MKS GEN_L heater bed not working

I modified the electronics on my FLSUN I3 plus to incorporate a different power supply and added an external mosfet to the heater bed output. I also added a economy controller as well as the TFT touch screen.

This worked fine. However during a print today I had a thermal runway message. Now there seems no output from the MKS GEN_L board.

Is there a way to fix this? Do I need to buy a new board

I wondered if replacing the board Mosfet or if there were some kind of fuse that might be possible to reset/change. I guess the lowest (nearest to hot bed output) mosfet is the relevant one.

I am not clear what has gone wrong, here is what I find so far:

The bed with 12v applied directly gets warm."
The hotbed output from the gen board seems dead. Not even a LED on the board lights when I do a "PLA preheat bed" from the simple control panel.

I have not tested the external MOSFET yet.

Any ideas?

Any ideas?

Edited 1 time(s). Last edit at 11/29/2018 12:46PM by Tryit.

If the led is not on, its not trying to turn on

check the bed thermister is reading room temperature

Briillint!

Schoolboy error I was testing having removed the bed from the machine.

Wired it up and it appears to be to be working !?!?!

Figured it out!


Unfortunately prints were still failing with thermal runaway errors.

After many false trails I found the external MOSFET board was working intermittently. Once I got to looking at the rear of the board I found one of the terminals had a dry solder joint. It now works! Discovered after having ordered replacement - oh well!

Quote
Tryit
After many false trails I found the external MOSFET board was working intermittently. Once I got to looking at the rear of the board I found one of the terminals had a dry solder joint. It now works! Discovered after having ordered replacement - oh well!

Learned something new.
Can not remember every hearing of a dry solder joint, we always called them cold solder joints. AKA Broken solder joint:

Lookup on Web for Dry Solder joint. A cracked, fractured or broken solder joint is sometimes called a 'cold' or ‘dry’ solder joint looks dull and crusty.
You might even see a ring or crack around the pin or leg.

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Computer Programmer / Electronics Technician