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  1. #1
    My Machine is a Heiz S1400 and until today it has been fairly trouble free, however during a cut today the x axis racked and stalled.

    I have twin steppers on the X axis and at first i thought i had narrowed it down to one of these steppers, however on switching over the control cables and seing the propblem move from one x axis stepper to the other i then realised it was an output problem frm the control box.

    I have taken the control box apart and the first thing i have noticed is what seems to be a circular crack in one of the driver chips TA8435HQ.

    Is this likely to be the culprit ?, all 3 other chips seem intact

    and if so does this need replacing with exactly the same chip as the others are TA8435HQ too.

    i am assuming this will be a relatively simple soldering job, just desolder the old one and replace?

    I will upload a picture of the chip in a minute

  2. #2
    Click image for larger version. 

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    Here are the pictures

  3. #3
    does this need replacing with exactly the same chip as the others are TA8435HQ too.
    Can't answer that but you can buy them here:-
    http://www.ebay.co.uk/itm/1PCS-TA843...-/251057536704

    I would also check the current rating you have set.
    Last edited by Clive S; 20-12-2016 at 06:33 PM.
    ..Clive

  4. #4
    GND's Avatar
    Lives in Cambridge, United Kingdom. Last Activity: 1 Week Ago Has been a member for 2-3 years. Has a total post count of 55. Received thanks 1 times, giving thanks to others 9 times.
    I'd say it's definitely the first thing to try - that driver chip is clearly dead! Looks from your photos like they are socketed though, so no soldering required. Just remove the old one and replace like-for-like, being careful not to bend any of the pins.

    Also, check to see if the chip needs to be electrically isolated from the heatsink. Some do, some don't - take your lead from what is currently there, and if the back of the chip is metal. If it needs to be isolated, then there will be evidence of an insulating pad or washer used between the chip and the heatsink, and then you need to take a lot of care when you fit it all together, testing it for isolation with a meter. But maybe it is just bolted together. Looks like there is at least some heatsink compound used, but what lurks in between is not visible in your photos. Try and salvage as much of that as you can for the new chip - ideally you'd buy a small tube off eBay and smear it on to help conduct heat from the new chip.

    Hope that helps!
    Graeme

  5. #5
    Thanks GND and Clive S. Yeah that will be handy if the chip is socketed, im crap at soldering to be fair. I think they are just bolted together with small bolts with thermal compund between the heatsink. I have a tube of MX4 Processor compound from building PC's so im thinking that would work.

    That chip definately is the one leading to the X axis output with the problem so i will replace it and see if that fixes it. There is one on ebay available from the uk but it is missing the Q designation at the end so not sure if it would be ok TA8435H rather than TA8435HQ. I will order one of the ones Clive suggested but might be a little wait for that one to arrive.

    regards
    Adam

  6. #6
    GND's Avatar
    Lives in Cambridge, United Kingdom. Last Activity: 1 Week Ago Has been a member for 2-3 years. Has a total post count of 55. Received thanks 1 times, giving thanks to others 9 times.
    I had a quick look at this device's datasheet, and the only difference between the H and the HQ versions seems to be that the HQ is tinned with lead based solder, so it's not "lead free" as is required these days for commercial use. But for your purposes it really makes no odds - go for either and you'll be fine!

    It also said that the rear of the chip is metal and connected internally, so you need to take precautions. However depending on what the heatsink is connected to, then it may have been designed to be non insulated, as that part of the chip appeared to be grounded. But just be aware of the options here!

  7. #7
    Thanks GND, i have ordered the untinned one and will try that. I will look at the other other chips for guidance on how its connected to the heatsink.

  8. #8
    GND's Avatar
    Lives in Cambridge, United Kingdom. Last Activity: 1 Week Ago Has been a member for 2-3 years. Has a total post count of 55. Received thanks 1 times, giving thanks to others 9 times.
    Sounds like a plan! Let us know how it goes....

    Cheers
    Graeme

  9. #9
    either the TA8435HQ stepper driver IC needs to be electricaly isolated from the heatsink or the heatsink needs to be grounded
    otherwise a faulty IC will damage other ICs mounted on the same heatsink !

    take a close look at the discoloured contacts
    Click image for larger version. 

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    check the socket for heat damage that may of softened the spring contact
    so it will no longer grip the new IC's pins as tight as it should


    John

  10. #10
    GND's Avatar
    Lives in Cambridge, United Kingdom. Last Activity: 1 Week Ago Has been a member for 2-3 years. Has a total post count of 55. Received thanks 1 times, giving thanks to others 9 times.
    Good clarification, John - I assumed as much but I was in a bit of a rush and didn't explain myself very well last night! The back of the chip is internally connected to ground, so if the designer of the equipment didn't insulate it from the common heatsink, then the heatsink must be grounded as you say. I'd argue it's not ideal practice, and that insulating the chips individually is perhaps preferable. But best just reproduce what the manufacturer did, as it seems to work. Unless that was the cause of the failure of course....!

    Well spotted regarding the contacts - they do look a bit iffy! Those are "turned pin" type sockets - high quality ones, which is a good start. But definitely worth following John's suggestion to check them carefully, or even replace them. That of course involves soldering :-)

    Graeme

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