crush depth

Pennies Saved On Construction

In a previous episode, I moved the contents of a server into a new SC-316 case.

While the case seems to be of generally good quality, mine has turned out to have a serious fault. The case's drive bays are implemented in terms of four mounted PCB backplanes, each with its own power connector and SAS connector. Each backplane is individually powered via a standard completely awful AMP Mate-n-Lok 1-480424-0 Power connector.

Anyone who's dealt with these connectors knows how bad they are. They're next to impossible to plug in, and next to impossible to unplug once plugged in. To quote that Wikipedia page:

Despite its widespread adoption, the connector does have problems. It is difficult to remove because it is held in place by friction instead of a latch, and some poorly constructed connectors may have one or more pins detach from the connector during mating or de-mating. There is also a tendency for the loosely inserted pins on the male connector to skew out of alignment. The female sockets can spread, making the connection imperfect and subject to arcing. Standard practice is to check for any sign of blackening or browning on the white plastic shell, which would indicate the need to replace the arcing connector. In extreme cases the whole connector can melt due to the heat from arcing.

To summarize:

  • The connector is difficult to plug in due to a friction fit.
  • The connector is difficult to unplug due to a friction fit.
  • The pins can be bent and damaged should the user do something as completely unforgivable as to plug in the connector.
  • The pins of the connector are subject to arcing, risking a fire.

And yet, somehow, we're fitting this ridiculous 1960s relic onto modern power supplies, despite far better connectors being available such as, frankly, any of the 15A and above rated JST connectors.

Back to the story. I connected the power supply to the top two backplanes, leaving the bottom two unpowered. I didn't have SAS connections for those backplanes anyway, I really only needed a 3U case because it was going to need to contain a full-height PCI card, and there wasn't a reasonably priced 3U case that didn't also come with 16 drive bays.

I placed some disks in the second row of bays. The lights came on, the disks were accessible, no issues.

I placed a disk in the top row of bays... Nothing. I tried a disk in a different bay on the same row... Nothing.

I shut the machine down, dragged the machine out of the rack, opened it, and took a look at the backplanes. Nothing appeared to be wrong until I wiggled the power connector for the top backplane to check that it was correctly plugged in.

Uh oh.

The entire power connector came off in my hand.


It turns out that the power connectors are not through-hole soldered connectors. They're rather flimsy plastic connectors that are screwed onto the board. You can see from the image that there are two thin plastic ears on the connector, and the ears have simply ripped off. Real AMP Mate-n-Lok connectors are typically made from nylon - these connectors do not feel like nylon, and I don't think nylon would have torn this easily.

I inspected the rest of the connectors and discovered that the bottom connector (that I'd not even touched) was also cracked on one side:


This effectively leaves only two of four sets of drive bays functional.

I'm waiting to hear back from ServerCase support. This will be the third time I've had to use their support, and they have been excellent every time, but I'm not looking forward to the possibility of having to take everything out of the case and sending the case back.

My ideal outcome for this is that they send me new backplanes with real connectors on them, properly soldered onto the board. I realize that's unlikely. I've already been looking at replacement connectors that I can solder onto the boards myself. There are some connectors from TE Connectivity that look like they would fit.