Tutorials on Logic Probes Got Any Links?

Thomas

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I bought a few logic probes to help troubleshoot some boards. I have never used one before. Do you guys know of any links that might get me started?

Tia
 
I don't know of any tutorials online, but if its anything like the one I got in college you hook up the two clip leads to a +5V source and then use the tip of the pen to test individual pins on IC chips. It basically gives you an indicator of if that pin is a logic high or low. I have never tried to use one on a game board, the states change often. Your better off using a tool like your avatar pic, if you have access to one.

Luke
 
Your right I have been searching google and not much can be found.

Can I use my logic probe with just a switcher to power the pac-man board or would I need more than that?

Small list so far - Nothing major
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1) http://en.wikipedia.org/wiki/Logic_probe
2) http://lawnmowerman.rotheblog.com/logicprobe.html
3) http://talkingelectronics.com/projects/LogicPulser/LogicPulser.html
4) http://books.google.com/books?id=Cv...ouDCDg&sa=X&oi=book_result&ct=result&resnum=4
5) http://www.bkprecision.com/products/docs/manuals/DP21_manual.pdf
 
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Usually you connect it to the same +5V rail that your testing on. If that's a switcher that your using to power your board, then that will work. It doesn't draw much current to interfere with anything.

Luke
 
the trick is knowing what state the pin SHOULD be in. sometimes a schematic shows you a pin is connected to a data line and be pulsing. if it isnt pulsing and you have voltage going into the chip, then you know where the problem is. some are just high and some are low but KNOWING if its supposed to be high or supposed to be low is the hard part. ive tried experimenting on working boards to see the states of the pins, but remembering what they should be for future boards is impossible. i guess one way is to have a working board next to a broken board so you can test then side by side but that means 2x test rigs and plenty of space, etc.
 
Unfortunately, using a logic probe is an art and not a science. Some people like to start at the CPU and work their way out looking for bad chips. Other people start at the clock circuit. And some people just start at random.

For me, I usually start at the reset line on the CPU, at least for the Williams boards. If you get the watchdog to trip, then at least you know the clock and a part of the circuit is working.

I tend to print one of the component maps and a closeup of the section of the schematic I want to look and and then make notes about what I find. If I see something strange, I will hook up a working board and see if I see the same behavior.

ken
 
Good info...

Threshold Setting
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So there is TTL mode and Cmos mode on the probe what is the difference functions for?

Mode Selection
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Mem and pluse is related to those in what way/how?

Now
1) Can I ground out anything on the board probing around?
2) The voltage that i am testing is it a/c or d/c on the board?
3) Can I just run power to the board to use a probe? Do I need anything else? (Just making sure I understand this)
4) Doesn't the scat tell you what the different spots on the board should be reading?
5)
 
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