1 Nov
2015
1 Nov
'15
10:54 a.m.
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.
-tony