Why i hate cheap molex connectors.
Anyone who has ever built a mining rigs knows what the second best thing they do next to mining is. They heat up the room like no other, and that heat needs to be moved as far as possible away from the mining rig itself.
Since my two mainboards only supported four case fan's in total i needed to look for another solution to get my fans powered. After a little googling i found this delock 6x fan power splitter. The designers must have had a giggle handing the new product over to the marketing department, as i noticed by my own smile due to the product number (FAP-PDB2 ). So for building my rig i needed a FAP, and ordered one which was done within a minute. Completely satisfied i waited for the part to arrive.
Unboxing.
With a double degree in electronics and software development, i'm always interested in how a product is built. And i wasn't really dissatisfied with the things i saw. So as a true "expert" i unplugged the fans from the mainboard while the system was running and mining, and turned on all six fans that started humming away. 6x 120 mm of air movers where trying to keep my cards below 70 Celsius. They managed to do it quite well, except for one card that seemed to be placed in the exact middle of two fans. I had another 120mm fan somewhere in my pile of electronics, but it was missing the connector. So as a test i used my bench supply to power it, and the strange thing was that it was moving a lot more air than the others. I unplugged one of the fans, and moved it over to one of the mainboards (ofcourse with the system powered on !) and the RPMS didn't increase.
Solving the puzzle
So i went into my bios, and saw that it had a temperature profile for the fans, but since we were not running it in a case, the thermometers would say the system was cold. Since i hate heat, and even stay out of the kitchen for that reason i set the fans to max and exited the bios. So now i had 4 out of 6 running at max speed, but the ones on the distributor where still dodgy, but i just left it for that. A couple of days later i was cleaning up a pile of obsolete computer stuff and among it was a Seagate ST-251 (lookup how it sounds on YouTube) and i remembered frying one of those because of a cheap molex that allowed me to put in the connector in the wrong way. Now for a hard drive, you switch five and twelve volts so you fry the five volt circuits, but in the case of a 12 volt fan, you only supply it with five volts. After inspection i saw that i made the same mistake again of trusting "if it fits, it sits" and i was choking my fans at 5v. After pluging in all fans in the Fan Power - Power Distributor Board 2 also know as the FAP-PDB2 and reversing the molex everything was working fine.
Lessons learned
- A degree says nothing, you can still make beginner mistakes.
- Power off, and check cables before powering on again.
- Be extra careful with soft plastic molex connectors.
- 6 fans isn't enough for nine cards.
- Even with a mining bios on the mainboard, not everything is set to mining optimums by default.
- My BeQuiet pure wings 2 are at full rpm very silent compared to the other 120mm i removed form the pile. Even six of them are more quiet than the single generic chinese branded one.
Keep Hashing !