1 Nov
2015
1 Nov
'15
11:57 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of tony
duell
Sent: 01 November 2015 18:54
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load
BU208 is
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 the first one I think of (being this side of the
Pond).
This one is a D905.
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.