On 11/1/2019 1:30 PM, nm0s_qrp via Groups.Io wrote:
voltages measured for Q3 and Q11 swappedAh, no, but I read "IRF-510" and forgot there were two of them, and I was measuring Q1 instead of Q12. Thus my argument about 0 volts on the drain and resting carrier, etc.
Let me try again with new measured values:
G D S
Q3 9 10.3 12.6 FQP7P06
Q11 7.5 3.5* 12.4 FQP7P06
Q12 5.6 3.5* 2.4 IRF510 (NOT the PA one!)
* the voltage at the drains of Q11 and Q12 measures 3.5V right after the PTT is keyed, but start to rise rapidly, which creates the thermal runaway problem. The voltage is > 8 volts within 15 seconds or so and when I measured the temp of the Q11 heatsink it quickly rose to > 50 deg.
As with the values your provided, all the above are with PTT keyed but no modulation.
Sorry for the mixup on Q numbers. Does this suggest anything new?
73, Bob W9RAN