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Help with identifying component?

Nhrafan

Feb 21, 2011
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Can someone help me identify what these components are?

To let you know they are on an output card for a PLC if that matters.

I think I hooked up AC where DC was supposed to go and pop it went.

It blew the green one up into the one above it which is where the impression came from.
Then I noticed the others broken as well.

I believe the green one is a capacitor but I'm not sure if the small black ones are zener diodes or ????????????? AND if they are what is the value for replacements?

Thanks for any help that can be provided.
 

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Resqueline

Jul 31, 2009
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Green capacitor is 10uF 50V. SMD SOT23 parts marked B3 may be (dual) diodes (connected across the relay coils). More parts may be damaged w/o it showing.
 

Nhrafan

Feb 21, 2011
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Thank you.

Well a new card is around $700 so I'm interested in fixing whatever I can.
I have an identical working card so I can troubleshoot and acquire values if necessary.
Any way it can be better identified with a clearer picture or if I include a full picture of the circuit? Anything I can do to help ID it ??
Once I get these replaced I can hook it back up and see what happens...
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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The more relevant information you can give us the better:

1) What happened? (AC instead of DC to power the unit, or to some input?)
2) What are the current symptoms? (Is it totally dead?)
3) Do you have a circuit diagram?
4) Can you give us clear photographs of both sides of the board? (with possibly more later as we identify parts that are of special interest)
5) And as you say, you have another working board, so you can do some comparative testing.

Do you have a multimeter? How good is your soldering?
 

Nhrafan

Feb 21, 2011
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The more relevant information you can give us the better:

1) What happened? (AC instead of DC to power the unit, or to some input?)
Yes, that's what I believe happened. (I was in a rush at the time, hence the mistake made in the first place) The card has an input of 24V DC

2) What are the current symptoms? (Is it totally dead?)
I will have to hook up the unit and check but from what I remember the main cpu states an error with whatever slot this card is plugged into.So yes, basically totally dead at the moment

3) Do you have a circuit diagram?
No diagram that I can find right now, will continue searching though.

4) Can you give us clear photographs of both sides of the board? (with possibly more later as we identify parts that are of special interest)
Yes, will provide best photos I can of everything now and whatever is necessary in future.

5) And as you say, you have another working board, so you can do some comparative testing.

Do you have a multimeter? Yes. 2 The one i'm currently using is Craftsman 81077 How good is your soldering? Gotten me through so far. :)

I will attach photos of the sides of the board and the spec. plate as soon as i can...
 

Nhrafan

Feb 21, 2011
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Pictures of the complete unit and board needing troubleshooting / repair...
 

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Nhrafan

Feb 21, 2011
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Detail of where capacitor exploded and damaged diode(?)

The blue capacitor is one I put in to test but know it's the wrong one so it will be removed when I start working on this...

Next one is where I believe another of the diodes was damaged but not sure how?

Third one is a different angle of that end of the board.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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What I would suggest you do is determine where the diodes are connected in one of those packages (almost certainly a pair of diodes).

Do this by checking the known good board and comparing the results on the bad board.

Even though only one diode has exploded, the board seems to have many similar circuits and I would be surprised if none of the others have failed as well.

What we really need is a picture from directly above and directly below the board so we can see where those diodes are connected. (edit: showing the whole board)

This looks like the relay, so that will help in tracing the circuit. These are a very low current relay, and if these diodes are to suppress the inductive kick when power is removed from the coil, they are probably neither critical nor especially exotic.

edit 2: if the diodes are there for the purpose I suspect, then they are normally reverse biased. Applying AC t the power connection may well have caused them to be forward biased so they became a vehicle for a short circuit across the power supply rails. Note that this brings up the more disturbing possibility that the short circuit current may have passed through the device that drives this board. Does that currently function correctly with the non-damaged twin of this board?
 
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Nhrafan

Feb 21, 2011
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Yes the PLC device itself works great without this board plugged into the main backboard.
It works with the "good" functioning output card of the same type exactly as it should.

I have been able to write programs, upload and download to/from the device and everything it should without this card plugged in.

However, when I plug this card in to the backplane on the plc the main cpu lights the error light and the card will not function with any bit of the program.

I am going to start checking things on the board soon, will post results asap.

Also, I am going to take a few shots of the board from straight on above and below and see how they come out.

Thanks.
 

Nhrafan

Feb 21, 2011
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Here are hopefully some better pictures for you to look at.

1 is overall top shot of problem board

2 is overall bottom shot of problem board

3 is overall top shot of the other board that the problem one plugs into

4 is overall bottom shot of board that problem board plugs into
 

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Nhrafan

Feb 21, 2011
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See attached document.

D23 is where the 24V supply connects (this is where 120V was accidentally applied)
 

Nhrafan

Feb 21, 2011
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Ah, wonderful. This is one of those forums with a ridiculously low upload limit.
Can't attach the 295KB pdf document that lists my measurements.

Any other way this can be done???
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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http://pdfcast.com

And as you might imagine, since uploaded files hang around forever, it is entirely reasonable to put a limit on their size. I know I would.

However, from the "you catch more flies with honey than vinegar" perspective, you could politely ask because the owner of this forum has fine-tuned things like this before.
 

Nhrafan

Feb 21, 2011
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Didn't mean to sound like a dick or anything.
If anyone could tell me how to shrink a pdf or word doc. I would be up for listening??
Otherwise I guess I'll have to get a screen shot program, open the document and do it that way.....
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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OK, the board seems pretty simple. I can see no possibility other than these are dual diodes.

Remove one that looks intact and determine how the diodes are connected.

I would then plan on replacing all 8 of them.

You probably want something with 50V rating and 1A peak would be ample. Maybe something like a BAW56?
 

Nhrafan

Feb 21, 2011
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Here is a screenshot of what I was trying to post before...
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Didn't mean to sound like a dick or anything.
If anyone could tell me how to shrink a pdf or word doc. I would be up for listening??
Otherwise I guess I'll have to get a screen shot program, open the document and do it that way.....

Just post it to pdfcast like I suggested. :)
 

Nhrafan

Feb 21, 2011
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Have you tried going to the site lately?

I don't think it's up?

AH, nevermind.

It's supposed to be pdfcast.ORG
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Here is a screenshot of what I was trying to post before...

Is that resistance? Or is it using a diode test function?

In either case -- I need it in both directions for a *good* diode.
 

Nhrafan

Feb 21, 2011
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Is that resistance? Or is it using a diode test function?

In either case -- I need it in both directions for a *good* diode.

That's in the diode test function setting.
In opposite direction is open.
 
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