... it seems pretty weird for that to of gotten so hot to char the insulation and the plugs on both ends.
A good power supply makes a big difference - how are you powering the boards?
That miner is being powered with a set of the HP server psu's and I have had a few problems with the power plugs on that particular board on that miner and no matter what power supply i had on it they would get ripping hot right at the plugs going in to the board. and even changing the plugs on the power supply they would still get so ripping hot they eventually melt them selves in place and the last time it happened I had to bust off the plug charged connectors on the board and replace them and clean up all the pins so I could finally get a good resistance free connection without them getting hot when running for awhile. Tho I did happen to notice a tiny bit of a brownish burn on the ribbon cable the last time I had a problem with the power plugs. BUT I had assumed it was just because it was so close to one of the burn plugs that I thought it was just from that and didnt really think about the ribbon cable too much more till today when it was all burned up and melted..
So it does seem related to the burning plug issue. BUT now im wondering if instead of it being the power plugs causing a prob with the ribbon cable as well. Im starting to wonder it might of been the other way around and something not right with the ribbon cable from the start causing problems with the power plugs. Because now with the new ribbon cable in place them power plugs on the board are not even getting all that warm now at the power connectors.
I just ended up figuring out that I can borrow a replacement off of my s7 and got the s9 going again while I wait for a replacement and it seems to be working and the wire is so far staying cool. But I'm going to watch it like a hawk all day.
We use those PSUs as well...good bricks, btw...but had a severe issue some time ago with a bad batch of pigtails. They weren't mated to the plug end properly; the connections to the board would char and melt.
It wasn't the miner, or the psu...it was the cable itself. We switched supplier on the cables and haven't had a problem since.
Orginaly when I started haveing problems with the plug ends it just so happened to be just one set of wires that were from one supplier. Who also happened to have some breakout boards that are not all that great either compare to some others. But I ditched the breakout boards and now just solder my pig tails directly on to the blades on the backs of the psus. But the plug ends were still really crappy. Most of the crimped pins were not even crimped on to the wire all that good and haveing to mess around with them and unplugging them is not good for them either.
I Now have all the crappy pig tails and plugs ends all replaced with all new wires- 6 per plug instead of just 2 per plug, New plug ends as well as made sure I got the right female pin connectors that are platted and meant for higher amps. And the seem to be staying pretty cool all the way from psu right up to the plugs now.
NotFuzzyWarm I would tend to think that the negative 12v trying to find ground there the ribbon cable would def explain that cable even getting burnt in the first place and on both ends no less as well. I could not see how 3.3volt data could of done it. BUT 12v and high amp back feeding through makes a lot more scence. I'm thinking the damage to the ribbon took place when it first got charred from the power plug problem which was just the other day and replacing all the power cables to that blade. But thinking the ribben cable could wait to be replaced might of still left me with the cable already being ruined or just one touch or movement away from compleat failure.