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shurik

UM2 is dead after short circuit.

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Hey there,

Well, the age comes with its problems, as usual. It was quite a while since that red wire got loose, causing the fans to go off irregularly during printing, so I tried to push it back where it belongs.

But the device was not turned off, and a tiny hair of the red wire probably touched exposed part of its black neighbour... A small spark, and the printed went silent, and remains so ever since.

5a3327b8b88ec_shortcircuit.thumb.jpg.1c8b058e0216aec482d8758307bf1a39.jpg

Do I have to replace the main board or there is something else to check? Life is harsh...

5a3327b8b88ec_shortcircuit.thumb.jpg.1c8b058e0216aec482d8758307bf1a39.jpg

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Maybe the fans are still on short circuit? Unplug the fan on the board and try to turn on?

The PSU has a lot of safewards to protect himself, but maybe the transistor of the fan died. I would try connecting one by one, for example just psu without fans, if works, remove the fans. If doesn't... remove more stufff, if doesn't, remove the board...

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So, the printer is just completely dead? No display life or anything?

Are you certain the PSU comes online? And do you by any chance have access to a multimeter for measuring stuff? If the cause of this was indeed the model fans getting shorted, you've shorted VCC/2 (the unswitched 24V) directly (that is, you shorted it through the main board). And it shouldn't really happen unless the transistor is on. In any case, if I were you the first thing I'd do is make sure the power supply actually delivers 24V. The second would be to remove the main board and inspect it for burn damage.

Edited by Guest

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So, the printer is just completely dead? No display life or anything?

Yup.

 

Are you certain the PSU comes online?

Yup. The blue light goes on on the Power Supply, but the printer stays cold dead.

@onkelgeorg - the link is invalid, but you have a good idea - will look on the ifixit site later on.

 

Could be a transistor

I want it to be the case. The whole board is just so expensive.

Will disassemble it later in the evening to inspect it visually.

Thanks guys for your help!

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It sounds odd. But yeah, have a look at the board and see if there's anything to be seen - that certainly never hurt anything.

I'm not sure what the light on the power supply actually indicates. Power in? Power out? Assumption can mess up a great many things. Maybe someone else knows?

I'm not seeing how the fan transistor could conceivably cause the entire printer to be dead. Especially since you tried disconnecting the fan. If it was shorted collector-emitter, well, all that would happen was that we grounded a floating point. It would have to be a hard short of the transistor AND the kickback diode. The odds don't really seem to favour that. Something else must be going on.

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Well, here is the board. I do not see anything special, but I do not understand much in electricity anyways.

5a3327c094c85_MainBoard.thumb.jpg.3ddf9c0522613491e4b422575059db3e.jpg

@SyntaxTerror - this 3+ years old machine always, from the day 1 gave a small but tangible electricity shock when it was touched by anyone. So maybe, it wasn't that 100% good from the beginning. Dunno.

I have a multimeter device, but what should be checked? Or, maybe, there is a fuse that needs to be replaced?

5a3327c094c85_MainBoard.thumb.jpg.3ddf9c0522613491e4b422575059db3e.jpg

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Why the fan isn't plug on the 5V fan connection!??

So the short circuit did pass through the board without any resistor... Did you try to turn t on without the small hotend fan plugged from the board. Maybe you inly did unplug on the hotend and not on the board?

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From the schematics, the fan goes directly to VCC/2 (that is the 19v input). No fuse, nothing, just straight connection on the + side.

The ground side goes through the transistor.

So a short will definitely kill the transistor, and if it is dead we don't know for sure what it does... Typically it acts as an "All or Nothing" switch, but it can be anything else...

I find my way in digital signals, but I am not good enough in electronics to give advice as it could make the problem worse, but I'm afraid the short pushed current to the microcontroller and that is not a good sign...

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Hello,

What is the small connector plugged into J22? The Teflon insulator fan?

When you say the printer was not turned off -> 3 fans were running? Or just the small Teflon insulator fan?

Your problem looks like a short circuit on the 5volts that would roast the integrated circuit U6 (for pcb version 2.1.1 like yours)

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Why the fan isn't plug on the 5V fan connection!??

 

Perhaps because the connector pins are swapped at the plug? If you compare it with the documentation: black is now at the +5V side, and red is ground...?

 

Oh 3 years old... But that means that the short circuit could have damaged any part of the board right?

Edit: I see @electromu reply now...

Edited by Guest

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Why the fan isn't plug on the 5V fan connection!??

 

Perhaps because the connector pins are swapped at the plug? If you compare it with the documentation: black is now at the +5V side, and red is ground...?

