REALLY need help to ID caps and find replacement!

[fastline]

My Monday SUCKED! We have critical parts to make and our spindle drive on a CNC went down, leaving me gray hairs...

I repaired this drive last month and found corrosion under a cap on the power supply board that was causing a short. Yesterday it failed the same way and I found a cap that was leaking out but testing decent. ESR was .25. I replaced the cap with a standard I had which was .20 but I am thinking of replacing every cap on the board and cleaning under them for starters. I am not sure if ultra low ESR caps are required or what. Just hoping installing high end caps will get the job done.

Anyway, all of them are Nichicon PL(M). I cannot find a spec for them to determine if they are considered just low ESR, or ultra low ESR. Can anyone help?

 

[fastline]

OK, I did find a cross reference for my PL series caps which are indeed extremely low ESR. However, the ESR I am testing in circuit looks to be spot. I thought .25 was high but the new OEM spec is .24.

 

[Sceadwian]

Replacing components in this way will quickly lead you to chasing ghosts as other components blow in the wake of the theoretically bad caps.

No doubt what you've found so far indicts the caps, but it's not a smoking gun, perhaps the leaking/aging caps have caused a drive transistor to overheat over a longer period of time and it's exhibiting electromigration, and the cap failure was just the first critical failure observed not the actual cause of it.

Can you test the ESR on every cap in the unit (of comparable capacity/voltage) ? That should give you a baseline unless all of the caps are failing simply from age, which will require known components values from the original schematic to replace with an exact (or close enough) match.

Can you shed some more light on the machines history/age? Corrosion leakage and capacitors in the same sentence strongly suggest there is nothing new about this machine.

I work at a machine ship that almost always has at least one CNC machine down from a board failure because they keep trying to slap bandaids on aged obsolete equipment.

 

[fastline]

Sorry, machine and drive are about 15yo and I doubt the drive has been serviced in that long. Since posting, I found a shorted cap on another board with exactly the same situation. Cap shows short, remove cap and tests fine but found evidence of corrosion and shorting on the traces under the cap. The cap stinks like it is toast. I have ordered 21 capacitors to replace every electrolytic on the boards. After replacing the shorted cap above, the drive fired right up without issue but the cap I used was old. I obtained the OEM specs for the caps in the boards and ordered only ones with higher ripple ratings than what was in it. In talking with a repair shop, this seems a VERY common "update" to replace the electrolytics. No bulging and ESR is testing OK but looks like corrosion developing under the caps is causing issues.

Machine also has about 12K hours on it so safe to say the caps do to plus idle time so probably closer to 20K hours.

 

[Sceadwian]

Replace em all, but make sure you get a good ESR insert, as I stated previously the caps aren't the only thing that have aged 15 years.... Nothing in this machine is to spec anymore.

 

[KeepItSimpleStupid]

I did the same for a bunch of switching power supplies and pretty much that cured nearly all of the issues. It's wierd when They all start failing at the same time.

I had another instrument that failed regularly. In hindsight, I should have upped the temperature ratings. It was always the -15 V supply ripple that gave things away. The instrument was very sensitive to that.