Hello N1BUG, I don't change any that remain functional and haven't had
an issue. I do use a very cheap Ebay IR temp gun to check all run
similar temperatures and find that a good way to see if one is working
overly hard. I just checked, it's the 32N20 that I have always used. I
think it's the voltage rating rather than current that's a bit
marginal. and there are probably much better FET's with lower gate
capacitance around nowadays for similar cost, but I am loathe to
fiddle until it becomes necessary :) I was talked into buying a used
Metcal RF soldering station at a rally some years back. Best thing I
have ever bought electronics wise. With a high temp tip it will
de-solder and re-solder the drain wire from the copper strip so fast
everything else does not melt. Until you try one it sounds too good to
be true, but I am now 100% converted. With a small tip it is great for
surface mount tiny stuff, too.


Tuesday, November 20, 2018, 3:32:50 PM, you wrote:

> Hello Chris,

> I would be interested in the collective wisdom of the wise ones in
> this group regarding replacement of FETs. Given they've all surely
> had a strain when one or more blew, is it really wise to just
> replace the ones that check bad? I'm leaning toward replacing all
> four whenever one or more is dead. Am I being too paranoid?

> I really wish we could socket the FETs.  When I am in there this
> time I may see if I can find a not too messy / not too destructive
> way to mount those copper strips the FET drain leads solder to so
> they can't move around. When replacing FETs I find it oddly
> aggravating holding that metal strip in place. Invariably the heavy
> lead from the transformer then comes unsoldered from it and I have
> to try to put that back without any drain leads or the snubber cap
> coming unsoldered. It'd be nice if that copper strip were solidly
> mounted and the transformer lead bolted to it (I think)...

> I can still get FETs in the big package if I go 32N20 instead of 34N20.

> 73,
> Paul





-- 
Best regards,
 Chris                            mailto:[email protected]