Hi guys!
This weekend, I replaced the Melzi on my parents' Mendel. This is all I ever did to the new Melzi:
Motors and hotend worked fine, but when I switched the heatbed on, I got a disconnect. I rebooted my laptop (because of software updates) and hooked the USB cable back in. That's when the CPU melted. Quite fast.
I understand that a fuse in the USB port should have saved the CPU, but I don't know why I got this large current (> 0.5 A) from the Melzi when switching on the heatbed. The only thing I have found on the subject is this: [forums.reprap.org] and this: [reprappro.com] On Friday, I will step through the little RepRappro guide.
EDIT 1: Also found budjar and nopheads conversation hidden in this thread: [forums.reprap.org] suggesting that a bad ground connection could be the error source. I actually double checked that resistance to PSU ground was ok before commisioning, but I have no firm definition of 'good enough', I just measured a < 2 ohm resistance. Could bad ground still be the cause?
Do you have suggestions on where I should point my multimeter? Has the same happened to you, or have you heard about incidents like this before? I feel like I have to understand this incident before I can continue my RepRap adventures :-|
This weekend, I replaced the Melzi on my parents' Mendel. This is all I ever did to the new Melzi:
- Wired up
- Adjusted trim pots
- Uploaded RepRappro Marlin
- Connected with Pronterface
Motors and hotend worked fine, but when I switched the heatbed on, I got a disconnect. I rebooted my laptop (because of software updates) and hooked the USB cable back in. That's when the CPU melted. Quite fast.
I understand that a fuse in the USB port should have saved the CPU, but I don't know why I got this large current (> 0.5 A) from the Melzi when switching on the heatbed. The only thing I have found on the subject is this: [forums.reprap.org] and this: [reprappro.com] On Friday, I will step through the little RepRappro guide.
EDIT 1: Also found budjar and nopheads conversation hidden in this thread: [forums.reprap.org] suggesting that a bad ground connection could be the error source. I actually double checked that resistance to PSU ground was ok before commisioning, but I have no firm definition of 'good enough', I just measured a < 2 ohm resistance. Could bad ground still be the cause?
Do you have suggestions on where I should point my multimeter? Has the same happened to you, or have you heard about incidents like this before? I feel like I have to understand this incident before I can continue my RepRap adventures :-|