I haven’t, I haven’t carefully validated your measurements yet. ?
I did change the coupling capacitor from 47 pF to 330 pf— thinking the DC supply isn’t getting enough supply
We are definitely onto something. I’m not sure this “doubler” is doubling
I got my scope to tell me the peak voltage
-Peak AC voltage of RF at the moment is running 25 volts give or take
-peak back bias voltage going to the inductors in the other stages is on the order of 23 to 24.2.?
Obviously, this is not enough backbias!!!!!!!!
Something is bad wrong with the little DC supply in this radio. ?
Gotta go again, but I’ll get back to Gus. I think we are onto something ?thing important ??
Perhaps a diode is backwards or blown up?
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On Nov 10, 2023, at 11:19, Evan Hand <elhandjr@...> wrote:
?Hi Gordon,
I agree that your harmonics measurement eliminates the wire as an issue.
The voltage for a 15-watt output should be higher than 40 volts, closer to 70 volts.? The 10x scope (10M Ohms) probe should not load down the doubler.? I think you may have found the issue.? I suggest pulling the diodes to verify that they are OK.? With the diodes removed, you can verify that there are no shorts on the HV line.
If you have a greater than 40-volt bench supply, you could connect it to the HV line to test.? The current requirement would be much less than 1 ma.? If your highest bench supply is 30 volts, reduce the power to less than 8 watts and use it.
By my back-of-the-envelope calculation, the doubler should produce around 52 volts with 15 watts.? You need at least 39 volts (the peak voltage of the transmission plus a diode drop).? I used 40 volts as a buffer and 8 watts for the 30 volts supply.
Check my calculations, and please let me know if I am in error.
73
Evan
AC9TU
