"Arfa Daily" wrote in message
...


"Phil Allison" wrote in message
...

"Arfa Daily has No Idea how STUPID he is,. "


A new pair of matched transistors had the offset down to a few mV, and
the protect circuit was happy with that. But it got me to wondering what
could be the failure mechanism that resulted in a transistor still being
a recognisable transistor in that the tester still saw it as one, and it
still basically worked in the amp, but had a very low gain ?


** Obviously some kind of manufacturing defect in the particular
transistor - thousands of possibilities.


Don't know why, but see it fairly often. Seems like a preamp pair can
function with mismatched hFe up top a point but when the gain difference is
too great, DC offsets, sometimes intermittent, occur.

Just the other day had two relay drive transistors in a Marantz 2270 with an
hFe of 2. Don't know for sure how or why they failed, but I did notice black
tarnish on the leads. Perhaps migrated into the semi material?

Mark Z.