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jemma-redmond

um1 main board blown again!! any ideas how to fix?

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Hi,

I've been having lots of fun with um1's constantly repairing them. However the latest one is the mainboard, the power went (for no reason). The lights won't come on, the power supply is fine (tested on another machine) power cables tested, mega 2950 tests fine.

So while I would love to spend another 250 euros on electronics that keep blowing up, I was just wondering if anyone had been able to successfully repair the mainboard and if so how did they do it? I have about 3 damaged boards so far... (don't ask, ((groans and puts hands on face))

:-P

 

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well, not sure how a pic would help... there are no burnt components, no corrosion, no breaks in the circuit, voltages shows 19V going in, less than 1v coming out on the 19V fan output beside the L7812VC transistor or regualtor? at the back... there is no voltage across the regulator, there is a 4.7k resistor soldered in for a heated bed, the sensor was wired in but not for power etc so I don't think this has anything to do with the problem...

IMG 0572

 

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It would make sense to suspect the 12V regulator (LM7812), because if that one is dead, then the machine doesn't run. The LM7812 is used to power the arduino (and pretty much everything else is powered by the Arduino board, except the stepper motors and heaters).

Note that if the LM7812 is dead, then there is some probability that this was caused by a faulty Arduino board (which is the only thing that is directly connected to the LM7812).

But you say you have checked the Arduino. How did you power it? Have you unplugged it from the shield and connected the 19V UM power supply directly to the arduino? (Note that you should not do that while the Arduino is connected to the shield and the rest of the printer).

The Arduino can be powered from 20V, but in that case you shouldn't draw a lot of power (like connecting any peripherals such as the Ulticontroller) or the Arduino's linear regulator will get very hot.

 

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Ok, soooooooooooo I had a dodgy board 1.5.7, the 19v led lights up but the regulator overheats and the voltages are weird so i figured it was faulty, so as that was all i had i cut that one out and resoldered it onto the board in the picture. The result? The 19V light went on. but the regulator was still misbehaving, plugging in a known to be working mega still resulted in the 5V led line not lighting up, and the uni controller display not powering up.

So I'm pretty sure at this stage its the regulator... I swapped the mega into a working machine (my diybio/bfb3000/ultimaker hybrid) and it worked fine. So thats ok. I can only assume there was power surge somewhere while I was working on the machine. However this is supposedly a state of the art lab in a biomedical facility so surely this cannot happen? ha! probably not. So I've put all of the machines onto surge protection sockets just to be safe.

I'll be in the city later so I'll pick up a regulator from maplins and do the repair tomorrow, if it works, horray! if not, boo!

 

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I recommend unplugging everything from the UM shield (except the working Arduino) and try the repaired shield like that.

Then re-connect all the peripherals one by one (always power-off before connecting anything, of course!). There could be a short-circuit somewhere which blows the regulator.

Theoretically, it should enter thermal-shutdown (over-current protection) instead of blowing. That is supposed to work...

 

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I don't know but the white connector for the electronics fan on top of the picture looks rather burned to me. So it might be the voltage regulator beneath it...

 

That is what I thought as well..

Isn't that part converting the 19V into 5V?

So if it broke it is letting all the 19V go through?

(electronics are not my field of expertise.. even after all these years.. :oops: )

 

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It converts 19V to 12V and then the arduino takes the 12V and converts it to 5V on the arduino.

That part is supposed to be bent up into the air flow (it doesn't look bent up enough) according to the directions. That regulator is easy to blow up if for example the fan stops working/spinning. It gets very hot. To make it more "bullet proof" you could replace with a switching regulator part - costs probably 0.60 pounds instead of 0.30 pounds. Something like that. You want a regulator that takes in 19V, puts out 12V but I'm not sure of the current load.

Also some people have screwed on heat sinks to that part so that it stays a little cooler.

You can also destroy it if you short the 12V to ground for an instant while poking around with power on.

 

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H!

So I replaced the reg on the board and hooray it worked! It cost like 1.50 euros from maplin. However with the other blown board I replace the reg and the 19V led lit up but when I plugged in the mega, nothing, no power to the mega and thus no power to the display. Soooo what other components usually go on the mainboard apart from the regulator? I have another faulty board and I was thinking of swapping parts from there. But I'd like to narrow down the possibilities... any advice?

Ta

Jem

 

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It's a little dangerous to take parts off a blown board as one of those parts might be the "bad" part.

check that the regulator has 19V, gnd, 12V on the 3 pins. If a freshly replaced part still has < 1V on the 12V side then feel the parts - one of them is probably getting very hot. That's the bad part that is causing a short. Meanwhile your regulator might blow up again. So don't wait too long.

If however you have 12V just fine then the arduino should power up. If not then the arduino is probably bad or the 12V isn't reaching the arduino (it doesn't have to go very far!).

 

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It's a little dangerous to take parts off a blown board as one of those parts might be the "bad" part.

...

 

Additionally, you shouldn't plug / unplug the arduino from the shield too many times as these connectors are simply not made with lots of "mating cycles" in mind.

I actually tore some of the headers apart the second time I unplugged my Arduino...

While you might not completely wreck the connectors, the electrical resistance may rise (due to bent contacts) and lead to other problems.

The most basic IT rule of all applies:

Never touch a running system ;)

/edit:

That only accounts for the electronics part! The mechanical part will need some occasional lubrication and re-tuning...

 

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What do you mean by "causes the machine to shut down."?

Are the LEDs still on? Ulticontroller? Anything working? Does it "hang"? Display an error? Is the USB comm still occurring?

Are you saying you can take the temp sensor cable with nothing attached, plug it into temp2 without problems but you take the exact same cable with nothing connected and plug it into temp1 and things stop working?

 

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It's probably one of the heater circuits. With nothing in temp1 it probably doesn't turn on the heater circuit. Turning it on probably causes a short - the FET that turns on the nozzle heater is probably blown. If you don't need heat you can just cut that 3 lead part out completely and toss it.

 

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well ok, you probably won't believe this but its working again... I disconnected everything and pretended I was playing buckaroo (you know where you put the mining gear on the donkey and it kicks it off if there is too much) so I plugged all the wires in one at a time and then it bloody well worked!.. I've setup two extruders and what I did find was a dodgy wire coming from one that was causing the machine to switch off.. Now hopefully that IS the problem this time but who the hell knows?

Perhaps today it will explode in a fireball? :-P

 

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