checking with a multimeter doesn't show any issue, as the junctions still test just fine. You either need an in circuit test with say a scope, or test the transistor with a transistor tester.

Certainly in the case of radio where the oscillator is not running, my first call now is to replace the transistor and see if it solves the problem.

Regards,

[kalee20]

Just thinking... if epoxy degradation is affecting transistors in TO92, how much more will op-amps in plastic packages be affected where there's considerable gain after the first stage?

[Trevor]

Oh no I have thousands of old transistors I thought they would last for ever !