VSSA error quesion



  • Hello guys,
    I'am an user od Duet Wifi and would like to thank you for your great work and well projected board. I'm a reader of this forum from a long time now but newer had a reason to register yet. So this is my first post.

    Unfortunately after upgrading to RRF 3 I'm having some problems (had some hardware changes also at the same time so I'm not really sure what is going on.
    I'm getting random VSSA errors that cannot find source. All the tem sensors shut off for a short amount of time some time slice of a second sometimes for a longer time (few seconts). It looks like the VSSA gets current from somewhere and the VSSA fuse shut off and then switch on again. Most of the time its miliseconds but one time it showed -273 deg for some second on the all sensors (2extruders+4beds). Unfortunately I wasn't able to found out the cause, wiring seems to be ok, and it didn't do that before RRF3. With the upgrade I changed one of the extruder heaters due to bad wiring near the heating cardridge. Do not see any problems there/
    So my questions are.
    Is it possible that VSSA erros like that can be caused by changing to RRF3 or may it by caused by induction somewhere in the sensors wiring that is close to for example power wiring?

    Thanks



  • I am not sure but I think I'm getting some progress there.
    Yesterday I've mounted additional ferrite filters on the cables (power lines and signal aso) and since then I did not noticed any VSSA error yet. I don't know if that helped but it seems so. Maybe the EMI or power induction was the cause?
    Or maybe somethig is not working on the boart, filtering is bad or something?
    Any suggestions will be helpfull.
    Thanks


  • Moderator

    Do you have everything grounded?


  • administrators

    @xyzyx said in VSSA error quesion:

    Is it possible that VSSA erros like that can be caused by changing to RRF3 or may it by caused by induction somewhere in the sensors wiring that is close to for example power wiring?

    Most unlikely. We think that the usual cause of VSSA errors is a short between the VSSA side of a thermistor and a heater or fan connection. The short could be between the thermistor and the hot end metalwork, if there is also a short inside the heater cartridge between the element and the case.

    I am also aware of one instance in which the VSSA fuse has gone open circuit.



  • Yes. I have all grounded, but I will check again all from the start. Next if this issue will continue in the near feature I probably change (mount new) hotend wiring just to be sure thats everything is ok and no wires shorts to each other.
    I also don't belive that new firmware could do that. I didn't notice any shorts but the strange thing is that additional ferrite cores probably helped. Will see how it goes, I will let you know.



  • @dc42 said in VSSA error quesion:

    @xyzyx said in VSSA error quesion:

    Is it possible that VSSA erros like that can be caused by changing to RRF3 or may it by caused by induction somewhere in the sensors wiring that is close to for example power wiring?

    Most unlikely. We think that the usual cause of VSSA errors is a short between the VSSA side of a thermistor and a heater or fan connection. The short could be between the thermistor and the hot end metalwork, if there is also a short inside the heater cartridge between the element and the case.

    I am also aware of one instance in which the VSSA fuse has gone open circuit.

    Story gets more interesting. I was inspecting electronics till late night yesterday and I was suprised what I've found.
    First of all I opened PSU, which had bad PE connection (had to tighten the screw to the hasis), so it was not connected all the time like should and it was difficould to find this problem due to it was connecting properly for most of the time.
    But later I found out something more interesting which I belive may be the cause of the problems.
    When I swiched on the printer and when the heted bed started on heating whole unit reseted. I thought that I broke the PSU somehow but it works fine, only resets when heat bed starts. After investigating I found that HB has about 0.2-0.3 ohm so its shorted. After takin off the steel sheet I saw that there are few spot where the steel sheet shorts the HB traces and that make an ARC. I have a magnetic Heated bed where traces are on top and are coated/painted with a black paint of somekind. Seems that the coating is broke slightly in some spots and that shorts the bed traces with the still sheet. I even found tiny traces of ARC on the steelplate, eaten micro spots like when welding. After simply painting this spots with an oil marker just to check if it helps, the shorts are gone and HB works again. HB gives strange buzzing sound when driven (switched on and off) so it needs further invastigation, but the question is:

    Can ARC like that cause VSSA errors in your opinion? And is it possibile that ferrite helped with getting rid of these erors even with broken HB?
    I still didn't find any shorts to VSSA directly.


  • administrators

    Two possibilities I can think of:

    1. The arcs were causing enough electrical noise to trigger the VSSA warning;
    2. You have a short between the bed plate and the bed thermistor, so the arcs were feeding a voltage from the bed heater into VSSA directly.


  • Unfortunately it was not solved and problems mentioned above probably wasn't the cause. It seems that something wrong is with the hotend heater, just before the VSSA error it started to cooling down and then started to heat while made VSSA error (didn't see that behaviour before there was only VSSA errors).
    Maybe the new hotend heater that I've mounted is damadged and has internal shortage or arcs randomly.
    This is how it looks.

    vssa1.jpgvssa2.jpg


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