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Old January 30th, 2018, 09:18 AM   #1
CaspianSage
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1771 A2b Bad Slot

Greetings Friends,

I have a 1771-A2B with one slot not recognizing inputs nor will it turn on any output. It started acting up intermittently on a couple inputs, now nothing.

It is Slot C4- D4 only using C of course. I have taken the chassis apart completely to examine the board and I can see no physical damage.

I also have read out all of the connection points from the socket to the back of the board and the solder traces. I also squeezed (Tightened) and cleaned the socket pins to make sure the card was getting a good connection. I am coming up empty.

I re-soldered the holes that are pass through near pin 12.

Although the card sees an input, the PLC does not in the input image table-

I put a "-1" in the output image table to set all output bits and nothing turns on for that slot. I tested this with several input and output cards and every other slot works.

I know they are somewhat inexpensive on Ebay but I would like to find out where the failure point is.

Any Ideas?

Thank you for your time.... Sincerely!
-
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1+1 = 3 and I never was good at math.
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Last edited by CaspianSage; January 30th, 2018 at 09:22 AM.
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Old January 30th, 2018, 09:31 AM   #2
Contr_Conn
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It's been a few years since I touch these, but I recall that most of the issues were related to the failed chassis DIP switch that caused PLC or adapter to read slots incorrectly.
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Old January 30th, 2018, 11:33 AM   #3
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Quote:
Originally Posted by Contr_Conn View Post
It's been a few years since I touch these, but I recall that most of the issues were related to the failed chassis DIP switch that caused PLC or adapter to read slots incorrectly.

I was wondering about that possibility, kind of shrugged that off as unlikely but now that you mention it that makes sense. I will check that out. Maybe dirty contacts in the switch......

Thanks!
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Old January 30th, 2018, 12:35 PM   #4
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..... Well the dip switch seems to check out ok. Not much to this board so really puzzling.
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Old January 30th, 2018, 01:17 PM   #5
Contr_Conn
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Are you sure that this is not controller or adapter?
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Old January 30th, 2018, 08:13 PM   #6
CaspianSage
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Quote:
Originally Posted by Contr_Conn View Post
Are you sure that this is not controller or adapter?

I am not sure what you are asking... If you mean am I mistaken as to what I have, well interesting question.

I am using a PLC 5/20, I don't think an adapter has an I/O image table.

I first started seeing the problem with an actively running program not registering inputs.
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Old January 30th, 2018, 08:54 PM   #7
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How do you know that 5/20 is OK?
Did you try it in a different chassis?
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Old January 31st, 2018, 09:59 AM   #8
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Quote:
Originally Posted by Contr_Conn View Post
How do you know that 5/20 is OK?
Did you try it in a different chassis?
Yes, First thing did, I have 3 PLC5s and tested with all of them. I changed the chassis out in the working system so I could use slot 4. Test Benching with 2 of the other plc5s in the defective chassis- Its just the one slot that is a problem. No problem with any of the 3 processors in the other chassis.

I want to use this chassis for remote i/o. I can probably get by with out that slot but I don't want to use it in case other slots fail.

Thank you!
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Old January 31st, 2018, 10:51 AM   #9
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Quote:
I want to use this chassis for remote i/o
Just keep in mind that chassis DIP switch setting for RIO adapter in not the same as for the processor.
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Old January 31st, 2018, 10:55 AM   #10
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Solved -Loose Pins in Processor Socket

Went back through all the socket connections for the PLC Slot, first slot in the chassis.

Some still looked looser than they ought to be.

I used a small screw driver and pushed them back together, first left to right then right to left, making the gap between them as small as I could with just enough room to slide the processor into the slot.

All works now but unfortunately I got one set the pins in one slot to tight and when I put the processor back in, it pushed them down into the connector, still makes contact but now I need to fix that or get another socket..

Anyway Problem solved. Loose pins in processor socket.

Thank you!
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Old February 1st, 2018, 10:44 AM   #11
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Thank You!

Quote:
Originally Posted by Contr_Conn View Post
Just keep in mind that chassis DIP switch setting for RIO adapter in not the same as for the processor.
Exactly, I have the settings for RIO - The chassis is repaired now and working fine.

Thank you for your input here,

Although when you mentioned the processor possibly having an issue I knew it was ok, but your post prompted me to check the pins for the processor again and that is where the problem was.

I really appreciate you staying with this topic through resolution of the problem. So a big thanks!

This is one of the best forums on the net I use.
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