# HMI siemens OP73



## MDShunk (Jan 7, 2007)

From what little I've worked with Profibus, my educated guess it that the second dead screen needs the termination resistor turned on. The first item (likely PLC's CPU needs it turned on, the last item in the string (likely your last screen) needs it turned on, and everything in-between needs it turned off. You might also check that both screens don't have the same address. I'm not sure how that would act.


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## MDShunk (Jan 7, 2007)

Forgot to ask... did this system work before, or are you just now commissioning it? Called for manufacturer support? Was something replaced recently? Did this happen all at once, or did something happen before this?


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## eng_bhs (May 27, 2011)

MDShunk said:


> Forgot to ask... did this system work before, or are you just now commissioning it? Called for manufacturer support? Was something replaced recently? Did this happen all at once, or did something happen before this?


With regards to the on/off switch. all switches are correct and the last one is ON. and also the system was working fine few days before and it all happened at once and nothing was changed before except connectors. have anymore idea what could be the reason?


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## MDShunk (Jan 7, 2007)

eng_bhs said:


> With regards to the on/off switch. all switches are correct and the last one is ON. and also the system was working fine few days before and it all happened at once and nothing was changed before except connectors. have anymore idea what could be the reason?


No. Sorry. I'm tapped out. I'm not really a Seimens guy (I'm all A-B), and profibus isn't really something I ever got into. I was fetched up on Data Highway and then went to strictly Ethernet. Someone else will come up with a brainstorm. In the mean time, have you visited any PLC sites? A quicker answer might come from one of them.


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## JRaef (Mar 23, 2009)

99% of the time it's a bad Profibus connector termination.


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## Jlarson (Jun 28, 2009)

I'm not a Profibus expert either but I check what MD listed then pull out a scope and probe around a bit and mess with the terminations to see if one is "flaky"


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