So I supplied a 48VDC passive POE signal into a cheap $5 Ethernet cable tester… As there was no protection circuitry in the tester, the LEDs for pins 4 and 5 blew (Mode B PoE supplies power between 4-5 and 7-8).

The timing was quite unfortunate, because the next day I would need to make some cables for a friend. I purchased a replacement one but I needed it tomorrow, and waiting any faster won’t help (Fun fact: It never arrived… EDIT: It arrived after about 9 months of waiting!).

So, I guess it’s time to fix it!

Opening up the case and looking at the circuit board, there was a bit of copper swelling on traces for L4 and L5, probably as a result of the voltage spark.

As LEDs 4 and 5 had blown, it had left an open circuit for pin 4 and 5 - hence why I could not see the continuity on the signal transmitter.
My solution to get things working was to short the traces for pins 4 and 5, bypassing the (broken) LEDs.

Now they say that a good workman never blames his tools.
Sure, but that’s only if your tools are DECENT.

Man, my soldering iron sucks - It gets hot way too fast, and the tip of the iron doesn’t even get hot, I have to heat up the solder from the sides

Or maybe I’m just not a good workman???

Anyhow, because of my poor quality soldering iron / poor quality soldering skills, I ended up breaking the copper pads from the SMD LEDs.
Consequently, I had to expose the copper tracks with a pocket knife to get a new connection point, which I was then able to bridge to the return track.

After soldering the tracks for pins 4 and 5; I managed to shove the circuit board back into the case, and thankfully it worked!

(Note: If you own this model, you won’t see all of the LEDs light up at the same time - I took a long exposure photograph, to prove that all of the LEDs light up)

Update: 30th July 2020

I ended up buying a Nofaya NF-488 digital cable tester; as I’ve been meaning to purchase a digital tester for a while.

It shows you if pins are mismatched, isn’t that cool!

That being said, I also purchased a PoE detector - In case the NF-488 didn’t support Passive PoE, as I didn’t want to bust yet another tool.

But it looks like it does (thankfully!)