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.
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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
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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.
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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
the board in the pic is wk5548 mate, its printed on board out of frame. alright mate, yeah schematic for this no where to be found unfortunately. i did find a replacement board online from the states, they wanted $2.5k aussie dollars, will wait to hear from japan, hopefully they are cheaper.
one last question, have you any idea what r2 is that connects to cn1 by any chnace? i would of thought only 2 wires positive and negative came out the diode block also? thanks mate
CN2 has only two wires from the filter, so that’s probably 240VAC. It’s possible that the filter is also a rectifier, but that’s not indicated in the diagram. CN1 comes from the rectifier, so R2 is a rectified input, but it’s not possible to tell if it’s referenced to P or N. I assume that CN30/31/32 are the DC supplies from the power board. The detect board is powered from the link board (which is itself powered from the power board at CN3) . CT1/2/3/4 (CN7) appear to be part of the power control feedback.
Hi Jordan
R2 seems to come from the junction of a diode and SCR in the block “D1”. To elaborate much further we would have to have the details of “D1” unfortunately.
This diode/SCR combination seem to be connected across the “P” (Phase ??) and “N” (Neutral ??) but as this is portrayed in the block “D1” there may possibly be 3 such networks. I would be only guessing at this stage which could be quite dangerous.
The other thing to think about is my suggestion of a replacement / exchange board. There is always the possibility that there is some other underlying problem on another board which is the core problem. There is no way to tell remotely.
These types of devices are fairly complex and in most cases each section or activity is dependant on all the other blocks. I had some dealings with TIG welders (but not down to this level) some years ago but my activities were confined to the control of. The Gas has to be started in time for ignition where a high voltage of about 5kHz (I think) is superimposed on the welding tip to initiate the arc. If this arc is not started within a predetermined time he whole thing shuts down. After the arc is shut off the gas has to remain for a time to allow the tip to cool without oxidisation. This was a bank of 6 welders used in an automatic process. All PLC controlled.
What I am getting at here is as a DIY project where things can get a bit messy and snowball it could end up being very expensive with a possibility of no result.
With this in mind I would suggest finding a repair facility or an individual with an intimate knowledge of the workings of this device and go from there. This could be more economical in the long term.
Sorry for the bit of gloom. You could get lucky and find what you are looking for here on this Forum but I feel that to diagnose remotely particularly with limited information available would be near impossible. You could even find that any local repair facility might only get to board exchange level as this could be considered the most economical method.
Cheers Bob
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Hi Jordan, Jeff
I just googled “WK5549” and came up with some interesting info.
Firstly that board and “D1” are used in a couple of models. The “200” which is single phase and the “300” which is 3 phase. Now Jordan has not shared the make and model with anyone so it is up in the air which one he has. His post of the interconnect diagram suggests the “300” 3 phase model and suggests he has the maintenance handbook for this.
However the book for the “200” model provides more information. Particularly what goes on inside “D1”.
It appears the mains voltage (single and 3 phase) is directly rectified by D1 (bridge rectifier configuration) and the resultant hi gh voltage unfiltered DC appears across “P” and “N”.
Do not take any notice of the crosses in circles on the connection points I don’t think they mean “Positive” but rather indicate a screw terminal point.
I believe the SCR would be switched to allow this high DC voltage to progress to the IGBT inverter stage.
In the “200” book in section 12 there is some detailed trouble shooting procedures and tests which may be useful.
I think what might be some useful info is exactly what make and model this welder is.
Neither book provided detailed board info but suggests a board swapping method as the recommended repair procedure. OK if you have a shed full of boards I suppose but in this day and age new boards really would be the most economical.
Cheers Bob
This is what seems to be in D1
This would seem to suggest that “P” = Positive (1) and “N” = Negative (2)
Don’t know what “R2” would mean (0) but it would be the rectified high voltage before it was switched by the SCR. Like always available for other power supplies which would make sense.
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Sorry mate, i didnt see your message. It comes straight off the diode block D1 so i assume its DC input? and about the zener, all the other zeners are printed on the board ZD1 ZD2,3,4 etc. There is more of that same diode elsewhere, all marked as regular diode. The zeners also have the zener diode symbal beneath them too. Not sure if that means ruling it out though. Cheers
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Thanks mate, getting a quote from japan as we speak. Ill try track down a repair bloke to have a look. Thanks for help
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The 200 is single phase, 300 is 3 phase. As i said in previous post with pic 3 phase input. And posting 300 manual. I assumed it was known.
Thanks for help, appreciate it mate.
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Hi Jordan
Sorry, I missed that bit. I think there were a few cross over posts earlier.
Refer my post immediately prior. I think I am correct. R2 supplies the unfiltered high voltage DC to Board WK5549 to generate all the other voltages needed for control etc. It looks like the SCR is switched and supplies this high voltage to the IGBT blocks (part of inverter system) when required.
I think I am correct here and not just a guess. But whether this helps you I am not sure.
Google “WK5549” and you will find a link to the 200 model which uses the same D1 and other boards. This manual in section 12 outlines a few more detailed trouble shooting tests and diode block tests which might help you a bit. Although a destroyed diode and some obviously overheated resistors are a pretty sure sign of malfunction. I think “malfunction” might be a bit of an understatement here.
I am off line until next week end so will not see anything but am not ignoring you.
Cheers Bob
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