MainBoard Problem

[Hussien]

I Have this Mainboard that is running a 20,000$ machine and it need repair. The question is where to start I mean how to know where is the problem?? is there any restricted instructions to do that ?

I have the following equipment in my room:
1- Oscilloscope DS1054z.
2- Amprobe AM-510 avometer.
3- Power-Supply.
4- the rest tools for soldering and etc.

I did changed the capacitors I thought it get dry from the temperature raising of my area (Iraq).
the board pictures and a short video can be founded here:
http://www.mediafire.com/download/dspyerbtj3hodr5/MainBoard+Problem.rar

if any one has idea to do that and has a manual or textbook to learn that plz send it to me at: hussien_nassir@yahoo.com
Shown me the way and I will do the rest....

Best,
# Ni@C

[LA7SJA]

Even if I couldent open you rar archive, my first question would be what are the symptom(s), what have you messured and done so far. If and when I have the time I would try to open the rar file and see what you have sendt.

Johan-Fredrik

[Hussien]

I sent the picture of the board and a short video of it in the machine.

I try to turn the machine ON that morning it just shown nothing on the screen. the fun is not working too.

The time I meaure the Vin, Vout of (LD1086V25) the fun start working. I changed the capacitors at the power plug side on the board(you can see that in the pictures) till now. nothing else.

I hope there is other instructions to do measuring other things, but I am begineer and donno what to do... 

best,

[SkyMaster]

I try to turn the machine ON that morning it just shown nothing on the screen. the fun is not working too.

The time I meaure the Vin, Vout of (LD1086V25) the fun start working. I changed the capacitors at the power plug side on the board(you can see that in the pictures) till now. nothing else.

I hope there is other instructions to do measuring other things, but I am begineer and donno what to do... 

This main board, it is coming from what?

The 10-pin connector, in one of the corner of the board, seem to be the power supply connector, is the power supply functioning correctly? It seems that there are various voltage on that board (I see 5 volt and 21 volt near this 10-pin connector). Checking the power supply should be your first step.

Also, one of the wire going to this connector appear to be damaged.

[fluxcapacitor]

which capacitors did you replace. Replace all the sam young caps , the one on the left is lifting its lid, its gone.

[Hussien]

The board is coming out of a "DGI printer" I replaced all the capacitors. three of them .


BTW the power connector is fine, the red led is ON when it is connected to the main power. but is the past when the main power is on there is that buzzer beebing giving an indication that the system is loading now it is dead.

I check the buzzer and it is fine it works.

BTW which wire seems damaged?? which pin of the 10 pins (can u circuit it on the pictures i sent? )

[Hussien]

I think the image can demonstrate more information ....

[Richard Crowley]

Can you get a service manual for the machine?  What is the model number of the machine?
Do you have access to another (functional) machine?  (To establish "normal" voltages, signals, etc.)
What does the power supply module say?  Does it give the rated voltages and currents for each bus?
You should at least start with the power input connector. Measure each pin (vs. ground) to see if the supply voltages look right.

[Richard Crowley]

I think the image can demonstrate more information ....

Why did you replace those capacitors?  Did the original capacitors look bad?  Did you test them?

Please measure the voltage on each pin of the power input connector and tell us what you see.

Shorting pins on a transistor (or regulator) like that is very dangerous to the circuit. You may have caused more harm.

Identifying the numbers on those transistors (or regulators?) would help understand how they should work.  And measuring the voltage on each pin will reveal much useful information.

Yes, it is possible that one or more of those integrated circuits could be damaged. But there are many other more basic things to check before you get to those. 

The most common problem for the symptoms you report is a power supply failure.

[Jeroen3]

Things to measure:
- There are measurement pins next to the caps. Do the voltages printed there correspond with the measured value.
(beware of common earth when measuring with scope)
- There are many bypass capacitors, you can use these to measure if the Vdd lines go all the way around the board. Either Vdd25 or Vdd33. (2.5 or 3.3v)
- There are 2 usarts, does the scope see anything happening on those lines?
- Those 3 chips next to the large qfp are rams and flash, they need clock, can you measure any clock? (refer to the datasheets of the parts)
- I assume the socketed chip is ROM. Should also need some clock.

The large ATX-ish power supply connector. That goes to an external supply? That still ok?

And, that is wrong with this wire in the connector?:
https://db.tt/H8rDPNiI
By the way, the earth is disconnected in the image.

[SkyMaster]

BTW which wire seems damaged?? which pin of the 10 pins (can u circuit it on the pictures i sent? )

And, what is wrong with this wire in the connector?:
https://db.tt/H8rDPNiI
By the way, the earth is disconnected in the image.

Hussien, as Jeroen3 pointed in his post, it is the wire going to what appear to be pin 7 (the black wire between the yellow and green wires).

[wasyoungonce]

I think its all from a DGI VT3 large scale printer/cutter ...the main board.  However, I suspect the fault is in the power supply to this board.

http://www.digiprint-supplies.com/vtiv-62-main-board.html
http://www.digiprint-supplies.com/vtiv-62-main-board.html
http://www.digiprint-supplies.com/dgi.html?limit=30
http://www.machine-spareparts.com/DGI_Printer_Parts.html

[Hussien]

I am Really happy to read ur help guys 

Richard Crowley/
no i dont have the service manual of the machine, How can I get it?
I connect the board to another machine "DGI Printer" and it still not working means the power plug of my machine is fine.
I changed the capacitors cuz I measured the value of them and it was showing less, some of the capacitors didn't show any value when i test it.

the part number of the Regulators is "LD1086V25" and "LD1085V33"(Left, right respectively)when the short the left one the fun start working.

I think the power is fine I mean the power goin' in the board cuz the SMD-LED light up indicating that it works.
although I will check the voltages on the plug comin into the boards... and feed u back.

Jeroen3/ I get the idea and I will check it as u suggested. 

[Hussien]

Plz Find the attachment,

[wasyoungonce]

You just cannot short across those legs.  They are low dropout regulators, you just shorted the output to ground.  This probably won't damage them as they will probably overload/shutdown, but this is not the thing to do.

You should be measuring their input legs are the correct voltage (where every they get power from) and their output legs are correct, according to their spec sheets.  Google their part numbers for spec sheets.

Some more information on the model number or printer, better images etc might help.