Oops, the link to the ARRL note was truncated, here it is again:

http://www.arrl.org/files/file/Technology/HandsOnRadio/Thoughts%20on%20Reverse%20Power%20Protection%20using%20Power%20MOSFETs%20-%20Wheeler%20N0GSG.pdf

Bob NW8L

---In 4sqrp@..., wrote :

Yes, I ran into the same problem, Q6 failed and was running extremely hot etc. not long after I built the kit.

At first I removed it and completed the (-) path with a piece of wire, later I replaced it to restore the polarity protection it offers.

The gate of Q6 (a MOSFET) is directly connected to the (+) input power pin. I suspect that it was damaged by static discharge, so now I'm very careful when connecting the power to the radio.

Eventually I'll lift the gate lead of Q6 and kludge in an RC ESD protection network like that seen in figure 2 of this ARRL note:

http://www.arrl.org/files/file/Technology/HandsOnRadio/Thoughts%20on%20Reverse%20Power%20Protection%20using%20Power%20MOSFETs%20-%20Wheeler%20N0GSG

If that works out I'll have additional peace of mind, it's very dry here in NM and electrostatic discharge can be a problem.

Bob NW8L

---In 4sqrp@..., wrote :

I am finding that my reverse voltage IRF510 is running hot enough to burn my fingers, even when the BJ is switched off. I was questioning why my Jet Ski battery was running down after a few days of "just sitting on the bench" while connected to the turned off BJ.

Any suggestions?

Also the receiver oscillator transistor seems to be the temp sensitive wandering part. I sprayed lightly each part with coolant air and that part seems to move frequency the fastest and the farthest. The toroid is also temperature sensitive but less so.

Dave K8WPE

Dave K8WPE