In going through NA5Y's QRP-Labs 50 watt amplifier trouble shouting guide and doing all the voltage measurements both on receive and transmit
I found a discrepancy at the very last test point on the video.??At the test point located at the intersection of R8, L5, and the two 1N4007? diodes the voltage is supposed to be about .07 V on receive and about 70 volt on transmit.? But at that point on mine it is .1 V on receive and only 36 volt on transmit.
In other words it is almost exactly half what it should be on transmit.? This test point is right after the voltage doubler portion of the circuit which suggests that for some reason the voltage isn't being doubled.? That suggests to me the remaining trouble may be among the components that make up the voltage doubler?
(the four 1N4148 diodes and two 47uF capacitors). Alternatively I suppose the voltage doubler could be working but the signal presented upstream was half what it should be before passing to the voltage doubler. (I don't have an oscilloscope to check the RF input to that location.)
Prior to doing these tests I had replaced the two IRF510 final MOSFETs Q1 and Q2 as well as the two BS170 transistors .
With 13.4 Volt supply voltage and the R5 variable resistor set fully counter clockwise watt meter shows 8 watts of output power.
And still have the strange behaviour THE RED TRANSMIT LIGHTS STAYS ILLUMINATED FOR ABOUT A FULL SECOND AFTER A KEY PRESS and release.
This red LED dims slowly after key press release instead of being nearly instant off.? Help me understand this? Where is the power coming from to allow this slow LED extinguishment?? ?And which component to replace next? Thanks again in advance for any advice.
