Diagnosing Series 6+ CCM/CPU Communications Fault

[Sukasa]

I've picked up a Series 6+ PLC (and a lot of cards) recently and am trying to get the unit running, however when I install a CCM into the unit, it repeatedly reports that it cannot communicate with the CPU and shuts down. I don't have access to (nor could I afford) a WorkMaster, or WASI card in order to communicate with the PLC over the DB37 connection.

After a lot of searching I haven't been able to find many answers as to why neither of my CCM (type 2) cards can apparently communicate with the onboard CPU.

The CPU itself has failed parity on the memory board, as the battery had run out before I got it. The sum total of the lights are:

Memory Board (16k logic + 8k register): BATTERY on, PARITY off.
Arithmetic Control Board: RUN off, CHECK on
IO Control: CHAIN OK on, CHAIN PARITY on, ENABLED off, DPU on (set for no DPU)
CCM: BOARD OK off. Diagnostic code is 'CCM/CPU Communications fail'.

What could I do to find the problem preventing my CCM card(s) from communicating with the CPU, and how could I go about fixing them?

 

[Steve Bailey]

The CCM card must go in slot 5 which is the one just to the left of the memory module or slot 6 which is to the left of slot 5. If installed in slot 6 all backplane dipswitches need to be in the open position. Try removing/reseating all cards using the removal/insertion tool to get the cards seated as firmly as possible.

 

[Sukasa]

Oh, I forgot to mention that the POWER light on the PSU is on, and when I checked it with an oscilloscope, all the power rails are steady with no noise.

I'll try seating the card in slot six, leaving slot 5 empty. I've reseated all the cards a few times, as well as cleaned the cards and the backplane (it was covered in a large amount of sawdust prior to being cleaned)

 

[Steve Bailey]

You could try returning all dipswitch and hardware jumpers to default positions.

Also try contacting any GE distributors in your area to see if they still have a Workmaster or Workmaster II gathering dust in a dark corner somewhere.

 

[Sukasa]

Okay, I found the problem - many thanks to you!

Turns out, the DIP switches on that slot were all closed, rather than all open - the manuals I have did not list anything about needing to be all open. That's gotten the CCM working properly - all the diagnostic lights are on and the CPU's CHECK light stays lit.

At this point, I guess I just need to figure out where I can get a copy of the serial version of LogicMaster 6.

 

[Steve Bailey]

Qualitrol has the franchise for the obsolete GE PLCs. They still offer Logicmaster Six software for $525, but their website says they are out of stock.

http://www.qualitrol.com/

 

[Sukasa]

Oof, that's a bit more than my budget right now...

Is there documentation on the CCM protocol available?