OK.? New Discovery.
Dawned on me that the destruction of Q101 (aka Qmumble) might extend to its GATE--and that might explain the unexpected current drain through R6.
Managed to remove Q101 without doing TOO much damage.? ?
Immediate improvement.
No more signs of oscillation on startup even at 12.88 VDC
R6 -- both sides of it are now at supply.? ?Suggests that the 10K on the gate of the MOSFET driven by TX was indeed adequate to keep it from being turned ON by tthe 50K internal pullups of the Raspberry.? ?THAT part of the original design worked.? ??
Output of the 4905 -- now 0 volts.? .? ??
So the ability of the 4905 and the Q101 to be ON simultaneously would always seem to result in the destruction of Q101 and potentially to the problems I experienced with oscillation and loss of components connected to the highpower output terminals....? ?THAT part of the design would appear to need improvement.
Now to see if I can get a MOSFET back in there without destroying it, and with a series resistor.? ? Not sure if I'm game for the RC circuit but thatt appears to be another potential fix.
Gordon KX4Z
