Solved RAMPS board, LED2 shows intermittent cutout of voltage.

Hi ev1,

I began having trouble recently with the heated bed cutting out intermittently. I've discovered that the fan which was mounted on the board had stopped working, and two of the heat sinks had fallen off of the X and Y Pololu boards, which is a bad thing. I turned the printer on it's side and asked it to heat the print bed. That's when I noticed the LED would cut out and come back on. At first I tried playing with the wire to the bed (I know, that's like shaking someone's foot instead of their hand) thinking there might be some feedback issue with the thermistor wires. But I don't think that's it. I put a voltmeter on the power lugs to the heat bed and saw that the power cuts out when the LED does. Now I think the damn RAMPS board overheated. Any ideas as to troubleshooting steps I can take so I don't waste time waiting for a new board in the event that's not the cause?

 

And this would affect power to the heated bed?

 

Much appreciated Mark. I've found several of the RAMPS board pinout diagrams online and they all seem to agree with yours. I've just ordered a new RAMPS board and a 5 pack of the Pololus. Why screw around, huh? BTW I found your post on adding a fan to the front of the case and that is precisely what I'll be doing while waiting for the parts. Noise? I WANT it to make noise, that way I'll know if the fan fails. I run my NOCs by ear as much as anything else, always have.

 

yea, I've toyed with the idea of just buying all the extra parts. Building a robo3d minus the housing is 50-100 bucks. ... well.. the choice parts anyway

 

Well if the polyfuse is tripping out it could exhibit similar behavior. Otherwise it might just be the controller telling it to shutoff.

I think this is the image mark was taking about:

 

Power supply: I'm getting 10 amps and 12v approximately from each read/black. Is that normal?

 

Ok thanks Mark and Mike (hey that could be a show). I found the problem. I had inadvertently shorted two pins on one of the pololu boards when I glued the heat sink on. I removed it, reattached it, and now it all comes up fine.

 

Update: The stepper from adafruit seems to be working fine, except that it gets a lot warmer than the old one did. However, the steppers in the bottom are also running a bit warm. Since I never checked this before the changeout, I don't know if that's different. I will say that the adafruit stepper has a lower profile, therefore less metal to dissipate heat. It did not seem to affect the print at all (about 2.5 hours long).

Another issue that I have back burnered until now is that the new RAMPS board does not power the arduino. Currently I have to plug in a USB cable from my nearby workstation to do that. I'm able to use the LCD control and it's card reader. Real head scratcher, but easily enough solved if I wire in a power lead to the DC bus and plug it into the arduino. It's just a little concerning that the arduino doesn't power up when I switch on the AC power without the USB being plugged in. Perhaps some input from others who have been down this road will help not only me, but others who find this thread...

 

Well that was foolish of me....

 

I'm on it, and thanks for the heads up about 24v. I don't plan on changing that.

 

If I'm seeing the Arduino's LED turn on underneath the RAMPS board, but still not establishing a USB connection to my computer with a USB cable missing the VCC & GND connections, I'm guessing it's to do with a missing diode for D1? I'm just surprised to see this behavior; unless I'm missing some critical understanding of how the Arduino is powered through the USB bus...but still seeing it's LED turn on. Weird.