6 Jun
2010
6 Jun
'10
5:54 p.m.
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?
My experience is that a single shorted turn in a mains transformer will
cause enough primary-side current to be drawn to blow the fuse. Of course
that's assuming there is a primary-side fuse -- but if there isn't there
darn well should be :-)
Still, it can't hurt to measure the primary current with no load on the
secondaaries. If you have a wattmeter, masure the power consumed by the
trransformer with no secodnary load (note that this is _not_ the product
of the primary corrent and the mains voltage, they will not be in phase).
If there is significant power drawn on no-load, then suyspect a shorted turn.
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.
I should have read on before writing the above :-)
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?
My personal view (if I had such a machine) is that as the originial PSU
wasn't a switcher, you shouldn't use a switcher to do any form of upgrade
or repair. But it's really up to you.
-tony