Rm italy klv250, help!

[boog351]

I've been asked to look at this thing, looks like an old k1313.
Klv250, rm italy mosfet amp.
I'm a glorified tinkerer, tinkerist? I can solder and have some old test equipment, and some knowledge, but far from an expert, and not and amp guy, so please forgive any ignorance.
I don't have much experience with mosfets, I've been away from the hobby for a while.
The amp...
It has been blown up a few times.
The 4 factory rm3s? had been replaced with irf520s which were blown, then replaced with new rm3s and blown up again in a day or so.
My questions are, would anything have been changed to make the 520s work, or are they somewhat drop in?
From what research I did the rm mosfet info is top secret.
The amp currently has the mosfets taken out, what should I look for as far as voltages etc? On high vs low, Or any other ideas of possible problems to look for.
I don't want to just throw another set of mosfets in just to have it pop again.
If I can go by 520 specs to look at voltages then I can figure that part out.
Should I be using a vtvm or would a dvm be fine?
I thought I'd ask here to hopefully save some time when I get it back on the bench.

 

[9C1Driver]

That klv250 is very much a low low drive amp, that's probably why it keeps getting smoked. I'd put the RM3's back in and then have the owner run it with a 1.5 watt dead key and 10-12 peak. On SSB run 10-12 PEP. I would also put a fan on it and it should last a long time that way.

 

[nomadradio]

Don't tell me, let me guess. The owner drove it with a General Lee.

There are three 1N4148 diodes and a couple of zener diodes that control the gate voltage on the MOSFETs. They can become collateral damage when MOSFETs fail. If they are damaged and the gate voltage is too high, you'll poof new MOSFETs at a pretty rapid rate.

73