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I need advice from an electric and fundemental guru

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I need advice from an electric and fundemental guru

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Old 09-07-05, 07:36 PM
  #1  
phantomcow2
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I need advice from an electric and fundemental guru

Alright heres the scoop:
About 3 weeks ago I ordered a 4 axis stepper motor driver. It was a Solder yourself kind of hting, but it was at great price, I had read 100% positive comments. I am yet to find a negative comment about it still. It has many features which i wanted, good stuff.
So for 99 dollars i sprung for it.
THis was my first soldering experience, so i got my neighbor who was an ex radar technician to help me out with it.
Before you install the IC chips you have to test to make sure the board is handling electricity properly by testing for 5vDC on a certain place, this did not work.
I replaced various chips and still no luck. This problem has dragged on for a few weeks and is getting nowhere.
The owner offered me an already assembled board for 86 dollars, he says it is tested and ready to go.

I cant say I want to spend another 86 for a board, but it is completely assembled and tested.
I want to offer to return the driver chips which are still in their original packaging (because i never got the proper voltage so i did not install them). He sells replacement IC chips at 15 dollars each! So i will offer to return all 4 of these chips for maybe 20 bucks off. If he accepts, i will purchase that board.
If he does not accept, should i spend the 86?
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Old 09-07-05, 07:40 PM
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Before you do either...do you know why your board is not handling the 5vDC correctly? What's the issue? Maybe we can help solve "that" problem.
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Old 09-07-05, 07:48 PM
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It's really easy to miss stuff on major projects like this. The problem is that you don't have the electronics background or the equipment to properly "debug" it. If you're willing to give it one more shot, grab a multimeter that measures resistance and debug the board thusly:

1: Make sure the power is on. Yes, it sounds silly, but make sure that you've plugged the board in and moved the "on" switch to "on".
Now, unplug the board but leave the switch to on.

You can see where the connections are, so start there. Switch your ohmmeter to measure resistance and crank to maximum sensitivity (1 ohm).
1: For each pin on each circuit element, find the pins of the other elements it's connected to. Make sure the resistance between the two < 1 ohm.
99% of the time this will fix the problem. You'll see a bad solder connection. This will also give you an excellent amount of time with the board to spot solder bridges and shorts.
2: If that doesn't work, identify the elements on the board as "resistor","capacitor","inductor", or "something else." You don't have the equipment to test for "something else":
Resistors should test as the resistance marked on the resistor. Look up the color code.
Capacitors should test as "open", extremely high resistance. (+5k ohms).
Inductors should test as "closed", very low resistance. (< 300 ohms).
(I've made the values here really general, and they'd pass extremely marginal parts, because I really don't think it's the parts.)

If these all check out correctly, then there's nothing you can do there man. Good luck.
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Old 09-07-05, 07:50 PM
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I have no idea why it is not handling 5vDC. Well see here is how it works
You put in 12-44vDC in the input terminal. So i have got a 24vDC power supply that i verified working with a voltmeter.
Using that voltmeter you put the black lead on the negative part of the input terminal, and the red lead on a certain place of the board. It should read 5-5.2vDC.
Of course I get nothing .
This board has two LM chips, LM317 and LM317HV.
One controls voltage to the fan terminal (12v), and one to the rest of the board. I replaced these with brand new ones with no luck still.
I was told it could be any polarized component....
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Old 09-07-05, 07:59 PM
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Thanks redhaired scott.
I have a multimeter from radioshack i bought for this project. Ohms was checked, there is no bad solder connection anywhere. But i will check for the resistance as you say. I like that idea
I went ahead and payed the 86, I have been sitting around with this effing board for 3 weeks and it is the only thing keeping me frm a CNC mill. I just cant sit around much longer before i go nuts .
He said it is a polarized component which has a problem if there is a problem.
When I have htis CNC mill done and i can be at peace I will look into this board and start replacing parts.
Heck maybe I will get it done and have a board ready and waiting for when i decide to convert my lathe too . One rocky road at a time...
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