Thanks to the group for the help on my 38S debagle. Here's what happened
and the resolution to this point:
First: The working 38S w/ 5watt mod/TICK mod went into a case. The routing
of the power leads passed next to the hot Q2 case and the cheap insulation
melted shorting the final to ground. The coil L101 literally burned up. I
replaced to coil and final. No other components appeared damaged, however
when I applied power in recieve Q2(final) temperature ran away. A bias
voltage problem? but from where?
Ori AC6AN sent me a great doc on troubleshooting the S38, but voltages were
hard to test with the final in place, so I applied power for very short
bursts to take voltage readings. U4 pin 20 was down to 2 volts. I pulled
VR1 and found the voltage output at 6.8 volts. In checking the circuit I
thought maybe this was a nominal reading but when I replaced VR1, a solid
8V came back, and a cool final as well.
I guess voltage regulators can partially fail or change value under this
kind of stress. I assumed, incorrectly, that the device would either work
or fail.
It could have been worse,it could have been U4 which is soldered in.
Now..... What frequency is it on is the question?.... that's next.
Barry
K6ZA
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