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January 27, 2014, 10:45:41 AM |
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My guess is the fan,
witch is a part of a safety circuit so the cube wont overheat.
I think this circuit measure the inner resistanse of the fan comparing it to the 12v rail. when its a mismatch the safety circuit cut the power to the relay and its shut itself off.
When you hit the overclock, the 12 v voltage is dropping (maybe some mV), the circuit is measuring the 12v regarding to the fan current (which is the voltage indirectly and therefor the innerresistance, conf ohm's law, U=R*I). If its a mismatch it turn itself off.
it seems to me that the electrical tolerence of the fan and the safety circuit is very sensitive. Sometimes when i touch the cube i can hear the relay is clicking.
You can test this just to disconnect the fan when the cube is running or partly block the inlet/outlet of the fan so it changes its rpm, and the circuit will switch the cube off. Of you can try with another fan with the same electrical caracteristic. that will maybe solve the problem.
i believe the tolerance for the "fan-part" of this circuit is very small, maybe within a few mA.
A really dirty solution is to bridge the contact point on the relay. But you will then not have a safety circuit in case of overheating!!!
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