15XT AMC Spindle drive bad capacitors

Have you seen anything like this before? 2004 VMC-15 XT with 7500rpm spindle.

The drive was still barely working but lacking power and smoothness. Especially deacceleration sounded very strange. Bus voltage was fine at 325VDC, transformer was tapped correctly. The machine had something like 30k power on hours.

Attachment 460532 Attachment 460538 Attachment 460540

Attachment 460542
Drive after cleaning and recapping, back together and ready to to work once again. I did replace plastic caps and inrush limiters even though they were still in ok condition. Every single electrolytic measured super bad, even ones that were not bulging. Best one measured about 140µF and ESR of well over 10 ohms.



Original electrolytics were Illinois Capacitor LBAM 450 V 470 µF part# 477LBA450M2EH

0.529 Ohms ESR 2.5 Amps ripple current rating


I replaced them (all 13 pieces) successfully with Kemet ALC70 450 V 470 µF part# ALC70A471DF450

0.299 Ohms ESR 2.54 Amps ripple current rating


I know the bus capacitor type is not all that critical but i wanted to at least match OEM components from known good manufacturer.

Great job. I think it's one of the few places they used electrolytic caps. They give up the ghost after a long while.
I have some really nice Carver Professional Amps that have way too many caps that will soon die. I dread that day!

Thanks you for sharing!

Quote:

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Originally Posted by Kizmo

Have you seen anything like this before? 2004 VMC-15 XT with 7500rpm spindle.

The drive was still barely working but lacking power and smoothness. Especially deacceleration sounded very strange. Bus voltage was fine at 325VDC, transformer was tapped correctly. The machine had something like 30k power on hours.

Attachment 460532 Attachment 460538 Attachment 460540

Attachment 460542
Drive after cleaning and recapping, back together and ready to to work once again. I did replace plastic caps and inrush limiters even though they were still in ok condition. Every single electrolytic measured super bad, even ones that were not bulging. Best one measured about 140µF and ESR of well over 10 ohms.



Original electrolytics were Illinois Capacitor LBAM 450 V 470 µF part# 477LBA450M2EH

0.529 Ohms ESR 2.5 Amps ripple current rating


I replaced them (all 13 pieces) successfully with Kemet ALC70 450 V 470 µF part# ALC70A471DF450

0.299 Ohms ESR 2.54 Amps ripple current rating


I know the bus capacitor type is not all that critical but i wanted to at least match OEM components from known good manufacturer.

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Thanks for sharing what you had to do to fix the problem. I have the same machine and may come across what your issues were.

That's quite a few Hrs on the unit, but I have seen this in others with about the same run time, also generally a shorter cap life is due to heat and any over-voltage, spikes etc.