I guess this is what seperates the $30/hour teks from the $15/hour
techs. You need to look at the application.
If an N channel you need to figure out if they are giving it negative
or positive drive. That tells you if it's enhancement or depletion. If
it's a power FET it is most likely enhancement, the reason for which is
beyond the scope of this text.
Just WHERE is this FET ? At the input side of an audio amp, in a
switchmode PS ? the application matters the most. If it's a chopper for
SMPS and the line voltage is 110 you need about a 400V unit, if 220 you
need about a 900V unit. Current is the next concern, just what does the
thing run ? A wattage rating on the back panel might shed some light on
this.
Or is it in an RF application ? If so these are the hardest for which
to figure out a replacement.
I know it's not easy for everybody, but if you could draw just a
partial schematic of the circuit it's in it would be "worth a thousand
words". If you HAVE a schematic all you need to do is scan a part of it
and we'll know what is needed.
If you do draw and/or scan DO NOT post it to the NG as a binary,
everybody gets pissed off about that. Almost every ISP gives you some
FTP space, upload it and throw a link in here.
JURB
