So my fanuc robot has a bunch of corroded diodes on its controller boards it that no longer work ive test them on the board which i hope is ok. My question is this. First what kind of diode is this and if you dont know a diodes specs cant you replace it with pretty much any diode in the voltage and current range of the board
That looks like a standard ceramic packaged high current rectifier diode. Typically a 3A, but hard to say from the picture.
The fuse on the board is .32 amp so that should work
If you need a diode quickly, drive on up to Highland Village and I’ll give you a couple 1N4004 diodes.
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Thanks you guys…im only ever able to really make it to makerspace on sundays but ill swap them out then…a great many of the diodes in the system are in similar shape…ive noticed a great deal of corrosion in the cabinet consistent with proximity to salt water i think, im pretty sure the unit spent most of its life in california…i wonder if thats what did it
It apparently went out in a blaze of glory as a heat/smoke emitting diode…
It’s either that or a lot of chlorine was nearby.
There’s a black plastic bin on the floor under the shelves just inside the doorway (to your right as you enter the ELab) that has a variety of diodes. Any chance you can get a part number off the good one?
It’s called a FED - Flame Emitting Diode… 
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Plasma?
I would have liked to see that. But again I have a taste for things blowing up in my face ;-0
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We had some diodes at SSCL that were disks about 3" in diameter by maybe 3/8 thick. They were there to shunt the back EMF from the magnet strings into the dump buses. The buses were 1" or bigger copper pipe parallel to the magnets with 18" vertical standpipes every 50 feet or so. The pipes were filled with water. Which was expected to boil out if there was a quench.
4.6MJ per magnet, 5 magnets per cell. Energy had to go somewhere. Preferably without destroying anything.
Apparently when those big semiconductors go…igbts at least they straight up explode , shrapnel and all, in the datasheet of one of my 1200volt 200 amp igbts it says to design ur enclosure with this in mind…lol
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You can get that effect ( to a smaller extent ) with plain old plastic case power transistors. I vividly remember a chunk of one bouncing off my safety glasses once.
Its actually quite a relief to me because last time i powered up the controller i saw a tuft of smoke come out of the board bank…a real oh shit i fried it moment…but maybe its just these old diodes…i hope at least …i tested it on the board and its got nothing either way so hopefully its sudden absence didnt hurt anything …i can just replace and itll be fine…hopefullyyy
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Unfortunately it is completely un-labelled
A PED?
Reminds me of the white plasma arc that came out of the unhappy brushless motor controller on the first version of the electric go kart. Plasma emitting power fets - PEPFETs. Entertaining stuff.
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Before you power it up again, check and make sure the supply rails are at the right voltage and right polarity. One of the diodes that blew kindof looked like it might have been a reverse polarity protection diode.
Duly noted…the power supply was never removed though plugs straight into the board assembly and the harnesses are seated correctly… some of the boards power up and display power lights and error codes so id imagine if the polarity was reversed nothing would happen or so i hope but ill do so anyway as i dont know the persons who had this before me