old GE 90-20

Hi All,
Trying to help a customer out with a 90-20 plc, brick. Very strange operation. It is connected to a Maple systems hmi, and it shows when power is applied after resetting machine (ready to run). Pressing the start switch, machine runs normally. (Machine is a small labeler with a Camco rotary table and Kebco clutch brake). In random time periods (from 10 seconds in run to over 25 minutes this am, the plc loses all i/o leds except the power, runs for 2-3 seconds, leds go out, like resetting itself from a short circuit. (There is an eprom with the program onboard, maybe it reboots that way). At this point, the estop can be pressed cutting out all output power, but sometimes it stops flashing, other times it continues until totally powered down then up again, where at this point it acts as if nothing happened. It can be started again, may run for a while, may not. I cleaned all of the spring pins on the header strips, all seem fine. While running or flashing I monitor 120VAC input at all times and 22VDC on the dc power output at all times, whether the plc is flashing or not.
I am thinking plc internally somehow, and am wondering if this is the next move. Found one on Ebay, unless someone out here wants to get rid of a working unit at a reasonable price.

Any ideas? Been over 15 yrs since I even saw one of these, my software is long gone, even that was the DOS version.

Thanks for any suggestions,

tommy23t

As far as I know you'll need Logicmaster software to program this museum piece. I agree the problems are probably an indication that the PLC is on its last legs. It would be a better bet to replace it with something current rather than try to find a replacement. You might be able to convert a Logicmaster file to a VersaMax micro. If you can get a copy of the Logicmaster file I can try to convert it for you.

Thanks for the quick reply. The problem now is that the customer is on a tight budget, don't have to tell most of you about the plight of manufacturing in NJ, or the US. I know they don't have any program on this, we had to search to find the wiring diagram (at least one that was close). The plc is the easy part, the display/ hmi is always the bugger, for the few functions and settings they need, usually cost more than the plc. Maybe will see if the Unitronics Jazz will do, used these in the past for them.

Thanks for the offer, it is appreciated.

tommy23t

I don't see any reason why the Maple HMI won't work with a VersaMax Micro. The program should convert rung for rung from a 90-20 to VersaMax without any changes in address. Depending on the VersaMax model reuired to accomodate the I/O count you could wind up using the same cable. Some of the VersaMax Micro models have the same 15-pin RS485 port as the 90-20 and they both use the same serial protocol.