 

Oh 3 years old... But that means that the short circuit could have damaged any part of the board right?

Edit: I see @electromu reply now...

 

I think you guys lost me now. I'm seeing a black wire on pin 1 and a red wire on pin 2 of J22. The 2.1.1 main board schematics want that to be the other way around? Is the extender cable pins swapped, you mean?

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I agree with electromu, it's most likely the 5V power regulator that is blown. Not the easiest part to replace sadly.

On the whole fan confusion. On older machines, there was no official connection for the small print head fan. This fan was added later in the design when the first large batch of boards was already ordered. (Those where chaotic times)

To get the 5V fan to work, we hooked it up to the 4 pin connector that you see now, this 4 pins has serial and power. (Actually designed to be hooked up to an Pi). Later a connector was added for this on the board, but due to variations in connectors this isn't used in this case. Most likely this board was already replaced once? As the connector on the fan cable is bigger then the connector on the board, requiring the old hackjob.

The fan could be power<->ground reversed, but that's fine, almost all fans do not care about this. And thus it's a mistake easily made by assembly.

Also note that there are 3 fan connectors on the board:

* Next to the 4 pins connect, this is 24V, always on.

* Near the limit switches, this is 24V, on/off by the controller, used for print cooling

* At the middle of the board, 5V, can be switched on/off in later revisions of the board. Missing in early versions.

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I agree with electromu, it's most likely the 5V power regulator that is blown. Not the easiest part to replace sadly.

 

It's not at all unlikely. I'd still start off verifying that the buck converter actually has 24V input before firing up the hot air rework station though.

 

On the whole fan confusion. On older machines, there was no official connection for the small print head fan. This fan was added later in the design when the first large batch of boards was already ordered. (Those where chaotic times)

To get the 5V fan to work, we hooked it up to the 4 pin connector that you see now, this 4 pins has serial and power. (Actually designed to be hooked up to an Pi). Later a connector was added for this on the board, but due to variations in connectors this isn't used in this case. Most likely this board was already replaced once? As the connector on the fan cable is bigger then the connector on the board, requiring the old hackjob.

 

Thanks for clearing that up! I'm way too new to know about all the little changes over the years :)

 

The fan could be power<->ground reversed, but that's fine, almost all fans do not care about this. And thus it's a mistake easily made by assembly.

 

True, it would not kill the printer - but it wouldn't run either so I'm just wondering what's going on.

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I really appreciate your help!

@Daid - glad to see you, even on this forum. The board is the original one, as it came to me at the February, 2014.

 

5V power regulator

Can you please point me to this thing? I have a multimeter device, so if someone could tell me what to check (and even better - what values to expect), I probably could do some board inspection.

On the more practical side - would newer boards fit my dinosaur? And where can I find ones?

Many thanks,

Alexander

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I have a multimeter device, so if someone could tell me what to check (and even better - what values to expect), I probably could do some board inspection.

 

Alright, as I said I think it's prudent to check if you have supply voltage before drawing any sort of conclusion. So hook up your board again and flip the power switch on.

This is the copper (back) side of the board:

5a3327c8600d8_UM2coppersidetestpoints.thumb.png.ef2f7575b1d64464ced963206d954664.png

Get your multimeter out, set it to measure DC voltage. Your common measuring pin goes on TP24, which is a ground. Then measure the test points for the fan and look for 24 volts DC. I can't remember which one it is - the silk screen with the test point numbers has an error on this board. One of the two should read 24 volts though, if your power supply is working and the power switch is closed.

If you can find this voltage, move on to measure TP16 next. That's the 5V output from the buck converter.

5a3327c8600d8_UM2coppersidetestpoints.thumb.png.ef2f7575b1d64464ced963206d954664.png

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I really appreciate your help!

@Daid - glad to see you, even on this forum. The board is the original one, as it came to me at the February, 2014.

 

5V power regulator

 

I think that since your Board is 2.1.1 someone did something very wrong when they did connect your 5V hotend fan. Clearly the fan should be on the 5V fan plug, that your board already has.

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I think that since your Board is 2.1.1 someone did something very wrong when they did connect your 5V hotend fan. Clearly the fan should be on the 5V fan plug, that your board already has.

 

Yeah that is very odd isn't it? Also I can't wrap my mind around why the polarity is like it is. Pin 1 is 5V and pin 2 is GND on the serial header, according to schematics.

Edited by Guest

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Well, as I said, the printer was always giving me some electric current since I got it, so something was clearly not 100% right with it from the very beginning. But it worked. And now it's not.

So, if the main board is cooked, as it most probably seems to be, I need a new one.

Would this one fit?

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