MELZI V2 board- Endstop still ON. strange ohm value
December 29, 2015 04:48AM
Hi all.

I assembled a Prusa i3 two days ago . So very very neat and I had a problem initializing the axis Z.

when I look closer at me I perceive that the end stop does not react at all. (whether connected to the card or not ).

and when I I compare the resistance of entry of other endstop is one that I have not run a big difference , as if there was short circuit.

I made this video:

What do you think? manufacturing defect mainboard ?

Many thanks ans sorry for my english ^^
Re: MELZI V2 board- Endstop still ON. strange ohm value
January 02, 2016 11:25PM
Assuming the end stops you speak of are micro switches when you hook an ohmmeter to its wires it should read infinity or open circuit and when you push down on it you should see a closed circuit or zero ohms.If this does not happen replace the micro switch. If you get a closed circuit without pushing on the switch and open when you press the switch it is wired wrong. Most micro switches have 3 terminals a Common an NC normally closed and an NO normally open and in most cases the Common and NO is used. Do these tests on an unplugged switch. I have had bad micros.
Re: MELZI V2 board- Endstop still ON. strange ohm value
January 03, 2016 05:10AM

Thanks for your answer.

So I resolved the problem yesterday night with this two shematics to help me.

schematics 1

schematics 2

the micro contact was tested OK.

so it was the micro capacitor c7 of 4.7uf was KO.

I tried a homing with the capacitor unsoldering and the printer was full ok.

So I get a new 4.7uf 16V capacitor on a old video transmiter (Im very lucky). Since this operation the printer is working very well.

I was a manufacturing defect of the board. The sticker "QC passed" is very funny!
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