ray.p
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I3 MK1 - Non responsive - No apparent power

Sun Feb 18, 2018 9:32 pm

My Mk1 has been chugging along for 2 years, and hasn't had much in the way of issues. The biggest one was the heatbed port on the Rambo board fried and generated some obnoxious smoke about a year ago. I replaced the board with a new board from utilmaker and was back in business.

This past week, after finishing a print, the heat bed wouldn't come back up to temp. The hotend would come up to temp just fine. No burning smell, everything seemed normal. After fiddling around - power off, power on, unplug, plug in), now the printer won't power up at all. Normally there is a green light on the board itself, but no light and the LCD screen doesn't light up either.

I've done the following:

- Continuity tester on the brown fuse next to the ports where the Power Supply wires come in - seems fine
- Continuity tester on the fuse in the plug on the power supply - seems fine
- Volt reading on each pair of wires coming from the power supply to the board read around 12v and change. I'm not deep into electronics, so I'm assuming that with 4 wires coming into the board, and each pair bringing 12v, that should be what is expected.

I had originally thought the power supply had died, but given the above, I'm not so sure.

Anybody have any thoughts or recommendations?

kevin.r5
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Re: I3 MK1 - Non responsive - No apparent power

Mon Feb 19, 2018 3:35 pm

752px-MiniRambo1.3a-connections.png
752px-MiniRambo1.3a-connections.png (342.24 KiB) Viewed 161 times

If you've got 12V at the ports labeled A and B, your power supply should be ok.

Did you check both of the brown fuses?

If F3 is ok and you have 12V at port B, you should have a power indicator lit on the Mini-Rambo board.
-Kevin

ray.p
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Re: I3 MK1 - Non responsive - No apparent power

Tue Feb 20, 2018 2:30 am

Thank you for that diagram. It will help for future reference.

I tested all the fuses for continuity. They all checked out fine. When putting everything back together to LCD started flashing. for whatever reason, the lack of all power might have occurred when I was messing around since I think I attempted to reseat the fuses initially and may have not reseated them completely.

I tested continuity at the heat bed as well as the wires going to the heat bed. all checked out fine.

I then assembled everything and got an initial red light on the heatbed, which I thought I was home free.

After getting everything back together, no red light to the heat bed.

Jiggling the wires going from the heat bed into the control box (which I tied down with a zip tie) flickered the red light. So at this point I'm thinking the issue is in the connector or the plug for the connector to the board.

I'm going to work on it again tomorrow. too late for undoing everything again. I'll have to look and see if I have an extra plug to try. I did crimp the end of the wires going into the plug with solid, shielded caps, and the connections still look sound. I might try redoing those to see it that helps, but I did check continuity going through the crimped caps.

ray.p
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Re: I3 MK1 - Non responsive - No apparent power

Sat Feb 24, 2018 3:50 am

Ok. Looks like I found my issue.

I was replacing the ferrule connectors on the ends of the bed leads and when I went re-strip one of the leads, about 2 inches of a few copper strands came out with the 1/2" of insulation. Looking back up the line, I found where one side of the leads had been partially severed, inside the wire wrap.

Not sure how that happened but now I just need to splice in new leads.

From looking at it, and referencing some online guides, it seems like the leads are 16AWG stranded wire.

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joan.t
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Re: I3 MK1 - Non responsive - No apparent power

Sat Feb 24, 2018 1:54 pm

Hi Ray,
considder replacing the wires rather than repairing them...
20180223_204530[2].jpg
20180223_204530[2].jpg (2.25 MiB) Viewed 83 times
the wires on the bottom are Prusa heat bed wires, the ones on the top are radio control model power wires.

the prusa wires have about 22 filaments which is more than most cables, but the RC ones have 252filaments and soft silicone rubber covering, making them much less likely to break again.

regards Joan
I try to make suggestions that I believe to be well founded and safe,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions,
what you do, is YOUR responsibility.

ray.p
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Re: I3 MK1 - Non responsive - No apparent power

Sat Feb 24, 2018 3:21 pm

Thanks for the reference. My only issue is that my soldering skills are rudimentary at best. I'll look for those wires since it would be nice to not have to worry about them breaking. 16AWG it looks like?

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