Basically there are 3 levels of surge protection:
- Direct lightning strike, Type 1.
These things are fucking huge, think 19" cage filled with biggass MOV's and spark gaps.

- Normal building ones, Type 2.
These you mount in your fusebox and protect the feed it is on from high overvoltages, but not direct strikes.
They are the size of a large current breaker.

- Plug-pack of socket strip type ones, Type 3.
The only protect the device directly connected to it.
These you also have for phone line, ethernet, etc.

In some countries having type 2 is mandatory, I have one here because I can, my electrician didn't know they existed (sigh).

Type 3 isn't very useful without a type 2 nearby, they can't protect against a lot of power (since they are small).

Keep in mind they they need a really good ground connection to be effective, if they can't short high power to ground they won't do a thing.

Besides the types you have ones that protect phase/neutral separately to ground and types that protect them to each other and then to ground.
The difference between them is not that huge, the second type usually has a lot lower activation voltage on neutral, but most devices can have mains voltage on the neutral without problems so that doesn't really matter.
The type 3 ones are always the first type, simply because you can't count on the neutral being on the correct pin, type 2 ones are mostly the latter.

That is good to know.

The two boards that give 30 asics I just didn't count them and assumed the count in the web interface was correct.
But indeed they have more asic's.

I'm currently focussing on the 2 54 asic boards that i have here (the others are still in my farm), what is see in the interface is this:


It has only been running 3 minutes here, but also at 30 minutes it doesn't display any x's.

In case it helps, I have run dmesg via ssh, it is filled with lines like:
http://bitcoin.sa007.nl/dmesg

If I run the same controller with a working 54 asic board, that one stops giving those lines after about a minute and starts mining, the broken board don't seem to start or something.

I still don't have a clue what is happening here.

I have 6 antminer S7's and some have a very low hashing rate, only one of 3 boards is hashing.

The strange thing is that I can't find anything wrong, the boards are detected, they have a normal temperature, no x's in the asic's but no hashing at all.
I did a firmware upgrade (even though they are at the newest firmware) but that did not help.

I don't know which batch they are (second hand).
I have 4 board with the same problem:
2 boards with 30 asic's
2 boards with 54 asic's (one shows temperature as 0).

Connecting them on different controllers or power supplies or lowering the frequency doesn't seem to help.
The 30-asic boards have electrolytic capacitors, they are fine (ESR and capacitance is normal)

I have a fully kitted out electronics lab if that helps.