6 Jun
2010
6 Jun
'10
11:21 a.m.
Philip Belben wrote:
That sounds very low indeed. I wouldn't expect a
transformer
secondary to drop below rated voltage with only half load on it! Are
you sure you haven't got a shorted turn somewhere?
I agree with Tony that you should do some more tests to see if there's
something wrong with the transformer or rectifier. For a start, look
at the secondary voltages and current drawn from the supply with all
the secondaries open circuit. Excessive no-load current is a
reasonable indicator of a shorted turn.
If you eventually do need to upgrade the power supply, could you fit
just one switcher in the cabinet with that transformer? Use it for
the 8V line, and keep the old PSU for the rest?
Just a suggestion: I am running a Pentium III system which probably
needs its internal
power supply fixed. When I attempt to boot the system with the 3 hard
disk drives
on the internal power supply, the system crashes. I now use an external
power
supply for the 3 hard disk drives and the internal power supply for
everything else.
When I run my PDP-11/83, the 3 ESDI hard disk drives probably place a strain
on the internal power supply. I use the same solution and run the 3
ESDI drives
on an external power supply along with a fan for each to keep them
cool. As it
happens, I purchased about a dozen ESDI hard drives about 15 years ago when
they were no longer in demand, but still plentiful. I seem to remember
that they
arrived 4 in a box with additional hardware to support a RAID
configuration of
some kind. Each box had its own power supply. My requirement was to use
just the ESDI hard drive for the PDP-11/83 on a Sigma RQD11-EC ESDI
controller, actually 3 hard drives on the controller. The power supply
and the
fans in those boxes are still in use after 15 years with one power
supply now
used with the Pentium III to run 3 ATA 160 GB drives as opposed to the
original 4 * 600 MB Hitachi ESDI drives that were in each of the RAID
boxes.
Its amazing how the same solution solves the problem on such different
hardware.
The VT103 PDP-11/73 system that I run once a decade also uses an external
power supply to run the hard disk drives.
Jerome Fine