UM2+ not working - Help!

[Jaamb 0]

 

Hi,

 

I have an UM2+ which has stopped working. Went to use it, power on, flipped the switch - nothing happening.

 

I’ve searched online and found a few posts on this forum where other people have had issues with their printers not starting up.

 

The power pack is working fine with the blue LED glowing. I’ve removed the motherboard and tried unplugging each plug and switching it on/off (as suggested on a different post). 

Still nothing happening.

 

Does anybody have any further suggestions?

 

Thanks

 

[stu_le_brew 42]

I would check the output from the power supply with a voltmeter to the plug for the printer

 

S

[Jaamb 0]

Thanks @stu_le_brew

 

Checked this out with a voltmeter and is fine.

 

I should have mentioned in my original post, the board does have slight discolouration from heat but nothing appears burnt out.

 

I’m just making sure i’ve checked everything I can before having to buy a new motherboard 😩

[gr5 2,173]

Those power bricks have a high failure rate.  I'd make sure there really is 24V on the actual main board.  And not just on the connector when not plugged in.

 

Of course if there is a short on the board, the power might be 0V on the board even though the power brick is working.

 

Also fully power down the brick until that blue light goes out.  That can take many hours if there is no load so try it with with brick connected to the UM motherboard.  I've had bricks that won't do anything even with the blue light but if you leave it long enough for the blue light to go out (again - could be many hours - even 24 hours) and then boot the brick back up it suddenly starts working fine.

 

But my money is on the motherboard being the problem.

[Jaamb 0]

 

Ok, thank you - i’ll give those suggestions a try.

[Jaamb 0]

@gr5 So i’ve gone through your suggestions - tested the board and there is voltage showing.

When the switch on the UM is in the off position voltage is detected but when switched to the on position this goes to zero. 

 

Also left the brick to power down and plugged back in but unfortunately still nothing. 

 

 

 

 

[Torgeir 242]

Hi @Jaamb,

 

This latter information do not make sense and made me think here is something more to check.

 

As you measure power (present voltage) at the switch before switching on, the voltage should be present in on position as well..  I'll presume that the blue (or green) power light on the power supply is still present when printer is switched on, right?  There is no reason that the voltage should drop, unless there's is a weak point in the feeding circuit to this switch.

 

The question is, are you measuring the voltage on the input side (where the voltage come from the power supply) or on the output side of the switch?

 

Well, -cause there is normally voltage present at both side of this switch when the main PCB is not working.

 

We're talking about 24 VDC from the external power supply.

 

Thanks

Torgeir

 

 

 

[gr5 2,173]

It could well be that one of the chips on the board (or somewhere else) is shorting.  Or it could be the power brick.  I happen to have an IR camera that can spot hot chips but you could try your fingers.  That supply can in theory put out over 100 watts which would make smoke.  In practice it probably would detect the short.  But still - something might be getting hot enough to feel it.

 

I'm an electrical engineer so I would do two tests:

1) Put a load on the supply.  When you first turn things on - when you don't enable heaters or steppers - it should not draw much.  Maybe a half amp.  So that would be about 50 ohms.  That 50 ohm resistor will receive 11 watts so unless it is a high wattage resistor, only power up for less than a second but check the voltage during that half second.  Also check to see how hot that resistor gets in one second (hot!).

 

2) Test the board without the supply:

Use an alternate 24V supply that can supply at least 10 watts (not enough for servos and heaters but enough to boot up the rest)

 

3) Alternatively measure the current.  If you have a current meter that can handle 20 amps or so (who does?) then break out the circuit and pass one leg through the ammeter.  Expect only about .1 to .5 amps.  20 amps means there is a short on the board.  0 amps means your ammeter just blew it's fuse (happens to me all the time) or the brick is bad.