Kind of a generic electrolytic cap question

etpm · 2019-11-14T20:20:44+00:00

One of my CNC machines has a circuit board that has failed 3 times now. The control is a FANUC 3T. It is an older control so failing boards don't surprise me. But it is just the one board. This board has many custom hybrid ICs, some other of the shelf ones, 6 EPROMs, and one electrolytic capacitor. I have checked this cap on two boards with my meter and the cap has the stated value and is not shorted. But I don't have a way to check ESR. The failure mode for all the boards is the same. First the turret on this lathe will occasionally index in the wrong direction. After the machine is powered up for a while it will then start to index properly. I can control the turret rotation from a program but when the board starts to fail it will only index in one direction. Furthermore, then turret should always rotate in the direction that is the shortest to the next tool called up, but when the board starts going bad the turret still only indexes in one direction. Unfortunately this is the wrong direction. After this failure other things start going wrong, like the speed control. Changing the boards has always fixed the problem. Note that when I change the boards I have to swap all the EPROMs so that the programming for the machine operation will be the same. Since all the boards seem to fail the same way I was wondering if somehow a failing cap could cause this failure. Even though the cap value reads fine with my VOM, that does not measure ESR. In any case I'm gonna order some caps and see if anything changes but I would like to know if it is probably gonna be a waste of time. Thanks, Eric

Nov 14, 2019 61 Replies

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Cursitor Doom 6 years ago

Just plain aping. I find it impossible to believe that anyone could

*genuinely* be that stupid. Hence my deduction he's a troll - and now one of the very few posters I've felt it necessary to perma-plonk. Just think of all that valuable future time I've saved myself by avoiding further futile and infantile exchanges from him. >:-}

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Fox's Mercantile 6 years ago

I guess you lied about kill filing me.

"I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

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