9 Apr
2013
9 Apr
'13
5:50 p.m.
On Apr 9, 2013, at 20:04, Brian Roth <abacos_98 at yahoo.com> wrote:
Started tearing into the 11/780 and pulled the 11/03
and the RX01 out to clean and test. Looks like the PS is bad in the 11/03. It powers on
and the fans run because they are AC but I am getting sometimes 4.5 volts on the 5v line
and 0 volts on the 12v. I have 34 volts coming out of the diode rectifier. I suspect
switching transistors.
Anyone have experience with these?
Not H780s specifically, but switching supplies in general.
Are you putting any kind of load on the supply? Lots of
switchers don't like running without some minimum load
(I think DEC often specced the minimum load in the
manual).
For low voltage out of the rectifier diodes, the switching
transistors aren't a bad bet. Filter caps are also a possible
culprit, though they're more likely to fail open or lose capacitance.
Check them with an ohmmeter anyway.
- Dave