[Coco] RS-232 Pak voltages

[Gene Heskett]

On Wednesday 08 April 2015 03:23:39 K. Pruitt wrote:
> Perhaps somebody knows this off hand:
>
> What should the voltage be on the DTR and RTS pins of the Tandy RS-232
> Pak?
>
> I'm reading 1/10th of a volt.  Is it supposed to be that low?  I'm
> fairly certain I am measuring it correctly.  Though I won't rule that
> out as a potential issue.

The little psu/convertor is duff, or the tx side (mc1488/mc1489 I can 
never recall which is which and both are easily blown by a long printer 
cable and a nearby lightning strikes emp.) driver chip is blown. If you 
have an MPI, and the convertor is duff you can remove the convertor and 
feed it from the MPI.

But, I'd check the output of the convertor first, just in case one of the 
mc148x chips is blown.  They have not historically been a chipset noted 
for longevity in an abusive situation.  I don't recall that it makes the 
full 12 volts in both polarities, but anything above 8 volts is 
generally usable.

> Thanks

Cheers, Gene Heskett
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