Testing H7864 (MicroVAX II) PSU With No Load
ard at p850ug1.demon.co.uk
Sun Nov 1 12:54:23 CST 2015
> That said, it's possible that there may be an auxiliary linear regulator in there. That's common
> for additional outputs with modest current needs, especially in older designs where the
> switching circuitry takes a lot of individual components. A TO-3 can isn't what I would expect
> to see in a switching-only supply. In other words, that particular transistor might be the pass
> transistor of a linear regulator.
There are plenty of suitable chopper tramsistors in TO3 packages. The BU208 is the first one I
think of (being this side of the Pond).
I've just looked up the printset for the 11/730 PSU (mine will be on the bench soon I hope...). There
are, as I said, 4 SMPSUs in there, 2 of them use choppers in TO220 packages, the other 2 use
choppers in TO3 packages.
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