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Old 03-26-2013, 01:35 PM
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bluebee bluebee is offline
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Originally Posted by 540iman View Post
There is only ONE mosfet in the FSU and I would forget about trying to replace it even if you had one.
I'm not sure if there are one or two, because I broke one in half, and I don't see the other one (yet).

It's an epoxy resin filled with silica. It will come off with DMSO at three atmospheres or so. Sometimes a soak in DMSO for a couple weeks will make it peel off. This will also soften the PC board though.
Without soaking for days in DMSO, there's just no graceful way to get that epoxy off that transistor (cut in half by accident, in my photo below).

Originally Posted by 540iman View Post
There is only ONE mosfet in the FSU
How did you know this? It "looks" like there are two sets of three closely spaced holes - so how did you know there was only 1 transistor?
Note: I think it 'could' be that there are actually two; but I haven't 'found' the second one, if it exists.

Elsewhere, it was said:
the spacing of the three holes is consistent with a TO-220 transistor pair, and if it's a linear pass regulator like it appears to be, there needs to be a big transistor somewhere. Also, of course, there is the heatsink.

That IC is only control logic, it just takes some mystery input signal and produces a variable voltage for the transistor base. Those two transistors are doing all the hard work. BUT, if you want to replace the device with a retrofit one, you need to know what that mysterious input signal is.
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Last edited by bluebee; 03-26-2013 at 06:52 PM.
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