110 alarm A SDU 1

[rotec]

Slowing getting this machine working after 10 years !
I'm getting close.

I have an SDU alarm. Drive unit shows no LEDS.
I tried a second SDU from another machine. Same alarm and still no LEDS
any ideas ?

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[Factory Guy]

It's hard to troubleshoot without knowing which drive you have. Check the obvious, incoming power on R,S,T, inputs and check for blown fuses. What machine, control and SDU drive?

[rotec]

Hi Factory guy, its an Okuma LB15 with a fanuc SDU

[rotec]

Ok I did find a blown fuse, its was one of the small glass fuses on behind the main board. The one marked S in this pic.
Any ideas where the short might be?

Also with both fuses removed. the top two wires have continuity across each other, Not sure if they should?

[Factory Guy]

The attachment below will help you troubleshoot your problems better than I can explain. See section #4.

[rotec]

Thanks, I can confirm that the glass 5amp fuses (2 off) on the rear section top left corner behind the circuit board, keep blowing. When I remove the 6 x output wires on the T1 tremnal block the short goes away and the SDU comes alive, machine moves with no alarms but obviously no spindle.

I'd like to confirm I have hooked up the wires correctly on T1. I'd say I have as the original drive had the same fault. So the issue must be some place down stream on the output side.

More investigations. But feel Im getting closer.

[rotec]

After I discovered the two small 5amp fuses blown with the advice given here I did indeed find the fault at the spindle cooling fan which had seized solid and was fried.
So with the motor removed I took off the fan and disconnected it for now.

The then proceeded to remove the back cover and of the motor and expose the pulse generator "thingy" on the rear of the shaft. It was spotless in there! Anyway, I reset the gap using some thin paper.

While the motor was out I connected the wires and tried to run it on the ground just to the side of the machine. First few times it was jerking and making noises just like before. I rechecked the plugs on the Fanuc drive and when I can back the spindle worked perfectly! I put it back in the machine and ran some parts, no issue.

Then the next day, cold I noticed it jerking again, so I let it warm up, then once warm it ran fine. That was a few weeks ago.

Today it ran for a few minutes smoothly than while spinning smoothly warming up at say 500 rpm its started making short jolts, got worse and now I'm back to where I started. with the Alarm A SDU 110.

Any ideas before I call Fanuc in?

[rotec]

Further update,
I had a spare VAC circuit board from another Lb15. So I replaced the board only and immediately she worked. Then after a short while I got an alarm, this time a different one, LEDs 2 and 4 lit which in the fanuc alarm book indicate a DC over current. I restarted the machine and ran parts all day.
I don’t consider myself out of the woods but she’s running for now.

[eplus]

Hello, has anybody successfully replaced that vintage Fanuc drive with contemporary inverter? Thank Factory Guy for your pdf, very useful. I have one power transistor shorted, fault 12 and I am afraid repair will be difficult. No info about communication between control unit and drive - to simulate behaviournof original drive.
Many thanks for any helpful ideas, best rgds.

[Algirdas]

repair will be difficult.

Maybe for the first time only. Call somebody who is playing with electronics. This job doesn't requires any soldering. There are many suppliers of power transistors on the internet, just choose what is the best for you.