Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy? – Hardware, firmware and software help

DockGuy

(@dockguy)

Member

Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

When moving the X axis via PronterFace 1mm at a time, I get a "thud" from the Y-motor every 6th mm.

When running the X motor with no belt connected, the same noise reproduces. It seems that whenever the controller board outputs a signal to X, some signal is also being sent to Y. I confirmed this by disconnecting the Y motor from the board and the symptoms went away. Then I tried swapping the X and Y motor cables. The symptom followed the Einsy board output, NOT the motor. Disconnecting E, Z, heaters, thermistors, etc had no effect. The interference is only between X -> Y and only when the Y axis is stationary. I don't not hear the symptoms when both X and Y are moving, so there seems to only be disruption in straight lines along the X axis.

How can I further diagnose the issue? I suspect a surface mount capacitor next to one of the output drivers has failed causing disruption on neighboring drivers but its been too long since my EE courses in University - I don't know where to start.

Printer is out of warranty and I'd hate to waste a 99% function Einsy board.

Posted : 14/03/2020 10:53 pm

DockGuy

(@dockguy)

Member

Topic starter answered:

RE: Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

According to the MiniRambo 1.3a schematic, X and Y circuits are tied together via the [XY-REF] PWM signal - this regulates the current to the motors. The PWM signal comes from the ATMega MCU, then through a cascade style 2nd-order low-pass filter and then fans out to both X and Y A4982 driver chips.

https://www.allegromicro.com/~/media/Files/Datasheets/A4982-Datasheet.ashx

I reckon the most likely cause of this symptom is that the Y driver chip overheated at some point in the past and is unable to manage outputting high current to hold the Y motor stationary when the XY-REF changes past some threshold. I will see if I can reproduce with Silent/stealth mode vs normal power mode - I suspect if I switch to silent it won't reproduce any more. But crash detection is off for Silent mode which complicates matters for a production printer.

If I can't figure anything out, I will see about getting a spare A4982 and solder it in. I have a hot air reflow gun, but not much experience with SMT chips. I'll report my findings if/when I try this.

Posted : 15/03/2020 4:35 am

rmm200

(@rmm200)

Noble Member

RE: Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

I am in awe of people who dig into electronic problems this deeply!

My ability to modify circuits pretty much ended when SMT came in.

Keep us posted on how it goes!

Posted : 15/03/2020 6:17 am

DockGuy

(@dockguy)

Member

Topic starter answered:

RE: Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

BTW, I posted this in the wrong forum - My board is the MiniRambo for the Mk2.x, not the Einsy board for the Mk3/Mk3s.

Although it seems similar issues can happen on the Einsy boards since they are using a similar VREF scheme. Here is a video of a Mk3 exhibiting similar symptoms as my Mk2.5:

Here is the $3 chip that could be replaced on the Mk2.x boards: https://www.digikey.com/number/en/allegro-microsystems/620/A4982/76950?k=&pkeyword=&sv=0&pv7=2&sf=0&FV=16%7C188846&quantity=&ColumnSort=0&page=1&pageSize=25&bpn=620-76950

This post was modified 5 years ago by DockGuy

Posted : 15/03/2020 6:55 pm

rmm200

(@rmm200)

Noble Member

RE: Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

Replaced by you maybe.

I would not attempt that without a reflow setup...

Posted : 15/03/2020 6:57 pm

DockGuy

(@dockguy)

Member

Topic starter answered:

RE: Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

@robert-rmm200

Does a toaster oven, a paint stripper heat gun, and a metal funnel count?

🙂

Posted : 15/03/2020 7:03 pm

rmm200

(@rmm200)

Noble Member

RE: Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

There again - maybe for you. That little sucker has 8 folded-under pins on a side.

That is too much like a ball grid array.

Now if the pins were folded out - I could have a go at it.

I have seen some impressive YouTube videos on low cost approaches. Get it hot enough and the part floats into place.

Solder paste is great stuff.

Just above my pay grade.

Posted : 15/03/2020 7:27 pm

DockGuy

(@dockguy)

Member

Topic starter answered:

RE: Crosstalk between X and Y - Signal to X causing noise (clicks/thuds) on Y channel - failed component on Einsy?

Well, I am now able to reproduce this on two Mk2.5 printers. On the second printer I can feel the Y-motor struggle to hold its position when the X axis moves. This printer also has audible issues when moving the Y axis slowly while the X-axis moves fast.

Its almost like the Y motor isn't getting enough power. I'm 99% sure that a component on the board has drifted off spec. I think this can be solved with an off-board motor driver. Maybe its time to upgrade the Mk2.5 to trinamic drivers:

https://forum.prusa3d.com/forum/original-prusa-i3-mk2-s-hardware-firmware-and-software-help/an-overview-on-tmc2130-upgrades-for-the-mk2-mk2s-and-mk2.5/

Posted : 05/04/2020 4:31 am

DockGuy

(@dockguy)

Member

Topic starter answered:

Long-term update on Mk2.5 Y-axis thuds during X-moves

So I never bothered modifying the Mk2.x MiniRambo 1.3a boards or convert to trinamic drivers as I had proposed. When I ran some printing tests to isolate x-axis and y-axis movements, I found that the thumping didn't actually cause printing artifacts so why not leave it well-enough alone?

Well over year later and its still working just fine and churning out great-looking prints. If/when things get bad, I will probably swap out the miniRambo for the Einsy or a similar board that runs at 24V and just keep running the heatbed at 12V with the original PSU.

Posted : 31/08/2021 3:46 pm