I would remove the PSU wires from the board (making sure that there is NO power going to the board in any way) and measure the resistance at the board where you removed the PSU wires. Make sure that the Positive lead from the ohmmeter is connected to the positive input on the board. It sounds as though something could be shorted out on the board, but you will need to determine that with the ohmmeter. Let me know.
ok, so just so i'm 100% clear, it was the wire going from +VE on the PSU to HB-PWR+ on the Rumba that freaked out and caught fire. there's 2 power input sections on the Rumba. One goes from +/- on the PSU to +/- on the 'MAIN-PWR' section of the board. The one I'm more concerned with is the ones going from a separate +/- on the PSU to +/- on the 'HB-PWR' section of the board. I measured the resistance from + to + and - to - between the 'HB-PWR' (where the PSU voltage comes in) to the 'HB-OUT' section (where the Heater for the bed is connected) and got the following: + to + = 0R - to - = 19K + to - = E (max resistance/no junction) - to + = E Also, I'm going for S16 guage wire, which is approximately 3 times heavier than the older one.
Finally getting a chance to work on this later. Quick question, if, when I disconnect the heater and check the resistance between the two wires, the resistance is still around 1R, then I should alleviate the problem with some heavier wire between the PSU and the HB-PWR terminals, right? Is there anything else that could be causing those wires to overheat?
If the wires are overheating then they are too small for the current passing through them. Double them up with the same size wire or replace them with with larger wire.
I thought as much. Resistance is still reading at 0.9R, so I'm swapping out all the wires from the PSU to the board. comparison of old wire to new wire:
uh oh.... So there's a faint smell of something burnt, the fans just shut off, and silence. There's still power going to the board, but the smell of burning is worrying...
Is it possible that the power supply is too small to output the power needed? The other possibility is something is drawing too much power or is shorted.
it's the same power supply that e3d stock from what we can tell. outputs 21A, so maybe I need to go back to looking at yet another heated bed with a bit less draw?
i think the fuse is now blown anyway, so I cant check anything else for a few days till i get a replacement one. Time to look at power resistors again maybe. :/
finally getting back to working on this. and, after frying a brand new power supply from e3d, I decided enough was enough... 700W ATX Supply putting out 58A Max on the +12V side of things. That should do it.
