The power supply causes the intermittant fault in these 20 year old PLCs.
You can replace the PS board TOMORROW without having to download the software.
Two week satisfaction guarantee or FULL REFUND. Two year warranty.
Flat rate including OVERNIGHT shipping $1200.00.
If you buy a used one the PS is partially worn-out.
You would have to download the software, then sell your intermittant one on eBay.
How long did your last used one work?
I'm an Electrical Engineer, not a salesman.
I replace all of the components which gradually wear-out, not just the one which is bad now.
You can receive a exchange PS tomorrow for:

PC-0984-780, PC-0984-785, PC-D984-785, PC-E984-685, PC-E984-785,
PC-F984-785, PC-K984-785, PC-L984-785. Two week satisfaction guarantee. 

call (804) 252-0464 any time

or e-mail  repair@videodisplayunit.com