repair

Discussion in 'Technical Repair' started by krc777, Mar 18, 2008.

  1. krc777

    Thread Starter Member

    Mar 18, 2008
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    Hi-
    I have a Wacom digitizing tablet, about 10 years old. It worked fine, was stored well for about 5 years, still looks like new. So the other day I pulled it in to the power source, smelled a burning, quickly unplugged it and now it won't turn on. So, I understand I have fried it in some way. I called Wacom to ask for help/repairs and they just said it's 10 years old buy a new one. Can I repair this? I've opened it and I can see just past the power connection there is a burn mark on the case. The rest of the panel looks okay? Any chance of repair?
    Thanks for any help or thoughts on this.
    k
     
  2. techroomt

    Senior Member

    May 19, 2004
    198
    1
    not much to go on, but i can recommend following typical troubleshooting process. you'll need to remove the damaged board for a good eyeball and ohming out. something likely shorted out, or component failure caused an excessive current draw on the power source lands. with some luck a fuse blew down line. ohm out the load to see if there is a short, or extremely low resistance. let us know what you find.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    The first things I would suspect are any electrolytic capacitors in the power supply section. They go bad over time. Look closely at the tops of the caps; if you see any that are bulged, have tiny holes or the tops blown clean off/open, you've found a problem.

    There were a few Asian companies that made (and are still making) electrolytic caps with electrolyte that is far too concentrated. This results in early failure of the caps.

    If you want to restore it and have it last a decent length of time, replace ALL of the electrolytic caps with new ones of recent manufacture from a reputable distributor, like Digi-Key, Mouser, Newark, Allied.
     
  4. krc777

    Thread Starter Member

    Mar 18, 2008
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    I don't see anything like what I am used to recognizing as a fuse. When I open up the tablet inside it looks a lot like this: attached photo. Just past the input area is a small black chip and this is where the burn occurred.[​IMG]
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Well, I found the user's manual in PDF format for your tablet. Unfortunately, I didn't find a schematic, but I did find out that it's powered by either your USB port or keyboard/mouse port.

    Looks like the board is all SMT (surface mount technology) which is going to be tough for a hobbyist to troubleshoot/repair, particularly without having a schematic to refer to. It's likely that the PCB is multilayer, which will make things even more difficult.

    Can you post a high-resolution photo of just the area where the burn occurred? Say, a 2"x2" or 3"x3" area?
     
  6. krc777

    Thread Starter Member

    Mar 18, 2008
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    I have a photo of the board with the burned part circled in yellow but I can't get the insert picture here to work. :>(
    Thanks so much for your help.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    You probably can't post it because it is too large in Kbytes.

    Perhaps you could host it somewhere like Flikr or Photobucket or (preferably) on your own ISP's website, and then post a link to where it is.
     
  8. krc777

    Thread Starter Member

    Mar 18, 2008
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    Okay, I posted it to my blog. http://kristinecampbell.blogspot.com/
    If you click on the photo of the board it will enlarge and the 'burned' part is located near the bottom of that screen.
    Thanks.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    I see; looks like "ZD102" is the reference designator. The "ZD" indicates to me that the item is a Zener diode; of what voltage would be tough to tell exactly if the numbers are burned off. The three IC's that I can see are all 74HC4051; CMOS multiplexers/demultiplexers; they have a recommended operating range from 2v to 6v. The little tan rectangles with labels like "C213" are ceramic capacitors, and are connected across the IC's Vee/GND and Vcc/GND pins.

    Since the ref des ends in "102", that tells me there is another Zener diode somewhere else on the board. See if you can find "ZD101", and read the tiny lettering on it.

    It looks like there was something else on the lower left corner of the white-outline rectangle inside the circle that is now a blob of solder. Can you get a better close-up of just that area?
     
  10. krc777

    Thread Starter Member

    Mar 18, 2008
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    I posted two more photos on the blog. I did find one ZD101 in the middle of the board. I circled in yellow. I wasn't sure what tiny lettering you meant by the ZD101 so I hope you can see what you need on the photo.
    The only white triangles I can see, one has 10 next to it and the other a 1.

    Thanks!
     
  11. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
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    You do have a fuse .... labeled F102, near the switch on the right hand side.

    I suspect anything in the 100 series is the power supply ... so I would investigate that area first.

    I think he means the lettering on the component themselves.
     
  12. krc777

    Thread Starter Member

    Mar 18, 2008
    11
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    Could you explain this a little for me? If it is the fuse how do I repair that? And what does 'anything in the 100 series' mean?
    Thanks.
     
  13. krc777

    Thread Starter Member

    Mar 18, 2008
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    The ZD101 has the numbers 512 on it.
     
  14. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    100 series is 100 - 199.

    F102 is a fuse close to the switch
    C10x, next to the fuse ...

    It's typical for the "power supply" parts to have the same series of numbers. Other functions will have different series.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    OK, the ZD101 marking in the middle of the board is offset from where ZD101 actually resides, as there wasn't room to put all of the markings where the parts actually go. If you look at the attached, ZD101, you'll see the actual part of interest circled in red, down near the single blue rectangle (which is an inductor.)

    What are the numbers and/or letters written on top of ZD101? [you said 512]

    You'll probably need a magnifying glass to read them. [perhaps you didn't!]

    Note how ZD101 looks physically - a three-legged critter. ZD102 looks like it was blown in half!

    It looks like your tablet gets it's power via pin 3 of the connector next to ZD102. Is there a power supply/wall wart in addition to the RS-232 connector?


    (ETA)
    512 is a code for a Philips PZM5.1NB2 which is a 5.1V 0.3W Zener diode. I suggest that it's likely that both ZD101 and ZD102 were the same, but we don't know for certain yet.
    See this page:
    http://www.tkb-4u.com/code/smdcode/smdcode5.php
    Very handy reference page begins here:
    http://www.educypedia.be/electronics/datacomponent.htm
     
  16. SgtWookie

    Expert

    Jul 17, 2007
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    Wow, I guess I took too long - lots of exchanges lol
     
  17. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    It sounds like the power supply had an issue and sent too much voltage to the tablet. You might want to measure that supply under load before using it again.
     
  18. krc777

    Thread Starter Member

    Mar 18, 2008
    11
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    I know I used the wrong adapter. I used a 15V and it was too much. Of course I didn't know this until after it burned.
    Yes. the ZD101 has 512 written on it.
    The first photo I posted that showed more of a close up of the ZD102 also showed the power supply cable. That cable has a connection to the serial port of the PC and at that same connection the power supply to the outlet. I don't really understand the 'Is there a power supply/wall wart in addition to the RS-232 connector?'
    Thanks!
     
  19. krc777

    Thread Starter Member

    Mar 18, 2008
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    Okay, just read this is wiki: A linear or (rarely) switched-mode power supply (or in some cases just a transformer) that is built into the top of a plug is known as a "wall wart", "power brick", "plug-in adapter", "adapter block", "AC adapter" or just "power adapter".
    So, if I understand this correctly I have a wall wart, ie. plug in the PC connector.
     
  20. krc777

    Thread Starter Member

    Mar 18, 2008
    11
    0
    In further reading, can you tell me if I have this right, a Zener diode allows for the flow of current in one direction unless the power source is too much, as in my case, and then the flow is halted or pushed backward causing the ZD to blow. If this is true, if the ZD is repaired will the tablet be back in business??
    Thanks for all the help.
     
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