Fanuc Output Module Failure

Late Friday afternoon one of our lathes went "boom" .... pretty loudly.
It was an electrical boom to be sure, but there was very little to no magic smoke to be found.

2 banks of units. Bank 1 = basic machine. Bank 2 = Options.
CRT said error on Z, but bank 1 had no alarms at all on the amps.
Bank 2 had an alarm on .... ???? the Power Supply I think....
No alarms @ Control On
Machine would come "up" and then throw the alarms, but stay "up". No movement.

Took out all (7) P/S's and Amps today - expecting to find a big blow hole somewhere.
No signs on first eyeball tour.
Went back through then with the meter, and found one Output Module that shows bad, but it is visually OK. (I ordered replacement(s) )

Checked motor leads with meter (just ohms) and all seems fine there too.


I've replaced a module or two just like this on other machine before, but not sure if I heard them "go" before. (May not have even been in the building at the time)
Does that seem right that it could make "that much" noise, and not let out magic smoke or appear blown? (bulging or ??? like I have seen the snubbers when bad)


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Think Snow Eh!
Ox

IME most "booms" end up being a transistor module in a drive. Can't say I've ever heard the sound of an output module dying. Too small for a "boom" more likely a "pop".

Was the boom from some collateral damage? (Some downstream component is cratered, or the machine did some loud mechanical thing?)

Yea, I would check the components the output card went to for shorts.

Vancbiker said:

IME most "booms" end up being a transistor module in a drive. Can't say I've ever heard the sound of an output module dying. Too small for a "boom" more likely a "pop".

Click to expand...

Yes, I guess they call it a "Transistor Module".

I have replaced them before, just don't recall such drama on the failure.
???

This one was in the Sub Spindle - spindle drive unit. .. and it wasn't even being used on this job.


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Think Snow Eh!
Ox

Ox said:

Yes, I guess they call it a "Transistor Module".

I have replaced them before, just don't recall such drama on the failure.

Click to expand...

It's not uncommon for the drive board to be damaged when a transistor module fails.

Vancbiker said:

It's not uncommon for the drive board to be damaged when a transistor module fails.

Click to expand...

I'm so lucky that this has always been the case for me!

I've had the assosiated "snubber" fail directly after replacing one of these before. Like - the next day?
Not even that long I don't think.
This one checks OK today. We'll see how long it lasts?

Maybe the "snubber" is s'posed to try to save downwind components?
Those snubbers are much rarer find than the modules that they are tied to.
???


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Drainin' the Swamp!
Ox

Well, where is the "egg on face" smiley?


As I was puting everything back together today - except the unit with the ass-u-med bad part on it, I found another drive that had the same readings. I checked all of the similar modules seven ways from Sunday and I was pretty convinced that I diagnosed it wrong.

So my tech was finally able to come over tonight and he dbl checked it, and he thought that it seemed OK too. So we stuffed it all back together and tried to figger it out....

Finally we were back to the main Power Supply unit. We were getting 305V out the top and 24 out the middle, but we just weren't getting a ready signal there, while we WERE getting a ready on the second string Power Supply. So we pulled it out.

Now I had this one out before as well, and I couldn't find any missing smoke in it prior, nor did I smell any loose smoke, but we tore it apart further tonight than I had it earlier.

NOW we found the BOOM!

Two of the three IGBT's blew, and the third is toast.




I've been a party to replacing these before as well, but it's been long enough ago that I forgot to look under the main board.


We originally opened up a few of the P/S and amps a week ago to check into getting new caps to replacing what appears to be an aging one (or more) as I have been getting 401's at power up for some time now (but clear easily) and then I got a Z axis alarm a week'r so ago that I needed to doo a re-boot on to clear, so I expected that I had a dying cap.

We replaced a large cap in a P/S on a similar machine a few yrs ago, and that machine is 3 yrs newer than this one, so I have been expecting to need to replace one in this one any day ever since. However, once we got into these, they are constructed differently, and that one large cap doesn't exist in this machine.


So - I am kind'a hoping that maybe one of these was "pulling down the bus" on start-up, and maybe this will solve the 401 issues. ??? We'll see....


At least now I can see why it went BOOM! The other unit showed no signs of catastrophic failure. At least not enough to provide that much drama...


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Think Snow Eh!
Ox

Conclusion:

So - I ordered up some new IGBT's as shown above off The Bay from what appears to be the biggest source for that - at least on The Bay. An outfit down in Southern Fried Rock territory. (Fla)

I never even tried the Trans Modules that I got in.

I ordered on Thursday morning. Hoping that if they got them out post haste that just maybe I could have them by Sat if they went postal. (no gun involved in this "postal") But it wasn't to bee. Monday comes and goes .... FRIDAY they roll in ....

I have now been down 2 weeks, and most of the time expecting to be back up as soon as parts get here - hopefully tomorrow.


So I stuff the new IGBT's in and shoehorn the amp back in the machine and ............. BOOM!

YEP! YEP YEP! yep, yep, yep ...... (in my best "Al" voice)


So late Friday afternoon I shot an e-mail off to one of the rebuilder's for troubleshooting, expecting to pick up one of their units. Got response back Monday morning, and it was determined to be internal to the unit, but when they sent me a quote I about Shiite. It was 3 large, and usually it seems that 2 channel amps fetch prox half that, so I wasn't quite ready for that. If anything I would have guessed a power supply to be less than an amp, at least a 2 channel amp, not double!


So I called my local teckie guru (not fluent in Fanuc) to see if he wanted to at least look over the upper boards closer - as I am having sticker shock. He wouldn't really be able to get to it for another day, and asked what they go for on The Bay? Turned up that I found several for much less. Boy - I really hated to buy somewhere else, but I went with good used instead for 1/3 the $. In all fairness, I have bought, and will continue to buy many units from this same rebuilder. But I still am about it....


I found a P/S unit that was ending around supper time and was semi local. I ended up with it, and I drove that evening to pick it up from the seller who was actually a Fanuc Tech, and was stripping an "out of service" machine of some sort, and said that this unit was just installed 6 months ago and was rebuilt by Fanuc. So - it seems that I got a screamin' deal. Better than expected?

Next morning I installed and we have been back up and running since. (1 week?)

I am still having the same issues that I thought were related to failing caps as I had previously tho, so this didn't fix that. Need to look into those yet, and soon, but I won't address that in this thread as it's unrelated. (other than via age and hours)


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Think Snow Eh!
Ox