Help with sanguinololu 1.3

Hi,

After what seemed like an age of wiring up the printer and general testing, rewiring and testing again I made the mistake of powering it up with the 12V PSU the wrong way, unmarked screw terminals and a very basic error later and now the board seems dead.

Well that might be an exaggeration but the light comes on, I can upload firmware and the thermistors appear to work but the steppers and heaters will not. I've tried using repsnapper as a manual control for the steppers and heater. this did work before and now does not. I've double checked all connections and they seem fine too. repsnapper appears to be communicating as it gives me the thermistor reading as a fluctuating value around 17deg (seems reasonable!)

What have I most likely broken and is there an order to the trouble shooting?

I'm handy with a soldering iron and know how to use a multimeter and oscilloscope but would like a hit list for what Ive most likely damaged.

Many thanks!

There's a good chance you have killed the mosfets and the pololu's, if you have spares I would recommend you swap them out and see if that helps.

Yeah I thought that was likely to be the case, I am pretty certain that the stepper drivers are dead, does anyone know if it will just be the chip that dies or will I have blown any capacitors? The board has no visual damage which i guess is good! And I have a spare mosfet but not polous. Basically I I want to collect a pessimistic BOM for the repair as the postage cost it likely to be close to the cost of the parts and I don't want to place 2 orders. And I take it that the LM7805 should still be ok?

Edited 1 time(s). Last edit at 12/04/2011 08:14PM by yellow_fish.

Right well after replacing the LM7805 and the Mosfets I now have a very strange new problem. With the Amtel installed but no stepper drivers the 5V line when powered by the 12V PSU are reading 10V, then the Mega got toasty and now appears dead as it will not connect to the (although it is still recognising the USB so seems like the FTDI is still ok) Is this likely to be caused by the Amtel dying beforehand and only now giving weird voltages out? The reason im not convinced is that when running of the USB before I did any repairs the printer was connecting through RepG.

Little bit confused and dont really know how to find the root cause of the problems!

You should check your voltage regulator: I don't know the specs for the microprocessor, but if you supplied 10V instead of 5V, that may explain why it blew. USB provides ~5V, and a low current, so it probably wouldn't have blown before you plugged in the 12V power supply. Are any signals being outputted from the microprocessor?

If you reversed the polarity on the board, there's the possibility that you blew capacitors, ICs (i,e, voltage regulator), etc. If you can replace the voltage regulator (if necessary), then verify that you are supplying 5V to the appropriate devices, then you could install a new microcontroller and write a little program to test the pin outputs... if you can convince yourself the FTDI and controller are working, you can hunt for problems elsewhere (stepper drivers, etc)

Right well I've finally had a chance to fix things, hopefully this list will speed up the repair of others although I personally think that v1.4 should have polarity protection of at least the Stepper Drivers since they were by far the most expensive parts to replace.

What I killed:

2x Mosfets,
1x LM7805 vReg
1x AMTEGA664P (this gave the 10v on the 5v line, chip removed and the 5v happily sat at 4.97v again)
4x A4988 Pololus

All polarised capacitors were fine, although I would recommend that if you are unsure then replace them.

I have also changed the screw terminal to a plug to ensure that polarity is always correct.

I will also point out that initially the ATMEGA664P appeared to work although after being left for a week and turn on again it did not. This doesn't really make sense to be but I guess my point is that you almost certainly do need to replace it as well even if it appears to work initially.

Hopefully this post might speed someone else up on repairing their board as there seemed to be a few people who made the same mistake.

Hi,

Can anyone help trouble shoot my new Prusa build?

I have a LMU8 Sanguinololu set up and have just powered up, checked all connections before powering, no problems.

Checked how the Axis move and they are all free. I am using the Pronterface software.

The problem I have is how the motors behave.

The X axis works well but only in the + positive direction

The Y axis works well but only in the + positive direction

The Z axis tries but can't seem to move

The extruder motor works well on both directions but the wrong way.

The motors are wired as per the Wiki drawing, Red Blue Green Black

Thanks for any help

Ray