[GreenKeys] MCT S-100 Serial board - Ever seen one? CL and/or RS-232?

[drlegendre .]

Ok, I can clear-up at least one or two things, here.

On Mon, Dec 22, 2014 at 7:06 PM, Steve Garrison <steve.n4tty at gmail.com>
wrote:
>
>
> And that board really looks like it had a major heat problem on the lower
> left at one time. Can tell if it was the power buss that was involved, but
> pin 1 & 51 were +8 volts unregulated and pin 2 was +16 volts while pin 52
> was -16 volts, again both unregulated.
>

The browned areas of the board are where the +/- 12V Zener shunt regulators
are placed. At some point, prior to my ownership, it seems that those zener
regs burned-up and were removed from the board. As received, those patterns
were unpopulated - the parts were simply cut off.

I cleaned up the patterns and replaced the parts with high-wattage Zener
diodes and appropriate biasing resistors. The board how has +12 / -12 / +5
regulated supplies, as originally built. And no, I have no idea why those
zener reg parts were burned up.
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