Heated Bed not heating....

[mchawkeye]

So...old school M2, 12v machine.

Now I know that older machines, like mine, have an issue with the plugs from the power supply to the back of the Board. which I have had in the past, changed the plugs out. worked again. nice.

In fact, I had to do that again recently. (so as an aside, if there is any permanent solution to the bed not melting various plugs, that would be good...)

since then (about 2 weeks ago) I have been working my M2 rather hard on a professional model making project. So its been running most days. And its been brilliant.

until this morning, when the bed plate has decided to not work. I am getting a thermistor reading from it. I have checked the plugs at the back of the machine, the connectors at the plate are good. checked the power supply was all good, which it was.

I did look at the plug on the inside of the board (on the wires marked HBP) and that was melted, replaced it. still no joy.

I wouldn't mind, but like I say, I need this machine to be working right now, so its kinda urgent I get this resolved. Any help will be met with unadulterated happiness and joy.

[ednisley]

working my M2 rather hard

Which means a wire between the RAMBo and the platform heater has finally broken, most likely where it leaves the silicone heater pad and takes flight to that first connector:
https://softsolder.com/2013/04/07/maker ... orm-cable/



Unplug the connector and measure the resistance between the pins on the platform side, which should be no more than a few ohms. If it's open, you've found the problem, but more likely it'll be intermittent: as you wiggle & jiggle the wire, the broken strands will sometimes make contact. In either case, you need a new heater & plate, which may be the start of the long-avoided (and highly recommended) upgrade to 24 V power.

A less likely failure lies along the cable from that connector to the RAMBo board, so unplug both ends and measure the resistance of each wire separately while you wiggle & jiggle.

Good hunting …

[mchawkeye]

I did test that, and the results were intermittent, which makes me think the bed wiring is FUBAR.

now the issue here is being in Scotland, and not being a zillionaire, and getting spare parts delivered in time.

are there any "quick fixes" that I can do to work around the problem in the mean time?

[ednisley]

any "quick fixes"

Some folks have achieved (temporary) success by carving into the silicone pad, exposing the wires, cutting out the failed sections, then applying a generous dollop of solder. Given the crumbled strands, high current, and low conductivity of solder, that's probably not going to last long, but you have nothing to lose.

Other folks may have more optimistic suggestions … [grin]

Also: if it's for business, you need spares. Lots of spares!

[mchawkeye]

any "quick fixes"

Some folks have achieved (temporary) success by carving into the silicone pad, exposing the wires, cutting out the failed sections, then applying a generous dollop of solder. Given the crumbled strands, high current, and low conductivity of solder, that's probably not going to last long, but you have nothing to lose.

Other folks may have more optimistic suggestions … [grin]

Also: if it's for business, you need spares. Lots of spares!

I thought it might come to that! Time for some exploratory surgery...

As for spares, well, in an ideal world, you are not wrong. but those spares cost lots of money to buy, and no small amount to ship over here. and I am not in a position to do that, sadly.

Thanks very much for your help!

[mchawkeye]

the more I think about it (and some exploratory looking at the wiring from the bed showing no breaks...) the plug into the mosfet was melted. could the board be done?

[ednisley]

could the board be done?

Probably not, but replacing that charred connector will be daunting.

If you're up for a firmware recompilation adventure, you can swap the platform heater output to a different MOSFET heater (not fan!) channel and try again. Because the plug on the cable is probably wrecked, it won't make good contact with the new socket, cause an(other) early failure, and then you're really stuck.

You can control a husky DC-DC solid-state relay from the MOSFET to get the high current off the RAMBo and prevent more destruction:
https://softsolder.com/2013/10/11/maker ... hermistor/



Because the SSR doesn't draw much current from the MOSFET, you could solder small wires directly to the destroyed connector's PCB traces (under the board, perhaps) to avoid replacing the connector.

But it'll take just as long to get a DC-DC SSR as whatever repair parts you need from MakerGear, so maybe that's something to consider for later.