My Mendel90 was not in use for about 1.5years and finally I wanted to use my 3d printer again.

I use the printer with octoprint and was able to connect to the printer, move the nozzle, heat it up and extract PLA... so far so good. Then I started heating the heatbed and everything froze So I had to turn it off and on again.

I connected the printer to my PC and tried to use printrun (still the version I got with the printer ) I could connect but no command worked
In the logging terminal these lines are repeating constantly until i disconnect the printer again:
----
Printer is now online.
echo:Marlin: 1.0.0 RC2
echo: Last Updated: Mar 23 2015 19:19:12 | Author: nophead
echo: Free Memory: 12982 PlannerBufferBytes: 1232
echo:Using Default settings:
start
----

now it's getting weirder:
I can't boot my raspberry pi with power from the power supply anymore, i now have to use an external power supply to boot the raspberry pi. But, If I put the micro usb connector (powering from the mendel90 psu) into the rasberry pi (still, no led on the pi light up) I am able to connect to the mendel90 with my pc and printrun (but still no function and the repeating terminal output). If I don't put the micro usb cable into the pi, I can't connect to the mendel90 with printrun. There are no other cables connected to the pi!

So far I only checked if 12v is still there for the printer board, and this is fine. And booted up the machine without powering the heatbed, but no luck. Any idea where to check next what is wrong?

Edited 2 time(s). Last edit at 06/07/2020 07:46AM by gribble.

Today I did some more testing...

When I started the printer the raspberry pi didn't start. I normally power the pi from the same PSU as the printer. So i unplugged the pi from the power supply.

I connected the printer to my PC and was able to connect it with pronterface. I can move the heatbed and the printhead, was able to heat it to 185C and extrude some plastic. But when I try to heat the heatbed the printer got disconnected after a few seconds (temperature rised about 10C) and I got the following output:
------
Connecting...
start
Printer is now online.
echo:Marlin: 1.0.0 RC2
echo: Last Updated: Mar 23 2015 19:19:12 | Author: nophead
echo: Free Memory: 12982 PlannerBufferBytes: 1232
echo:Using Default settings:
echoD card ok
Setting hotend temperature to 185.000000 degrees Celsius.
Extruding 5.000000mm of filament.
Extruding 5.000000mm of filament.
Extruding 5.000000mm of filament.
Extruding 5.000000mm of filament.
Extruding 5.000000mm of filament.
Setting bed temperature to 60.000000 degrees Celsius.
Can't read from printer (disconnected?).
Can't write to printer (disconnected?).
Can't write to printer (disconnected?).
Can't write to printer (disconnected?).
Can't write to printer (disconnected?).
-----

I have to replug the printer into my PC usb port and can connect again .. but the output of my tests are the same.

So again I tried to boot the raspberry pi and wanted to see what octoprint will say. As I stated I can't start the pi with the PSU and I had to use a second power source for the pi. But I cannot connect to the printer from octoprint:
------
State: Error: Failed to autodetect serial port, please set it manually.
------
I had a look at the dmsg output on the pi and the printer does not get recognized when I connect the USB cable. Other USB devices got recognized just fine.

Any idea what to check next? Looks like some kind of power problem to me. Raspberry Pi / Octoprint is not so important in the beginning, I am fine with printing from my PC as a start. Does the heatbeat drain to much power and the the melzi board resets?

Check that the ground connection on the Melzi terminal is tight. Classic sign of it being a bad connection is the bed current flows down the USB lead and causes a disconnect.

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[www.hydraraptor.blogspot.com]

Thx for the tipp.. just did a quick check and also rewired the ground connection .. no luck, even worse, now windows doesn't recognize the printer anymore

I am away on vacation now for two weeks, hope I have the right thought what to do next when I am back.

When the terminals are loose and drop some voltage they get very hot and can affect the PCB solder joints. It's a good idea to look at the back of the board and perhaps re-solder them.

Hard to see how tightening them could make it worse otherwise.

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[www.hydraraptor.blogspot.com]