RUMBA board shorting out

[Mjolinor]

I missed a bit somewhere, I didn't realise you had plugged it in again.

You will get 0 now it has blown. It needed measuring before you plugged them together.

[Mjolinor]

From the schematic it seems fairly easy to forget the 16U2 USB <> serial and go in directly to the RX TX liines. I have done that on my Wanhao for the same reasons, the USB stopped working. I will replace the Atmega eventually but for now I just pick up the lines going to the main processor.

http://reprap.org/mediawiki/images/2...SCHEMATICS.png

From that picture all you need to do is get one of the USB serial thigns shown here:
http://www.geeetech.com/iduino-due-p...ter-p-655.html

The small board (DUE Pro USB/Serial), not the big one, they are usually on ebay but I can't find one right now.

Lift R17 and R18, solder a wire to one end of each of those resistors and solder the resistor back onto the side going to the main micro.

USB will then work again using the new USB<>serial adapter.

[stridera]

Nice. I found this: http://www.ebay.com/itm/Iduino-DUE-P...-/251753695359

Now, how to figure out which resistor on the board is r17/18. (No silkscreening on it.)

I do see a COM header, as well as a JTAB, but no clue what that is.

I wonder if I can hook into either of those.

When I tested before it blew, I didn't get anything significant. (Maybe 1-2microvolts, nothing more than I get when I wave the probes through the air.)

I also just ordered a couple more ATMEGA16U2-AU chips and I'll have to break out my reflow air solder unit to replace it. Hopefully none of the caps/resistors are blown.

[Mjolinor]

I noticed that on the pictures. Buzz it out form pins 8 and 9 on the 16U2 and 3 and 2 on the 2560.

http://reprap.org/wiki/File:RRD-RUMBA_PCB.PNG

That has them marked so maybe your PCB does but you can see where they are easily enough, bottom left of the picture just to the right of the USB.

[Mjolinor]

You can hook into the COM header but you have to change the software to make it do that I think (not really sure) and as you can't change the software easily without a programmer it probably isn't worth the hastle.

[stridera]

I just noticed from the latest PCB layout that it is JTAG and not JTAB. (heh)

I already have a programmer that I could probably just hook up. That would let me reprogram it, but it probably wouldn't help me as far as controlling the printer from octoprint.

I did order the ATMEGA16U2-AU chip, so when that arrives I can try to replace it. Not sure about the rest of the components though.

Thanks for all the help though. It has given me ideas of how to move forward. Not sure about the root cause, but maybe I can figure out how to get it up and going again w/o buying a new board.

[Mjolinor]

If you are using a Raspi to talk to it then you don't need the serial <> usb.

Use the serial port on the RASPI to connect to those two lines. Check the levels before you do, I am not sure if RUMBA serial lines are 5 volt tolerant or not.

[tsteever]

I have a Rumba and a Raspberry and no troubles. There has to be something that you are using that no one else is. My thoughts again return to your USB hub. I am not using a hub and have had no troubles. Are you still using that hub?

[BLKKROW]

Are you still using the USB Hub?

You may have an issue with your Motherboard or USB port if you are directly plugging it into your Mobo and not the Hub.

[stridera]

I haven't even got this one near my hub. It's only been plugged into the raspberry pi which was plugged into the same power strip as the printer.

When I first plugged it in, Octoprint worked fine and I was able to control the printer. I got it all setup, got the camera going and everything looked good.

I turned off my printer and turned it back on, which fried the usb port of the rumba and killed the pi.