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Juki KE750L T/Z Axes problems - Please help!!

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Juki KE750L T/Z Axes problems - Please help!! | 3 September, 2018

Hello everybody,

For a long time the Juki has been not used, but was working fine before that.

Since 4 or 5 month ago, it brings some problems when initializing with T and Z Axes. Till now, just powering it off and on for a few times worked, but not anymore, now is not possible to center all axes, and obviosuly to operate the machine.

Been trying to move heads axes manually and sometimes work some others not, now it doesn't work. Somebody told us that probably defective/old motor drivers, but actually is like 4 or 5 of them failing. When it's not the center head Z, is the left head T, or Right head T axis.. Those motor drivers are not cheap so if we need to change all of them, will be cheaper to buy a new machine.

Can someone point me in a right direction in order to repair this problem? In case is a driver issue, is there any way to repair them like changing mosfets or something like that?

I've tried to find information on internet and on the manual, but no luck. Please, need help on that as soon as possible!!

Thank you! Oriol.


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Juki KE750L T/Z Axes problems - Please help!! | 3 September, 2018

Hi Oriol,

Sounds more like a power supply/low voltage problem if all the driver cards are failing. Can you check if the PSU supplying them is stable?


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Juki KE750L T/Z Axes problems - Please help!! | 5 September, 2018

Hi Rob,

Thanks for your fast response. In fact, after a better look to driver boards, it has leaking SMD Electrolityc caps. Unfortunately after replacing them in 3 units, one of them gives 90% of times, ALARM4 led ON.

Looks like a comunication problem, if I disconnect data cable from one of the drivers, also gives me same alarm. Actually I'm not sure if it's a communication cable but only has two, one to the motor and the other one.

When machine works, it works really great so maybe not a Mosfet related issue.

As you said, can be a power rail failure, I will check power supply but to be honest don't know where exactly it is.

If anyone had same problems, please help!

Best, Oriol.

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Juki KE750L T/Z Axes problems - Please help!! | 30 August, 2019

Hi Rob,

if still have problem chek this:


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Juki KE750L T/Z Axes problems - Please help!! | 1 September, 2019

Have you got a circuit diagram for your driver board? If not measure your driver into a resistive load and look for differences in current flow voltage drops under load dried out caps. Dead current measuring circuits etc. If you see an IC, look it up and you may well find an App note that has the circuit for the output driver in it. Also cn that a motor heck motor leakage black bits near insulation or browning etc. This can be a signthat a motor is about to fail or has failed. Occasionally scraping a little carbon off the insulation will bring a motor back to life. Then coat with a little clear nail varnish.

Anyway Good Luck in your endeavours


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