"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

My R2E4 refused to enter the local editor today.

I could type commands, and see them executed on the main console screen,
but NADA on my terminal. (Well... THAT's not right!)

I have schematics for an earlier machine, and as far as I can tell, those
seem to be the only ones still available. So, trouble-shooting started
with finding out that the RS232 ports DON'T come out the EAF board like
they used to.

I finally tracked the failing port to the BSP board. This sucker has 121
ICs on it, and is the typical "big board" product of the '80s.

Something that can be repaired if you have access to the components.


1488 output driver... that has to be it. I _actually_ had one in my junk
box, but swapping it gave nothing (it was socketed, so no big deal).

I've replaced one so far in our cnc's at work. I added a socket to make the next time a
bit easier.


Checked the input to it while streaming data. No toggle.

Checked the output of the UART that drives it -- TOGGLE! Dang!

I finally tracked it down to a broken feedthrough on the board. I
installed the traditional "patch jumper" made of wire-wrap wire, and it
worked.

Dang! After over 20 years off-duty, I can still do it. Now I have to
find a 20-year-old woman, and see if I can still do THAT!

Good work on the troubleshooting, as to the latter, it is better to remember the stud you
were than learn about the mature man you are now. VBG


Wes

--

OSHA, reversing evolution since 1970.