Rod,

Yours was an early example and I cvan't honestly be sure of the
specification of the 2N3904/ 3906 devices originally fitted.

I do now use the 60V rated ones available from Digikey.

Rick has suggested trying a 2N2222/ 2907 combination?

Regards

Richard

--- In randrdesulfatorforum@yahoogroups.com, "rod.badcock"
<rod.badcock@...> wrote:
>
> Hi,
>
> I have one of the Courtiestown PIC pulsers that has worked flawlessly
> for a couple of years.
>
> .... until now that is!
>
> I'm having problems with the FET drive section of the board, with Q2
> and Q3 (NPN 2N3904) blowing, causing the FET to remain in continuous
> conduction and blowing the fuse.
>
> Any suggestions from here on what might be going on? (seems to be
> related to amplitude)
>
> Rod
>