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Author Topic: ud1212-R cable and pen?  (Read 27440 times)
bernard
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« Reply #45 on: March 03, 2010, 02:53:41 PM »

Always test in "steps". (Sorry if I am saying things you already know or does not apply - I am not sure what is your current state). 

Random thoughts:

Put your multimeter to make a "Beep" when both probes touches. Warning: Never use that "mode" when stuff are powered.

Test your cable first following your diagram.  Also test your cable connected to the UD (but still unpowered) and see that the signals are propagating to the board. Check that no two wire "cross" (each wire goes to one and only one pin).

Now to test when powered stuff: 

Put your multimeter to "DC" Voltage -- put the black wire (also named COM) to "ground" or "negative voltage" (but if you do it in reverse it is OK, the reading will simply be negative, no problem there)y. 

Test your power source alone, then test the cable with only the power connected.

Connect the board, see if you see your power going onto the board.

NOTE: on the UD controller board, there are two 1 cm/square areas that are made of copper which you can use for "ground" (put the black wire there).  Then just put the red wire at various areas on the board and look at the reading.

Warning: when stuff are powered, always watch out to not make a "short" with your probe. Always find places to place your probe that are "safe", always double-check everything you are doing, just to be on the safe side.

Notable things to check: 

Check that the power goes through the main power switch.

On the board, you should see 5 volts at one point, near the IC102 (a black square thingy near where it says "SERIAL NO" with 2 pins). This is the 5v regulator (if I recall correctly). (it converts (or regulates) the 9v-12v input voltage to 5v).

On the board, you will see small copper "circles" which does not seem to have any purposes. These are "Test Points" (used to "QA" the board by a machine or for a technician).  They are often named "TP00" or "CP000". Those are nice to test.

hope that helps!  Smiley
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rbritt
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« Reply #46 on: March 04, 2010, 12:30:17 PM »

Brilliant, I will give all of this a try tonight Cheesy Thanks for the advice!
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rbritt
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« Reply #47 on: March 10, 2010, 11:44:55 PM »

I've had a bit of a play with my multimeter now, built up some confidence measuring the voltage on batteries and doing a continuity test on everything from cables to spoons in the kitchen drawer and I think I've got some of the basics now Smiley I checked the cable and it looks like I'd soldered the connections ok (though I only have the power connections - pins 7 and 8 - soldered up).

Next I measured the voltage on the power adapter I'd been using. On the outside the adapter it clearly states an output of 12v with up to 1000mA output DC. Measuring the voltage on the adapter (without it powering anything) gave me about 20v! Is this normal? Is the adapter giving out too much juice which could have harmed the wacom?

I'll do more measurements soon to explore more. I also have a variable voltage power supply I'll play with. This is sort of fun but I really hope I haven't accidentally fried anything on that wacom by plugging it in before doing all of this!
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bernard
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« Reply #48 on: March 12, 2010, 04:10:31 AM »

When a power supply is not connected to anything, it does not have a "load" and its output can be a bit wacky (not always, but the cheaper ones are like that). It needs someone to pull some power to function correctly.   Recently I had the same problem and I strapped two 6v light bulbs together to have a 12v load to test the output.  Some multimeter (very rare) have a "load" function, but I am pretty sure you do not have that.

So for your case, it might or might not be normal: 20v is a bit high indeed **if it was connected **.  I've seen many universal adapters (with selectable voltage output) that outputs more than advertised -- most of them were a bit old (over 10 years), so that might explain it(?).   Is your supply "new"?

You can at least test if the "polarity is good" before (sending the positive and the negative (ground) in the right pins).  Voltage reading should be positive, try reversing your probes, it should be negative. (even if 20v)

So I guess, your only solution (unless you have some way to make a load) is to connect it. Prepare everything, take an inspiration, and connect it to the board and test it (quickly) before disconnecting it. I think you already connected it before, right?  So probably if there was something to blow, it is blown already. Smiley

Some more electronic theory: If your supply is 1000mA and you plug it to a device that wants even more current (over 1000mA), then the voltage will (typically) start to "drop" to "compensate". On higher quality devices, internal power regulators should normally "shutoff" under a certain voltage as a "security measure", but it is not always the case.

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