[Lowfer] FET change, hmmm

[DAVE PICK]

Paul

Try the Infineon IRFP260MPBF they are fast and reasonably priced. I use Ixys IXFH58N20 but they are expensive... they are the best though!
Can't find any FQA34N20 over here from reputable sources.

Dave G3YXM

> On 30 November 2018 at 12:58 N1BUG <paul at n1bug.com mailto:paul at n1bug.com > wrote:
> 
> 
>     Yesterday I replaced FETs in my 2200 meter amplifier. Since the
>     FQA34N20 is long discontinued I had no choice but to make a
>     substitute. I chose the FQA32N20C because I know of one active
>     station using them in the same amplifier with success.
> 
>     I notice drain ringing is significantly greater with the new FETs,
>     but maybe acceptable. I have little choice but to run the amp and
>     see how it goes.
> 
>     I also notice the gate voltage decay takes about twice as long as
>     the old FETs. According to the data sheets, turn off fall time on
>     the 32N20C is almost twice that of the 34N20. I suppose that is what
>     I am seeing. I *guess* this may be related to increased ringing, as
>     it appears one side is not fully off as the other begins to switch on.
> 
>     I would appreciate any comments or suggestions, including
>     suggestions for a FET which might leave a longer dead zone at the
>     phase transition. I'd think slow to turn on, fast to turn off would
>     be nice...
> 
>     Alternatively, if anyone has a stash of FQA34N20 purchased from a
>     well respected vendor (old stock) and would be willing to sell some,
>     I may be interested. I've already tried some which originated from a
>     Chinese source and am not interested in going down that road again. :-)
> 
>     73,
>     Paul N1BUG
>     ______________________________________________________________
>     Lowfer mailing list
>     Home: http://mailman.qth.net/mailman/listinfo/lowfer
>     Help: http://mailman.qth.net/mmfaq.htm
>     Post: mailto:Lowfer at mailman.qth.net mailto:Lowfer at mailman.qth.net
>     Post must be less than 50KB total for message plus attachment!
> 
>     This list hosted by: http://www.qsl.net
>     Please help support this email list: http://www.qsl.net/donate.html
>