[smoran22]

Hello, this machine is getting me frustrated.

1984 Matsuura MC 500-v2, 20 tool changer, MX1 Yasnac control.

I keep getting the 333 - Fuse (Z) Blown alarm and red light on servopack board, but if I power off the control and restart a few times it eventually clears and runs just fine.

I tried swapping the servopack circuit board with another board, and the issue was the same. Just got done changing out the entire servopack chassis and the issue still remains. I'm at a loss.

When I check voltage at the "r" and "t" terminals of the CPCR-MR154-K servopack, I have 230V AC. When the machine powers up and runs, I have 360 V DC on the P and N terminals. However the green power light on the servopack circuit board is visibly not as bright as the power light on the X or Y axis boards. I'm suspecting there may be a power issue somewhere since I don't believe that light 'just happens' to be dim on the pack that's giving me trouble, however I'm out of theories as to what to check or where to go next. I'm thinking about giving up and just calling for a tech to come out and look at it.

Anything else I should check before I throw in the towel?

I appreciate your guidance, Thanks!

[freakycnc]

Which of the RED LED's is on?
Brushes may need a good cleaning, also.

Attachment 477056

[smoran22]

The red "FUSE" light is lit on the pack. I have confirmed that the fuse is good. This all happens extremely fast when powering on the control. The SVM contactor closes and immediately opens again.

I'm curious as to why the brushes might have a role in this. I never even considered brushes as a possible explanation, but it's worth a look. Would possibly explain why sometimes the machine powers up right away and sometimes stubbornly refuses... I'll check them as soon as I get a chance.

[smoran22]

I have checked the brushes and can report that they're in great condition. They look almost brand new. No oil or carbon residue, plenty of meat left... Commutator also looks great from what I can see.

[freakycnc]

You can download a book for the MR-K drive from Yaskawa - Downloads.
The manual says "replace the controller unit".
One thing you don't want to do is swap the top boards with other units as you may introduce problems from one amplifier to another.

[smoran22]

Whoops. I had already tried the printed circuit board on the pack because I didn't have an entire pack to test with at first. Later on I had an entire pack to test with. Either PCB on either pack made no difference. Do you think I need to get a rebuilt pack to put in? If there was something wrong with the driver side of the pack that damaged the PCB, I would have likely introduced that into the "good" PCB when I swapped them before. I noticed something in the manual for the servopack that I hadn't checked either. It calls for the incoming mains to the power supply to have one leg connected to the "grounded phase". I'm not sure what it means by that - or how to check it to make sure.

[smoran22]

I think we've gotten everything else sorted out and checked. Based on a previous recommendation from @freakycnc, I want to re-check the brushes and commutator. On initial look, everything looked to be in good shape and very clean. There weren't any grooves or chips or damage that was visible to the naked eye with a good light. However, I'm suspicious that there may be a bad spot on the commutator that I cannot see without rotating the shaft. That leads me to my next question.

How can I rotate the Z axis servo shaft with the brushes removed so I can inspect the entire commutator? I want to make sure that I don't either damage the leadscrew or mess something up with the encoder. Based on my understanding, this machine doesn't have absolute encoders since it needs to be manually homed before each use, so it should be safe to remove the encoder from the top of the servo and manually rotate the shaft... Right? I want to confirm that before I screw something up.

On a related note, what is the recommended method of cleaning the commutator? Is there a specific abrasive, brush, or tool that I should use?

Thanks

[freakycnc]

smoran22,
I would not take the encoder off the motor. There is an access plate on the front of the casting that you can reach the motor coupling and rotate the ballscrew by hand.
If you remove the wires from the Z amplifier you can check whether or not the motor is shorted to ground with an ohm meter with the brushes in and out to see the condition of the motor.
The counterbalance will hold it in place so you can stop and look into the brush holders at the commutator.
Clean, dry air (maybe canned) is best.
Being Z axis the chances of coolant getting in are slim so it should be "clean". Maybe touch up the brush edges with clean scotch brite to remove any arc signs.