jws at jwsss.com
Tue Jun 1 15:35:04 CDT 2010
>> What I did was replace the silicon rectifier diodes with Schottky
>> diodes, which have a much lower voltage drop. Problem solved. Assuming
>> your existing transformer can actually produce enough current from the
>> secondary, that might be enough for you too.
> It would be worth finding out just where the voltage is dropping (between
> the lightly-loaded and fully-loaded configurations). If the RMS AC voltage
> from the transformer secondary is going down significantly, then I would
> suggest that the transformer is being overloaded,and I wouldmn't try just
> fiddling with the rectifiers or smoothing capacitors. Nor would I try an
> external boost transoformer in this case. You don;t want to burn out the
> computer's mains transformer.
> On the other hand, if the secondary voltage is still OK, then I would try
> using schottky rectifiers and/or increasing the smoothing capacitance
> (parallel up some more large electrolytics).
One of my buddies who worked on the Microdata systems, 800's and 1600's
as an FE would not only find an locate problems (in the field), but if
necessary change design elements to fix things. In the day, there were
so many problems that had workarounds in the design that this was a
valid thing to do. RTL and early TTL was all over the place, and if one
were doing component replacement in the field, ad really good FE would
just change things to work.
That said, I would retain what i could with an artifact that I was
planning to operate. However problems with power have the potential to
not only damage the power supply if it malfunctions, but destroy the
entire unit. I would use a modern power supply and retain the original,
restored and functional somewhere for future sale or deacquisition
(trade). Then the unit would at least not be subjected to some of the
bad things that happen if power is not functional.
Fixing the design as tony says is another option, but might be more
difficult to back out than just replacing the entire thing, should you
want to restore it to pristine condition.
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