In article
,
Bret L wrote:
The transformer will have to be rewound or a new one wound from
scratch, probably cheaper.
The old one can be torn down but if you have a good working set,
carefully removing its power transformer and measuring its no-load
turns ratios and the resistances, as well as measuring the voltages in
set (use a HV probe and gloves, there is lethal voltage here) under
quiescent and full power to dummy load operation, will be useful and
an improvement. You then spec the new xfmr to use the same size lams
and stack of height, and may transfer endbells and hardware over if
it's an endbell type. If it's potted, you will have to depot it. Mc
used tar-regular old roofing tar-as a pottant, be advised. IOW a
mess....
Any competent transformer shop can do the wind, it is not necessary
to pay an overpriced specialist like the guy in Wisconsin as this is a
common old power transformer design. Also, you will probably want to
have the primary turns count asjusted slightly for the modern higher
voltage on today's AC service. When your unit was new common AC was
110 to 117, rarely 120, and now it's often rarely that low.
Bret are you sure that common AC was 110 to 117 and rarely 120 when the
MI200 was new? Is there any hard evidence that the nominal line voltage
was actually lower when the MI200 was new, than it is today? My memory
is that when the MI200 was new, the nominal AC supply voltage was
exactly the same as today, what was different was that there was a much
greater variance of AC voltage levels that one might encounter. I
remember measuring AC voltages at the outlet ranging from 100 VAC up to
135 VAC in the days when the MI-200 was new, today the tolerance around
the nominal voltage is much tighter. I attribute this to the AC supply
infrastructure having been greatly stiffened over the years. Today
distribution feeders are heavier and more numerous and there are more
distribution substations resulting in shorter distribution lines, all of
this makes for a much stiffer system that doesn't require the substation
voltage regulators to be set as high as they were when the MI200 was
new. It is my experience that the highest AC voltages appeared around
the time the MI200 went out of production due to the way the substation
voltage regulators were set to compensate for the losses in the old
distribution system during periods of peak load. Subsequently voltages
have come down as a result of regulatory changes that resulted from the
energy crisis and the availability of more sophisticated control
systems, as well as the improved distribution system.
In any case the stock MI200 transformer provides several optional input
taps to accommodate differing AC voltages, so that redesign of the
transformer should not be necessary.
--
Regards,
John Byrns
Surf my web pages at,
http://fmamradios.com/