Hotend not heating up  

Hotend not heating up

So, this is going to be a long one.

Got my mk2s last year, and it has been working stable until Chrismas.
First problem was that the connection plug from the rambo to the heatbed started melting, and the hotbed stopped working.
Got my local electrician to solder wires directly to the rambo, to remove this specific source of problems.
After setting the printer back up, the heatbed worked as it should, but the hotend didn't heat up at all.

I took this to the online chat with Prusa, and checked a lot of potential issues
- 2 different hotends to remove the possibility of it being the hotend itself that was the problem,
- Thermistor working (heatgun to see that the temperature was rising)
- Power input stable on both rails
- Changed all the fuses (just in case)
- etc...

After checking that there wasn't anything wrong with all this, I got a new rambo in the mail.
First thing I did was to get my electrcian to solder new connections to the rambo, to avoid another meltdown of the heatbed connector.

Then I carefully connected everything, and got the exact same problem as before, the hotend is not heating up.
I got my multimeter out, and checked that I get 0 volts on the hot end connection at the board when I try preheating.

Since I had a 2.5-upgrade on order, I set the printer aside until I got this, hoping that the upgraded bed would solve the problem.

After upgrading to the 2.5, I have the exact same problem.
The wizard goes through the fans, and then stops with the error "heater/Thermistor not connected".
When I check the rambo, there is 0 volt on the output to the hotend, but the led lights up and everything seems fine.
I have gone through the same tests again, power input is fine, thermistor working, fuses are good, and checked with 2 different heaters.

I suspect that I got a shot circuit on the original mk42 heatbed that somehow fried the rambo, and when I reconnected everything it did the same to the new board.

So, what would you suggest?
I guess buying a new rambo might be a way to go, don't exactly think that support is going to send me yet another one.
Spending another 150$ is not what my wife wants me to do at the moment, so I need to hear if you have any suggestions first.

Regards,
Ove