Printer stops
September 16, 2019 11:38AM
I have had an issue that has developed and gotten worse over the last 2-3 weeks. It started out that the printer just stopped occasionally (1 out of 10 or so) and wouldn't respond anymore. Now it is about every second time, with the likelyhood increasing the longer the print is. Yesterday I did 2 prints right after one another. It stopped after 10 seconds on the 2nd print. When the printer stops, it doesn't respond anymore. It seems like the hotend and bed loose power too.

This is what I have done to troubleshoot over the last 2 weeks while the issue was getting worse:
  • Change the USB cable
  • Change the USB port
  • Update pronterface to 2.0.0rc4
  • Try out different Marlin versions. 1.0 and 1.1RC8
  • Print from SD card

From my troubleshooting I think I have isolated the Melzi board to be the issue.
The heatbed connector burned through a few weeks before these issues have started to pop up. Because I didnt have a replacement I desoldered the heatbed connector and swapped it with the fan connector because that only uses one pin of the terminal.

I don't know how to further debug this issue. It could be anything. I have a Nano configured as ISP, an Altera USB Blaster (not sure if that helps - I think its ARM only), oscilloscope and multimeter. I hope something can be used to help pinpoint the issue.. Maybe it is even something dumb like a power connector that is loose. I just don't know how to pinpoint the issue...
Re: Printer stops
September 16, 2019 01:12PM
Perhaps monitor the 12V in at the terminal screws and see if the power dips or has excessive ripple on it. Could be the PSU going bad due to the capacitors wearing out. Also check the 5V rail is actually 5V.

Re: Printer stops
September 22, 2019 10:04AM
So there seem to be 2 different scenarios:
  1. Printer stops -> Heaters switch off. The cause for this was a loose connection on the power supply. I noticed by monitoring the power pins with the osci.
  2. Printer stops/pauses and heaters stay on. It is less frequent, but I am still scratching my head on this one.

Should I monitor the 5V rail between the GND and 5V pins on the EXT or the ISP pin header?
Re: Printer stops
September 22, 2019 11:59AM
It shouldn't matter where you measure the 5V as they are all connected together. I think the easiest is on the jumper that selects between regulated power and USB power.

Most likely all your problems are bad power connections. If the PSU ground is not good it causes bed current to flow down the USB cable and that will cause the USB connection to drop out.

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