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So after a year of no issues I have finally had a possibly very expensive mishap. As I was preheating my heated bed (PN 58742 R2) I started to smell a very unsettling burning smell coming from my printer. I opened up the front to inspect the RAMBo for the cause and found the root of the problem as shown in the following picture:
The only damage I can see so far is the fried connector and the heated bed is possibly dead. Also the 15A Blade Fuse did blow and the capacitor next to the burned connector appears to be just coated in smoke residue and nothing more. The rest of the RAMBo as far as I can tell still works; all the leds light up, the two other fuses are fine, and all the components and connectors still work.

I would rather not spend a whole lot on unnecessary components so I am wondering If I would be able to just replace the burned connector and not risk any further damage to the printer. I plan on sending the board out to Ultimachine or SeeMeCNC to test the board and assess the damage but would like an opinion on what everyone thinks beforehand so I can plan and order parts accordinly.

Some have even cut those two terminals off of the rest of the block and either replaced them with a two-terminal screw terminal or soldered the wires directly to the board.

It's not hard to find the right part spec (Ultimachine has open source documentation for the Rambo, which I believe includes a BOM). Harder would be removing just the crisped two connectors (Unless you want to replace the whole strip) without damaging the board (Someone used a dremel). Considering the history of similar issues, it's likely just the connector and possibly the capacitor which are damaged. Have you done much if any soldering?

If so, you can pull it okay with an iron and desoldering tools, and pull the cap too to check for degradation (while it may not be outwardly damaged, it may have been harmed by the nearby temps if it's a low operating temp capacitor)

Here's a previous thread about this issue, which in turn points at other previous threads: http://forum.seemecnc.com/viewtopic.php?f=37&t=9892

Yes, it's something you can fix yourself, if you have the skills to remove the bad and solder in a replacement.

But if you plan to send it to Ultimachine anyway, you may find it easiest to have them fix it for you.

Ok, so I just finished soldering on two terminal connectors in place of the single terminal block.
This should hopefully make it easier to replace only certain terminals instead of the whole block. Now I just have to get a 15A blade fuse, and have this available locally: http://www.allelectronics.com/make-a-st ... use/1.html. Would this be the right fuse to get as a replacement?

You should have the fuses at every gasoline station.

That's your standard automotive blade fuse. Auto parts stores (e.g. Napa) or places with an auto parts section (e.g. Walmart) will have them.

The nano fuses are another matter....they're pretty much order-only items, unless you happen to live near a real electronics parts store.

I stopped by All Electronics and bought a couple of fuses. I will reconnect everything when I have the time and hopefully shouldn't run into any problems, but will post back if I do. Thanks, for all the help!

Good job in fixing your board!

Ok, So after wiring everything back up the heated bed is now heating however there is a new issue. The heated bed seems to turn on as soon as I turn the printer on. The bed starts heating and the RAMBo LED for the heated bed is on. I think the problem is caused by the capacitor next to the heated bed terminal as it is warm to the touch when the printer is on. The thing I am not sure about is whether or not this is a result of the previous damage to the heated bed terminal or something else. I am going to buy a replacement capacitor to replace the faulty one I but am wondering if this is the best way to go about testing this problem or if there is a better method to diagnose the issue.

Oh dear. You may have busted your mossfett.

teoman wrote:Oh dear. You may have busted your mossfett.

Yes! The mosfet directly under the terminal is burning up. Is it worth soldering on a replacement mosfet or is this board most likely toast?

The decoupling capacitor is unlikely to be the cause of your current problem, although replacing it certainly won't hurt anything. It's probably warm because it's connected to the power and ground planes that the mosfet is using as a heat dump.

The mosfet does sound like the most likely candidate. If it were me, I'd take a gander at the schematics (find them at http://reprap.org/wiki/Rambo) and test to see that the input to the mosfet actually disagreed with the output state with my trusty meter. Or you can just go ahead and replace it. The part number will be on that schematic. It's cheap enough, but if you can't find it locally shipping will probably quadruple the price.

Sending the board back to Ultimachine for them to repair is starting to look better and better.

How much would they even charge for a repair anyway?
If you want I could sell you my rambo - I recently upgraded to a duet so my rambo is just sitting around gathering dust atm.

bob64 wrote:How much would they even charge for a repair anyway?
If you want I could sell you my rambo - I recently upgraded to a duet so my rambo is just sitting around gathering dust atm.

I do not know what they charge for repair, can someone who has sent one in for repair advise us of the approximate cost?

Success! I bought a replacement mosfet and soldered it on today. The printer seems to be working just fine and I am currently preparing to print some test prints! Thanks for everyone's help.

Great news! Glad your soldering skills were up to the task.