Re: PLEASE HELP. how can i test the circuit board of a keyboard to map the matrix without the possability of fyring the board??????????


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Posted by Tiger-Heli on 4, 2000 at 7:36 AM:

In Reply to: PLEASE HELP. how can i test the circuit board of a keyboard to map the matrix without the possability of fyring the board?????????? posted by charlie on 3, 2000 at 9:01 PM:

: i didnt understand what REG told me so ill try again. i dont want to fry my circuitboard and since this is my first project i dont want to screw it up. i know if i test the wrong 2 soder points in the matrix it will fry the board. i need to map the matrix but im scared of frying it. if i use the multimeter, and i get a current, does that mean it is a functon and will register a key. if i dont get a current that means it wont be a function of a key. do i have this correct? i want to use the matrix test to find out the keys and dont want to use the flimsy part with the spagetti like paths. please help and put it in a langusge so i can understand . thank you.

Again, my article at www.mameworld.net covers this in detail, you really should read it. What isn't covered is this: All mapping is done with the keyboard disconnected from the computer. You can't fry anything this way! On the multimeter, you want the ohms setting (which measures continuity) use the highest setting you have available (i.e. 10K ohms, not 10 ohms). On this setting, you will get full scale deflection when the multimeter leads are touched together. Start with the circle (on the flimsy) under the L CTRL button. You want to test with one lead on the circle contact points on the flimsy and move the other lead down the input header on the keyboard circuit card. On two of the contact points of the input header, you should get full-scale deflection of the needle. These points are the row and column inputs for the matrix for the L Ctrl keys. By tesing this way, you can reassemble the keyboard and test for ghosting using keyhook (or similar program, see the downloads section, this site) once the matrix is mapped out.

BTW, your thoughts about current are not correct. Also, you can't really fry anything by testing the keyboard circuit card. You can fry the COMPUTER MOTHERBOARD if you don't solder carefully when you connect the ribbon cable to the keyboard circuit card!

Good luck with your project!


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