Hot bed not working, no output.

[cjdavis618]

I have my machine built and starting to test all the functions of the machine. Have the Repetier host running and can read temps from both Extruder 1 and the heat bed. I can also heat the extruder up and see the temp change. (As well as get voltage readings from it). All Axis directions, fan controls, etc work. Although LCD hasn't been installed yet because I am waiting on connectors since my kit shipped before the adapter announcement by a couple of days.

For whatever reason, I cannot get any power through the rambo board to the heatbead. I have verified the input voltage but when enabled through repetier, I get no voltage output, nor any LED action. I have verified polarity and no issues there.

I have read some posts about firmware updates and checking pins, but frankly I am lost on that still and don't know where to get that corrected. I have downloaded the Arduino IDE and also downloaded the Johnoly and Polygonhell firmwares, but that is where my fun ends. I have searched around here and don't really see a step by step on firmware uploads or any backups for the rambo boards and I don't want to screw this up on my first attempt.

Can somebody point me in the right direction please? It will be much appreciated.

[mhackney]

My advice is to upload Polygonhell's firmware. However, I'm guessing you have the version 1.1 RAMBo that is 16 micro steps. Read/search my build thread for the exact edit you need to make in configuration.h. Then upload the firmware. Your problem is likely a misconfiguration of pin assignments in Johns firmware polygonhell's is "known good".

I posted a reasonably detailed description of how to use the Arduino IDE to upload firmware. You should be able to find it with a quick search.

[Polygonhell]

If the light isn't working, most likely you have no power on the heated bed circuit, make sure you have 12V going to each of the 3 inputs, then check the voltage at the heated bed fuse, ensure it's OK, I believe they changed the fuse on 1.1 from the 1.0 resetable fuse.
Most likely there was a short at some point and the fuse blew.

[cjdavis618]

I have already checked the voltage at the board at the terminal screws. and at the back of the terminal header on the inputs side and get full voltage. (On all 3 Legs) I know that the board is recieving the power from the supply but nothing is coming out of the other side. Like I mentioned in the first post. Fan and extruder controls allow power out of the other outputs and measure correctly with my fluke 289 meter. The Hotbed doesn't. But, I do have temp readings that are reading correctly for the environment. So it doesn't appear to be a thermistor issue.

I did get John's file to upload for me a moment ago but still the same issue. I think I got a bit further on the Arduino IDE but still wouldn't claim to know anything there. I just uploaded Poly's firmware and get the same thing. Fuses are checking out with a continuity check.

Could it be a bad board?

[mhackney]

Do you see the red LED on the RAMBo come on when the heat bed is supposed to be heating up?

Any chance you could post a clear photo of the RAMBo so we can verify connections to the correct terminals?

When I first set mine up, I had intentionally left the hot end thermistor detached. Turns out the heated bed output is disabled of the hot end thermistor is not hooked up. I know you said you get reasonable readings on both, just wanted to mention in case you may have disconnected for some reason.

[cjdavis618]

I don't see any red lights when Heat bed is activated, but I do when the Extruder is turned on.

Photo attached upside down, but here it is.. lol

[mhackney]

Looks fine. Did you check the fuse as Polygonhell suggested?

[cjdavis618]

Both the 15amp and the smaller fuses check out with my continuity check on the meter. That is why I am lost. I pulled the firmware straight from Github and compiled and uploaded them both and same result. Even made sure the machine was shut down between uploads to see if a reset helped. No joy..

[Polygonhell]

The reason you need to check the fuse is because the RAMBO board has 3 completely independent fused circuits and one is exclusively for the heated bed, so if it blows it's the only thing that doesn't work.
It's the 15A automotive fuse in the picture.

[cjdavis618]

Poly, I have checked them and they are all good. I worked in car audio for years and have seen all kinds of fuses in my life so that was the first thing I checked. Software is not my forte but PC hardware I can get around pretty well with as well. The 15 Amp fuse is perfect, the other 2 fuses beside the header are working as well.

I'm getting 12.56~59v on both sides of the 15amp when powered on.

[Polygonhell]

The next thing to check is the logic line to the MOSFET to see if it goes high when you think the bed should be on.

[cjdavis618]

I don't have tools to check logic. Only voltage, but if you are asking about D7, I get no voltage on either side. On Q5, I get 5v on the far right side, but no other readings when it is activated or off.

I am using the manual controls in Repetier and also have tried it with the extruder on as well and no change. I'm assuming that LED6 should be lit when it comes on, correct?

Seems like that particular output would be better served with a pin driven relay rather than a solid state connection of that amperage, but I am not an EE. I do have lots of background with breakout boards and Parallel ports for Mach3 control though.

[cjdavis618]

Found the issue. I got to looking closely at the fuse holder for the 15 amp fuse and the holder was not soldered down to the board and was making a weak connection on the output side of the fuse. Guys, watch your solder joints on these boards, mine wasn't completed.

[mhackney]

Wow, good catch! That one goes in the old knowledge base/noodle.

Hopefully smooth sailing from here!