> -----Original Message----- > From: cctalk [mailto:[email protected]] 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 > > > > 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). >
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. >
