Date: Mon, 18 Dec 2000 02:27:02 -0500
From: "Holger 'Geri' Kinzel, DK8KW" <DK8KW@compuserve.com>
Subject: LF: OM2TW
To: rsgb_lf_group@blacksheep.org
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Rich, OM2TW wrote:

>I was on my LF site during this saturday, but I burn all my mosfets.
>Something is wrong with my power amplifier. After a few weeks of
problemless
>operation, one mosfet has been broken.<

... do those FETs come with a build-in expiry date? I, too, have broken a
couple of them during the weekend (well, I must admit, I tried to run the
G0MRF PA on a 56 Volt rail instead of the usual 28 Volt I normally use ...
what I found out is that the length of sparks that are crerated when the
FETs explode is directly proportional to the voltage ... *very*
impressive!). When I changed back to 28 Volt (partly with new FETs) and
tried to re-adjust the bias, another one burned (... yes, with a smaller
spark, as expected). Maybe this is due to mixing IRFP450 with the "new"
type IRFP450A (but the data sheets I retrieved from the Internet show
absolutely no difference in the performance data ... or did I miss
something?).

Question: Anyone tried to replace the IRFP450 with the IRFP460? Seems to
have only half the RD-on, all other data look quite the same. I found a
source where they cost 6.10 DM and I would like to give them a try.

Best 73

Geri, DK8KW (W1KW)