WS-6-Mini died, trying to determine why

[JayDee]

Here's the setup:

We've got a WS-6-Mini powering a MikroTik CCR-1009 (48V), and a MikroTik FTC11 (48V).

Powering the Mini (via its DC barrel jack) is an Iota DLS-5413 power supply. There is also a chain (series) of 4 12V AGM batteries connected to the same power supply output, in parallel with the Mini.

It was working fine for a few months, but had an issue where the ethernets would not negotiate a 1Gbps link. Only 100Mbps.

While trying to fix it, I power-cycled the Mini. It began booting, and at the moment when it decided to apply power to the connected loads (about 30 seconds into the boot process) I heard a "crack" sound, then a sizzle, and some smoke rolled out of the Mini.

It still came up and powered the loads, but it complained about being unable to measure output voltage/current, saying "Error". After I cycled it again, it would no longer power the connected loads.

With no other changes, I replaced it with another WS-6-Mini. This Mini works fine, and negotiates 1Gbps ethernet links.

So I'm left trying to figure out why it failed. The Mini datasheet specifies a maximum input voltage of 53V. The Iota power supply datasheet says it puts out 54.4V, with a 0.5% margin of error.

I wonder: Is it likely that too much input voltage killed it, or is something else afoot here?

Looking at the board on the failed unit, on its underside the 5-pin "U43" component appears to be the source of the escaped magic smoke. Nothing else looks visibly damaged. The board says "Rev B".

[sirhc]

I asked Dave to review this post and chime in but the MINI is designed to get conditioned power and is not designed to accept more than 53V
We are working on a small product similar to this which will accept 9-60V like the WS-12-250-DC but this device is not.

Also curious if your tower grounding system is bonded to the equipment ground/service ground? The reason I ask this is if not the current sensors can get damaged.

These are 2 good post to read and I recently updated them with more info:
viewtopic.php?f=30&t=188
viewtopic.php?f=30&t=1429

[Dave]

More than likely your power source put out more than 60 volts, maybe even for a short duration, or you have a tower ground issue, causing a possible ground shift (could be caused by poor grounding system and or bad weather (storm water around grounding rods). The part that you said went on to its after life, is rated to 60 volts, so it had more than 60 volts applied to it, either in the form of the actual 60 volts going above 60 volts, or a combination of a high supply voltage & a ground difference potential.

Personally, I would not use more than a 50 volt power source, and I would double check your towers grounding system.

Dave

[JayDee]

Hmm.

I'll have to check out the tower grounding situation and take some measurements. I can definitely see the potential (no pun intended) for current to flow through our equipment in unexpected ways if there were a significant voltage difference between the tower body and the electric service ground. It wouldn't be the first tower site I've seen like that.

These power supplies are convenient to use because they're designed to charge and maintain a 48V series of lead-acid batteries. It ought not to have put out 60V+, but I guess it's possible. I'll try and take some measurements of that also.