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Hi guys,


Yesterday i had a phone call from a customer telling me that he cannot change any value of the user preset variables (Timers, MI's) on the screen because ENTER key is not working.

PLC model is M91-2-R1 installed 4 years ago.


Anyone had this issue in the past? Is there any way to assign the function of ENTER key to another button?

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  • MVP 2023

I haven't, and I would think re-assigning is very dependent on how you have the program set up in the first place .

I also remember someone (I think it was Joe T) saying about one of his clients using a box cutter to press the keys....some people are rough on machines.

Short of getting into the keypad and possibly doing a fix, I think you might be struggling.  And I don't know whether you can just get a replacement keypad, I've never had an M91 apart that far.

Other comments please.

cheers and good luck Kikis,


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Hi guys,


Thanks Ausman and Joe for your reply.

I went on site to check the problem and seems that ENTER key has indeed failed.

Info mode sub-menus couldn’t be accessed because ENTER key function is needed, so I have connected my laptop to the PLC. Pressing the key had no effect on SB53 which was always off.

All other keys were working properly and PLC program was normally running.

Customer and his employees claim that they were always using the keypad gently and did nothing that could have cause damage to the key.

After spending an hour there trying to make it work, I finally decided to get a new 3.5 inch Samba unit and replace the M91.

I use Unitronics controllers for many years now and this is the first time i’m facing a keypad related problem

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18 hours ago, Flex727 said:

You're going to re-write the entire program because of a failed Enter key???

Hi Flex,


My suggestion was to get a new M91 but customer prefers to replace it with a key-less unit.

Customer is always right!


I think re-writing the program in Visilogic won't take more than an hour.

Not so much trouble, especially when you program at night while enjoying a bottle of good Belgian craft beer!

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  • MVP 2023

If they touch that thing a lot I would seriously consider putting some buttons on the panel for frequently used commands such as "START".  I was onsite today working on a touchscreen that failed after 18 months because of multiple daily operator interactions.

I don't care what Unitronics or any other touchscreen vendor says.  Touchscreens are not meant to be frequently touched.  I haven't seen one yet that's made with Gorilla Glass.

Joe T.


@Flex727 - A Samba is SO much better than an M91.  I would do that in a heartbeat.


With all the politicians in the news lately getting in trouble for touching things, I wonder if political correctness is going to kick in and we'll start calling them "Personal Non-Offensive Interaction with Finger Screens"  

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On 11/21/2017 at 7:46 AM, Joe Tauser said:

 I was onsite today working on a touchscreen that failed after 18 months because of multiple daily operator interactions.

I saw people touching the HMI screen like if they were trying to kill an annoying fly.

Usually these people carry old-school keypad mobile phones.


18 months is a very short lifetime though...

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  • 1 month later...

Hey All,

I know this is an old thread, and the OP has come up with a solution, but just wanted to share for future reference.........

A couple years back I had a machine setup with an M91 in an awkward location,  and I went through many plc's, not only through physical abuse, but also direct spray from high pressure water washdown damaging the keypad, after buying unit after unit, Joe T (my distributor), was able to get me replacement keypads so I could take the unit apart, peel off the old keypad and apply a new one, much more cost effective in a chronic damage location.

I don't recall the part number offhand ....... Joe T, care to interject?


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