It seems that just blindly replacing blown IRF510 devices with more IRF510's
is an exercise in treating the symptom instead of fixing the problem.? There
are many ideas and myths about why the IRF510 devices sometimes fail but only limited definitive information on what actually causes these failures.? We have empirical information indicating that if the SWR is high they will fail, but limited information on exactly why that is the case and what the mechanism
On Thu, Mar 15, 2018 at 10:59 PM, John Backo <jabac@...> wrote:
These HEXFETS are rated for 200V and 50A. They will (sorta) work as you have shown.
But the gate input capacitance is 4000+ pF. That increases your standing wave in
the drive circuit and lowers your output considerably. You have 2 choices:
Either replace the finals with IRF510s (after you have figured out what blew them up),
or figure out how to lower the input capacitance to 180 pF. or so. You can also probably
safely use a drain voltage of 48v or so, but there would probably be oscillation which would
have to be accounted for. Incidentally, how do you know they are not oscillating now?
Since the potential drain amperage is so high, it is probably wise to provide a current limiter
if you have not already done so, especially using wspr or another more or less continuous
wave function.
