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dc power supply fets...which, where, why?

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New Member
hey all,

i have a pretty standard zurich 0-15v, 15a max, regulated power supply that has blown fets on the inside of the heatsink. they blew when i crossed the leads. apparently this is not a good way to check for power. they are made by mospec and are tip3055's. no big deal. however, there is a third transistor of sorts on the heatsink that is labeled d880. what is it? what does it do? and what else can i use in this application?

i'm guessing that that's not enough information. i do know that it is a three pin surface mount piece and these three wires do not come from the same board that the wires to the 3055's come from. these three fets are the only things mounted to the heatsink, so they must all be getting very warm.

can anyone help me get this thing running again? i can get the 3055's, but i'm having difficulty with the other piece.

many thanks in advance.


Active Member
(2S)D880 Si NPN 60V 3A 30W transistor.
If the problem occured after shortcut, the current limiter was bad.
You need some reverse engineering to make a circuit diagram...


Well-Known Member
Also, FYI TIP3055 is an NPN, not a MOSFET. That probably doesn't matter if you are doing a direct, same part number replacement.


New Member
thanks a ton

i have the cut sheets for both the 3055's, and the 2sd880's. Now i'll just find a supplier and give it a go.

about the circuit diag...

maybe later.

thanks a ton.
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