How do the pinouts on Exicon mosfets work?

[reiver]

I'm replacing the old T0-3 output mosfets in my Hafler XL-280 with some of the replacement ones made by Exicon.

My old mosfets had three connectors (Source, Gate and Drain). The Exicons have only two:a Drain and Gate connector, but the Source is actually the metal body of the mosfet.

So how do I connect the new Source "body" to my existing wiring? Do I completely insulate the mosfet and simply run a wire/spade from under one of the hold-down screws?


http://www.profusionplc.com/subsites/exicon.htm

[jaycee]

I don't understand what you mean by 3 terminals - from looking at the XL-280 manual (which includes the schematics) it uses TO-3 output devices. The body of these devices is the source, as you have said. They should always be insulated with mica and the source connection made via one of the fixing bolts.

Is it possible that someone before you replaced the output devices with TO-247 or similar flat-pack types?

[reiver]

Thanks, I figured it out.

The stock Toshiba (Hafler) TO-3's have three terminals, one just happens to connect to the body internally, making soldering easy.

The Exicons only have two terminals, but the body is listed in the schematic as terminal "3".

So it looks like you need to run a wire from a screw as terminal "3". Interesting.

[reiver]

Actually it's simpler than that. The Source terminal is a metal strip with that connects to the mosfet screws at either end. Funny what you see when you look up close......

-Bryan

[jaycee]

That's what I thought

Remember the mica insulators, and also the bushings that will insulate the screws from the heatsink where they pass through.

If in doubt, check for conductivity between the metal body of the mosfet, and the heatsink metal. It should not conduct - if it does, there is contact being made.