Hi Barry,
Good news. We did try shorting C-E of Q8051 and it didn't change the output, it should have eliminated any effect of Q8051 as the only root cause, i.e. there must have been something in addition to possibly bad Q8051. Perhaps the test was done before you fixed the broken traces and/or swapping 2N2219A. Congratulations for the repair, it was an interesting puzzle.
Ozan
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On Sat, Dec 28, 2024 at 07:25 AM, Barry Breaux wrote:
I finally got to the bottom of this! A great learning for me. The bottom line
is that the Q8051 transistor needs a lot of gain to drive 2n2219A. The
original transistor was a PN3565, 151-0341. The original was bad so I couldn't
measure it. I had only 2 of those on hand and the one with a gain of 465
worked.
Onan, Thanks for all the help you provided me. I am sorry if some of the
information I provided was a bit unclear. In the end I learned a lot. Many
thanks!
Barry
