gday all. first post on here, im wandering if anyone can identify this diodes? i cant find info on them, the one with the wavey line on cathode and 06 marked facing one direction, Then turn it 90° its marked 84 in another direction . The other diode marked with sold stripe on end has 10 85 marked in different directions also. Help appreciated. Cheers
A Wavey line may indicate a Schottky diode.
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Hi Jordan
A bit of a curley one here. They seem to be 2 different varieties of diode as the 2 bands are different, one curley and the other plain. Although having said that it may not be true. Diodes have a habit of changing the markings at the drop of a hat.
Is there any chance of some sort of circuit showing where they are used. That would provide a bit of a clue as to what class they belong. Zener, Schottky, Power, Small signal, Varactor and the list goes on but I think these are the main types in general use but even with this small list you can understand the problem with identification from a couple of pictures.
Could you provide more pictures of each. All with the diode pointing in the same direction and rotated a bit between pics so we can see the exact orientation of the markings. Try to get a bit of more than one number in each shot so we will know which number we are looking at.
Cheers Bob
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Okay mate no worries. I did my best with the new pics. There really small so it isnt easy getting it to focus
Im guessing they are 2 different ones also, they are off a ddc board out of a welder, i know that probably doesnt help, . As to what I dont have a schematic only a wiring diagram which doesnt tell you much. I circled in the pic where the diodes came from in the circuit.
Hi Jordan
You are right. As far as identification is concerned not much help.
There are a couple of tings worth noting.
Firstly how do you know that plug you highlighted (CN1) is RECTIFIED 3 phase mains. If it were rectified I would have expected just positive and negative.
Secondly D1, 2, 3, 4 look suspiciously like a bridge rectifier set up. possibly directly on mains so be careful when playing around. Looks like D4 has failed in a catastrophic manner. Not sure about D5 and D6. ZD1, 2, 3 are zener diodes. Failure of D4 in this manner would suggest a shorted electrolytic cap AFTER the rectifiers, possibly one or both to the right of CN1.
Those resistors at the top left look as if they have been seriously hot. Same for R13 and R14. R12 has a black bit of soot on it which could be the remains of D4.
Looking at the condition of what I think are mails input circuitry components you could have something seriously wrong with this board and i would suggest that if you don’t have the facilities or expertise to effect repair you attempt to get a complete replacement board which should be “plug in”.
There is I think raw mains involved here so if you don’t know or have any doubt DO NOT attempt any type of repair. Dangerous. If not immediately then possibly later.
Depending on exactly what your welder is it might be more economical these days to just get a new one.
Cheers Bob
Hey @jordan284612,
As Bob has said already, working with mains voltage can be and often is deadly. Our advice is always to get a qualified technician to handle repairs like this. The alternative is also to buy a new welder, haha.
That being said, fascinating to analyse these boards.
Hi Zach
May not be as Ha Ha as you think.
Cheers Bob
$6,500 welder mate.
cheers for the advice mate, i say that its 3 phase rectified only because mains 3 phase input passes through filter board, then through Diode block, and out to that board. ill upload wiring diagram if you want to have a look. its shows P N R2 going to CN1, i dont know what R2 is. obviously no expert, but im aware of whats safe and whats not, appreciate your help though. And its a $6500 welder, so would prefer to get it going, speaking to a mob in japan about a possible replacement. cheers
Can you confirm that this is PCB3 - WK-5548.
The label “Control Source” implies that this is 'DC Power" in the block diagram. That makes it possible that at least one of the diodes is a Zener, so it would be dangerous to assume that they are generic power diodes. The parts list does not include any items soldered to a PCB, so that’s no help. If it really is “DC Power” then you know that it needs to produce +/-15VDC +18VDC, +24VDC and +5VDC. There would be a supply input and some sort of control mechanism, but I can’t tell which is which between AC-3 Phase via the filter or rectified unfiltered AC-3-Phase There would also be an error signal from the detect PCB.
A local repair shop that could examine the PCB shuold be able to use similar guesswork, using the block diagram, the circuit diagram and the interconnect list, to come up with suitable replacements.
Hi Jordan.
At $6.5k I can see your point.
I too think this board is PCB3 WK5548 but as Jeff asks this requires confirmation.
The WK-XXXXX should be printed on the board as the other visible one (WK-5549).
To be effective you will need to dig up a circuit for this board. The circuits posted are interconnect diagrams with little detail. It is this detail you need to get down to component level.
Your enquiries from Japan might yield a replacement or change over board. As I said previously looking at the condition of those resistors at top left of pic there could be something seriously wrong here.
Cheers Bob
