Omron CQM1H - NOS purchase - ERR/ALM LED On - Program Transfer Problems

[jejump]

Hi Everyone,

I have a customer that needs a CQM1H (CPU51) replaced. They purchased the processor new-old-stock from a source they found online. It arrived in the original packaging and had the safety label around the top of the unit, so it seems that it is as advertised and no need to suspect that it would have problems. I purchased secondhand, a power supply to attach to it and program it from the bench instead of in the machine. The customer also provided me with an SD card containing the project file(s) for the machine. I am able to load the project in CX-ONE (running on Win 7) just fine. My computer has a native serial port (COM1) and I built a programming cable to work with the DB9 peripheral port according to a diagram I found online.

The processor powers up right away with the ERR/ALM continuously on. No other LEDs came on initially, and after a bit of playing around with communications settings, I finally landed the right protocol and my computer seemed to identify the processor correctly. I compiled the source and attempted a transfer to the PLC. I got some failed message (or maybe messages) at the end of the transfer. It did seem to send all of the binary code, it just ended with an error message that I unfortunately didn't write down or grab a screenshot.

Anyway, what I have now is a PLC processor with the ERR/ALM LED on always, I've never seen it in RUN mode, and now after the programming attempt, I'm seeing the COMM LED strobing at about a .5sec frequency (with or without a cable attached to the peripheral port), AND I cannot get CX-Programmer to again acknowledge the processor anymore. I'd like to reset this back to the way it arrived to me, but can't figure out how to make that happen offline. The DIP switches don't seem to cause that effect. I should say also that the DIP switch settings are all OFF except 3 and 7.

Any help is much appreciated!

Thanks,
John

 

[Liam Moran]

A stoopid question maybe, but have you the end cover fitted?

 

[jejump]

A stoopid question maybe, but have you the end cover fitted?

That is not a stupid question and I just learned about the end cover being a possibility 15 minutes ago. Thanks for reply. I haven't looked at the original equipment yet. The customer gave me what they ordered. Doesn't appear to have an end cover. It didn't have a power supply either, so I purchased that myself and will invoice for reimbursement later. The replacement PLC might be missing the end cover like it was missing the power supply. Sounds like the end cover completes some electrical feedback signal on the expansion bus. I had also thought that trying to do this outside of the machine with the PLC missing all the I/O modules referenced in the project, might be causing problems. I may have to do this onsite.

I finally did restore my ability to communicate to the PLC from the CX-ONE environment. I ended up having to turn off DIP Sw 7, turn on DIP 5, then power cycle the PLC. That got me back in!! Now though, I have an error code 0x00C0, which is referring to a problem with the bus. Probably the end cover.

Thanks for answering.
Jj

 

[jejump]

SOLVED (I think): Yesterday, I learned about this thing called an "end cover" that apparently has to be present, or you're going to get the ALM/ERR LED and 0x00C0 I/O bus error message always. This NOS PLC did not come equipped with one. I found one online and zoomed in on the photo of the inside. There's a small PCB in the end cover and I could see a trace on the PCB running from pin contacts A1 to A5. There's a surface mount capacitor there too, but I took a shot an grabbed only a 68Ω leaded resistor and plugged it into A1 and A5. I figure 68Ω is low enough resistance to satisfy the circuitry and safer than a dead short in the event I'm wrong. SUCCESS!! ALM/ERR is clear, and when putting the program in RUN, the RUN LED is now on. Hope this experience helps others one day.


Thanks,
John