CPU 928B programs affect EPROM Back up?

Dear All,

One of my staff has just changed the program stored in CPU 928 B without changing the back up EPROM. By changing the SCADA screen output of a spare(future) aeration valve from red alarm to gray indication. the plc system has been a mess from then on..... from all kinds of cards
being replaced DI, DO, AI, CP 5431 and lately the EPROM ....
I just want to confirm if this is the cause of the problem ...

regards,
Fidel

Making changes to the program should NOT affect or damage the PLC hardware.
All of these damaged parts seems to indicate some other serious problem.

I would guess that the problem is caused by something electrical (overvoltage spikes ?). But you cannot rule out other "strange" causes. Is your ground connection good enough ?
I have just come back from a plant where a new PLC was damaged by being exposed to fumes that reacted corrosively with the circuit boards.

Anyhow, I would reset the program to what it was before the problems started. But dont count on that it will make the problems go away.

Dear Mr. Jesper,
Thanks for your advice.....
The two possible problems you identified exist in our plant.
1. The grounding system is corroded due to reaction of the hydrogen sulfide gas (H2S) coming from the adjacent dewatering system where we discharge our sludge cake. The same is true for the cards since all the parts in the pcb board are all black... To cite you an example...
a copper or brass key or coin if left in the dewatering room will turn black after exposure of one hour...
I already suggested to isolate the plc panel from the electrical panel when we opt for an upgrade to S7 system in 2005....

best regards,

Fidel

Have a closer look to DB1, if something changed there you're pretty messing around..

In DB1 are all the cards adressed to the locations in the rack.

Get an old backup and store DB1 in the PLC, maybe it helps

Dear Nak,
Thanks for the reply .....
A neophite with 3 months basic programming background has played around with the program ... Now OB 31 cannot be loaded with the original program since it cannot be transferred as the error says...
we need to edit this OB 31 and retype the BE after we install the BACK ST program ......

best regards,

Fidel