os008
12-11-2007, 03:32 AM
Hi there,
I'm an Aerospace Engineering student, but i'm a bit weak in Electronics, as we only study the basics, we mainly study Mechanics (Structure, which is Mechanical Statics, and Aerodynamics, which is ... Gas Dynamics :P)and Thermodynamics.
Anyway, i got the pot thingie, and i also have an Analog AVO-Meter that has a problem with the Resistance measurement part of it, but it works perfectly for measuring Volts and Amps, i made sure of that through a lot of testing, so i can't measure any resistances.
I connected the positive pole of a 12v 18Ah (lasts 1 hour if 18A are drawn from it, less if more are drawn) battery to the first outer leg of the pot. Then took the second outer leg and connected it to the negative pole of the battery, and then set the meter to measure DC voltage, and measured the potential difference across the first outer leg and the middle one What i noticed was that the the meter read 5v, and 7v across the second and middle, when i turn the screw, it decreases and increases depending on the direction, so the pot is working :P.
Now, like i said, the resistance measuring part of the meter is not working, or working but doesn't provide anything but an indicator if there's a short or open circuit, and it says 200k Ohm when at idle, even if i try to adjust the skew (forgot its exact name). So i measured the resistance across the 2 outer legs, result ... shorted (0 Ohm), turned the screw all the way to the other direction, result ... shorted (0 Ohm), adjusted the range, same result on all ranges, even on 1 Ohm or 1 MOhm accuracy, measured across the outer and middle, same result.
All that was on the multi-turn VR, i got another VR, but single turn, i tried to measure the resistance across the 2 outer legs on that one, and it didn't give me a 0 Ohm, but 'a' resistance, which doesn't change neither by adjusting the range, nor by turning the screw.
Now my question ...
why does the resistance get SO hot when i try the 3 legged connection which works well?
why is the first VR always shorted, and the second gives 'some' fixed resistance?
why is it working on 3 legged connection only?
also, how can i make a 3 legged connection for this card's (HD 3850 or 70) volt-mod please?
note: i can't buy a Digital AVO-Meter right now, for ... some reason, so i have to deal with what i have, and i'm willing to risk working on the card with the tools i have, no problem.
Thanks in advance guys, and sorry about the loooooong post :).
I'm an Aerospace Engineering student, but i'm a bit weak in Electronics, as we only study the basics, we mainly study Mechanics (Structure, which is Mechanical Statics, and Aerodynamics, which is ... Gas Dynamics :P)and Thermodynamics.
Anyway, i got the pot thingie, and i also have an Analog AVO-Meter that has a problem with the Resistance measurement part of it, but it works perfectly for measuring Volts and Amps, i made sure of that through a lot of testing, so i can't measure any resistances.
I connected the positive pole of a 12v 18Ah (lasts 1 hour if 18A are drawn from it, less if more are drawn) battery to the first outer leg of the pot. Then took the second outer leg and connected it to the negative pole of the battery, and then set the meter to measure DC voltage, and measured the potential difference across the first outer leg and the middle one What i noticed was that the the meter read 5v, and 7v across the second and middle, when i turn the screw, it decreases and increases depending on the direction, so the pot is working :P.
Now, like i said, the resistance measuring part of the meter is not working, or working but doesn't provide anything but an indicator if there's a short or open circuit, and it says 200k Ohm when at idle, even if i try to adjust the skew (forgot its exact name). So i measured the resistance across the 2 outer legs, result ... shorted (0 Ohm), turned the screw all the way to the other direction, result ... shorted (0 Ohm), adjusted the range, same result on all ranges, even on 1 Ohm or 1 MOhm accuracy, measured across the outer and middle, same result.
All that was on the multi-turn VR, i got another VR, but single turn, i tried to measure the resistance across the 2 outer legs on that one, and it didn't give me a 0 Ohm, but 'a' resistance, which doesn't change neither by adjusting the range, nor by turning the screw.
Now my question ...
why does the resistance get SO hot when i try the 3 legged connection which works well?
why is the first VR always shorted, and the second gives 'some' fixed resistance?
why is it working on 3 legged connection only?
also, how can i make a 3 legged connection for this card's (HD 3850 or 70) volt-mod please?
note: i can't buy a Digital AVO-Meter right now, for ... some reason, so i have to deal with what i have, and i'm willing to risk working on the card with the tools i have, no problem.
Thanks in advance guys, and sorry about the loooooong post :).