Pinda connector with 4 pins instead of 3 ???  

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MrMik
(@mrmik)
Honorable Member

I just removed the PINDA from my MK3 because of a presumed cable break.

For the past few months, I started each print by manually pushing the cable bundle when the extruder is on the right side of the bed, to prevent the PINDA cable loosing contact completely during the calibration. After the calibration, the PINDA does nothing, so the bit of extra manual effort was not too inconvenient, I usually watch the first layer anyway, and my prints are typically 12-20hrs long.

However, a couple of days ago this manual nursing along did no longer work. I thought I found that the PINDA cable has a partial break a couple of cm away from the stiff part coming out of the extruder. Because I had a supposedly working spare PINDA, I figured I best replace it. So I took the cable bundle apart, installed the new PINDA, and crashed the nozzle into the bed during the self test.

It turns out that the new PINDA does not work. No light comes on.

When I tried to check what is wrong with the new PINDA, I found that it has a 4 pin connector, with a white cable that is not present in the 3-pin connector on the PINDA that came with the MK3 printer. I also have another used PINDA from the MK2 printer, it also has 3 pins instead of 4 pins.

The baffling problem I have now is that the connector on the MK3 circuit board is actually a 4 pin connector, and the PINDA with 4 pin connector clicks in nicely as it should. But, the original PINDA that came with the MK3 printer, and the other PINDA with 3 pins will not fit any longer into the 4-pin socket on the MK3 circuit board. It appears as though a piece of plastic has snapped off, on the left side of the connector socket, which may have somehow helped to hold the 3-pin connectors in the 4-pin socket.

Questions:
1) Why is the 4-pin PINDA not working? It appears to click in well, and the three cables (other than the white one) connect to the same pins that the 3-pin PINDA cables connect to.
2) How can I best fix this? A drop of hot glue to keep the 3-pin PINDA in place comes to mind, but could get messy when the next cable break occurs and I need to take it apart again.

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Posted : 25/08/2018 2:18 pm
RHDreambox
(@rhdreambox)
Prominent Member

Is your PINDA connected like this, and does it not respond if you hold a metal object against the PINDA sensor?

Bear MK3 with Bondtech extruder...
Posted : 25/08/2018 3:57 pm
MrMik
(@mrmik)
Honorable Member


Is your PINDA connected like this, and does it not respond if you hold a metal object against the PINDA sensor?

It is connected like this, and there is no response when metal comes close to it, because the light is not on in the first place.

Where did you find that photo?

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Posted : 25/08/2018 11:24 pm
RHDreambox
(@rhdreambox)
Prominent Member

The picture is in the MK3 kit assembly manual part "8. Electronics assembly"
https://manual.prusa3d.com/Guide/8.+Electronics+assembly/513?lang=en

It seems that the PINDA cable is very sensitive to cable breaks. Could you possibly have damaged it during assembly? Do you have any ability to measure the cables?

Bear MK3 with Bondtech extruder...
Posted : 26/08/2018 11:26 am
MrMik
(@mrmik)
Honorable Member

Strange that they have a 4 pin connector on the board and in the manual pictures, but ship a 3-pin terminated PINDA.

I have no idea how I convinced myself that the PINDA 3-pin cable was plugged in properly when I initially assembled the MK3. There seems to be no way to do it again without cutting off the clip part on the male 3-pin connector. Once I did cut off the snap-in clip thing today, the 3-pin connector slid in as it should. It just does not click, but it's secure enough.

And now the PINDA probe works again, with the same un-repaired cable that I thought had a break in it.
The root cause of the problem was probably a shoddy intermittent connection of the 3-pin plug in the 4-pin socket, all along.

The printer is running again, and I finally don't have to nurse it along during the calibration phase of a print.

It still evades my understanding why the (presumably new) PINDA probe with 4-pin connector does not work in the MK3 4-pin socket. I might have mistaken it for a new one, but it might in fact be a damaged PINDA left after some MK2 repair. However, it looks like new and I usually label broken parts as broken before storing them and eventually throwing them out.

I print a lot of large thin objects (surfboard fins) diagonally across the entire print bed. They are thin but use (almost) the entire X and Y range on the majority of layers. A stress test for cable breaks!

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Posted : 26/08/2018 12:00 pm
RHDreambox
(@rhdreambox)
Prominent Member

It's nice that your printer is working again.
It was strange this with the PINDA sensor. The first printers that were delivered had another PINDA sensor, but I do not know if it only had 3 connections.
But I cross my fingers every day to not have a cable break 😆

Bear MK3 with Bondtech extruder...
Posted : 26/08/2018 12:26 pm
MrMik
(@mrmik)
Honorable Member

Thanks for your help, and may your cables always be of sufficient continuity..... 😛

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Posted : 26/08/2018 1:00 pm
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