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Omron sysmac c20 cpu74e

27 posts in this topic

Hi, I am new to this forum. I am a lift engineer. I removed the two EPROMs for the c20 yesterday. When put them Back the unit locked up. I investigated with the test tool and the program seems to be there? Is there a special start up routine? Am I missing something simple? I have the manuals etc any advice appreciated Regards, PCM

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I did not know there were any of these old tigers left in service. Cannot remember I am afraid - gave them away many years ago when Omron stopped supporting them. Hopefully anopher old fella will remember for you.

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Unfortunately, the EPROMS did not carry actual values for timer setpoints. You will probably need to get a handheld programmer to put them back in.

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Thanks. I have a programmer( but no reference list ) I am confused as to why taking the EPROM's should cause this problem. PCM

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Page Down through the program and put a timer value in each setpoint.

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Could you describe better the problem? I dont see any mention here about timers so i wonder why this thread took that way... Does the ALARM light lit? and the RUN light?...

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And you removed the EPROMs because why ????? Was the system working b4 you removed the epoms ? If Yes then why remove.... If the system was not working b4 removing the emproms then simply removing and reinserting won;t fix it. as pfort says, provide more info on the status of the PLC lights, and plugging in a programmer could also reveal error codes. Hey Bob, I think I still have one lying around around somewhere... takes me back to a simpler time.... the c20's are old work horses.

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Hi, back off the road and noticed this thread still alive. I would like to explain the shift in direction on Timer/Counter presets. The C20, C20P and C20K did not carry the Timer/Counter presets and actual values in EPROM. Therefore, if the EPROMs got changed, it was necessary to manually enter the T/C values with the PRO13 Handheld Console. If not , the values were usually some non-predictable hex value, that the T/C would not use as presets. There is always 176 bytes of RAM in a C20 that is used for HR, DM and TC memory areas whether you install a RAM or EPROM memory chip in the User memory socket. This fact bit a lot of early programmers and troubleshooters in the mid-80s.

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Reply to Sleepy Wombat This is the history, 1. Got called to re commission a lift that had been abandoned for sometime . It was missing the two EPROMs. Replaced the two EPROM's 2. Went to a different site with the exact same lift ( which was Working )Plugged in test tool and recorded program onto laptop. 3. Returned to original site uploaded program. This did not resolve the problem 4. Removed EPROM's and brought them over to the site with the working lift and put them into the sysmac c20. Lift would not work. Replaced the original EPROM's back into the sysmac on the lift that was ok. Now it is not working either. My expertise is on Otis lifts. There are not many lifts that use PLC controls. I have contact the original manufacturer and there answer buy a new control panel. I have contacted the local Omron agent and while they have tried to be helpful they are not able to resolve the issue.

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Reply to Jay Anthony I will look into this. Can you comment on the following on the C20 1. Is the program in the EPROM the " operating system" and the program in the RAM the actual program for the device being controlled? 2. I have been through the manuals and cannot find reference to the timers you mention. When the system was powered down ( but battery left in) these timer values where lost? Thanks to all for your suggestions. PM

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Thanks for the heads up..on history... certainly is a trap with those older plc's as Jay eluded to... "Plugged in test tool and recorded program onto laptop." When you say test tool - ie did you upload the program using a C20 hoslink and Syswin/CAPS If so all timer values should be stored in that program ... would no then a simple download fix ? sorry can't be more of a help... been a looonnnggg time since played with one of the inner workings of these...

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By "test tool" I mean the Pro 15 plug in unit. Back in the day the program was recorded on to cassette tape. I recorded it as a sound file and uploaded it to the other sysmac. PM

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W155-E1-2B C500-PRW06 Prom Writer.pdf

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Thanks for the info. I have ordered two Ram G chips. One question though. When I recorded the program originally it would only let me do so if I switches the dip switches from ROM to RAM. So I am unclear as to what I actually saved i.e the sysmac had two EPROMs and no ram chips but I had to switch to RAM in order to save the file. What did I actually save?

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This is when you scrambled the TC presets. My guess is you still have the original program on the audio file.

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New to this forum and wasn't sure whether to start a new thread or not. Decided against it because the issue is very similar and would help someone searching in the future. Anywho... I have the same SYSMAC C20-CPU74E and have a question about the EPROM and/or RAM chip. Old PLC had an output go bad so I ordered a used unit along with the PRO15 handheld programmer. The new unit came with an EPROM. The bad unit has a chip but I don't think it is an EPROM. The chip reads "OMRON BPOK 132 AA 8841 Z07" No UV window either. Is this a RAM chip? If so, won't I lose the program if I remove it? I had planned on uploading and downloading with a cassette but I do not have the cable for the programmer. I thought it would take a standard RCA jack. Can you make one of these cables? I could not find one for sale online. Any suggestions would be greatly appreciated.

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All you need is a two conductor cable with 1/8" audio plugs. Do not buy the red and black ones from Radio Shack as they have attenuating resistors built into the cable. Buy the gray cable instead. You only need one cable as you use either the play or the record but not both at the same time.

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Ruddy short on memory mate! Made you really reduce your code to an absolute minimum.

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Thanks for the response Jay. Yes, I bought a "new-used" unit from the PLCcenter.com. That unit had an EPROM with the sticker over the UV window and the number matched up with one of the numbers that was in the EPROM writer manual that was posted earlier in this thread. The old unit that went bad has a chip plugged in the same socket (not soldered) as the unit with the EPROM but I cannot find any information by searching the numbers on the chip. There is no UV window. I should also point out that both units have the DIP switches set up for RAM instead of EPROM. I didn't know if it was maybe an extra RAM chip or an EEPROM. The program only has 700 addresses so I think that would fit on the built in RAM (this is the expandable processor). Thanks for the info on the cable.

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This is the firmware revision for the C20 PLC. You should be able to use the built in RAM to load the program from the old unit.

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Thanks Jay. I'll get that cable and work on that this week.

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For the CEMCOLIFT OMRON C20 CPU74 - I have the AB MICRO830 as a replacement unit, programmed and ready to go. The I/O numbers are the same, uses the Omron power supply and works great. It even has a power saver (set by jumper) that reduces unoccupied leveling by 70%

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Hello.

I have a question about this unit.  I have broken C20 CPU73E.  Can I use instead of it C20 CPU84E or C20 CPU74E and copy program using C-120 LK201-E -EV1 Host link unit by syswin?

I have a backup from original PLC. Hope there is someone who know this museum models...

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