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September 25, 2014, 07:17:30 PM |
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The fans give a speed indication output. I don't know what kind, digital or analog. The fan speed is controlled by pulse width modulation. I don't see a corresponding hashing board temperature and fan speed though one goes up so does the other. If I saw three miners having a 40° board temperature and all three have the same speed, I'd say there was a digital feedback loop but this is not the case. So, one might assume that there is a ramp or curve that says when the temperature is A the fan speed supply voltage will be X, temp B gets voltage Y and temp C gets voltage Z. The speed indication just giving an indication of change versus temperature to the user.
The bad hashing board having a declining hashrate and a declining temperature might indicate the fault is elsewhere except that even after a cold start, after significant cooling time such that hashing starts over 442 and works its way down over hours, shows a lower temperature and fan speed early on. If that slower fan speed causes errors away from the temperature sensor, those ASICs may shut down engines and slow hashrate but not quickly effect temperature indication.
So the slow fan speed relative to temperature should be addressed. The problem may be in the pulsed width voltage supply line. A partial open, high resistance, in a plated thru hole, e.g. dull drill bit left fiber in the hole, the hole only partly plated. So, that's where I'll look first when I troubleshoot. I'll follow the pulsed with fan voltage first, then the ground and perhaps the speed indication pair, looking for something amiss. But not today.
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