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N_Cook N_Cook is offline
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Default Mystery motor controller, anyone recognize it?

On 13/08/2017 03:08, bob prohaska wrote:
Does anybody recognize the DC motor controller in the photograph at
http://www.zefox.net/~bob/lathe/motorcontrol ?

There are a few other photos in the same directory showing detail views
of a few items in the enclosure. There are no names, part numbers or
any other identifying marks that I can find on the board. The only IC
visible is a National 741NC, I think the date code reads February, '81.
The Reliance Electric output device is a 701819-X, described as a
rectifier. With six leads it might be a thyristor of some sort, but
web searches haven't confirmed it.

I'm looking for information becasue I'd like to change the wiring
harness to relocate the controller for better space utilization.
Before I mess with it I'd like very much to know how it works,
so if/when I make a mistake there's a chance of fixing it.

At the same time it would be helpful to know what it'll take to replace
it, in case I can't or don't want to modify/repair it. The motor is a
half horsepower shunt wound DC 1750 RPM Browning. Web searches for the
various numbers on the nameplate come up mostly with firearms links, so
I gather Browning is no longer in the motor business.

The application is an old South Bend lathe. Apparently somebody wanted
to wind coils, so they added a soft-starting variable speed drive and
a turns counter. If I kill the DC setup I can always fall back to a
traditional fixed-speed motor but the present setup is very nice and
I'd like to keep it working if possible.

Thanks for reading,

bob prohaska
..



Main board looks more 1970s than 80s with carbon Rs and canned opamps,
if 80s perhaps JFET ones. The lower left white board is later with MO
resistors.
At least the opamps , easy to monitor DC levels and then try a
compatible opamp in the socketted one.