Lincoln 350c tripping circuit breaker

[mike 109444]

It does not look like there are any relays on the pcb so would suspect one of the four transistors at the bottom of the pcb ( the three legged devices) one may be shorted. If you have a meter it might be possible to compare each device by metering the three pins to see if there is one showing different than others.(assuming they are all the same, check any number on them).
If you switch welder on and it operates the contactor (you call the main switch/relay) if when you then pull the trigger does the wire THEN feed? and or GAS valve operate?
The reason disconnecting the wire from the rectifier stop it is because you have removed the low voltage supply to the pcb. Same I would suspect for the plug that you remove.
If you look at the contactor there will be two thin wires (rather than the thick wires on it) going to/from it, probable connected on it to something like A1 and A2.
This pair of wires should be the ones that feed a low voltage to the contactor to make it operate. You should follow these wires back to the pcb. Then that will show you where on the plugs it is getting it's feed from. Then you will have to see what connects on the pcb to that pair of wires. Then post a GOOD pic of the pcb indicating the wire pair.

 

[mike 109444]

The white arrow MAY point to one of the two wires

 

[mike 109444]

This was the ori contactor in my mig (replaced now) NOTE this is a 240v single phase so not as many wires as yours!
The white wires are the one that OPERATE the contactor and switch it on.
As you can see they and there connections are separate from the other wires.

 

[jimsbeast]

Thanks for your advice sounds like its definatly the pcb somewhere then, ive found the wires going to the large contactor which operate it, unfortunatly the pcb is sealed up with a plastic/rubbery cover which i might not be able to get through but will try. I will also try and call lincoln too. When i turn the welder on the main contator operated but when i pull the trigger nothing happens at all no wire feed. But if i pull the wire out by hand once ive turned the welder on i can weld without pulling the trigger thanks again for your help i will try and snap some more photos this weekend

 

[mike 109444]

It should be possible with a pair of meter probes sharpened to a point to pierce through the coating to get a reading (it's when they pot it in a hard resin that it's a pain)
If you are taking the pic with a digital camera or phone camera see if it has a macro function as this is better for close up photos

 

[jimsbeast]

Hi all juat an update on my lincoln 350c pro problems, today i recieved a new pc board but i still have the same problem, although now the welder starts fine and makes all the noiaes you would expect it too nothing happens... I have checked the torch and shorted the contact ive been in touch wih whoever i can, lincoln and other welding suppliers some who have suggested the aux transer which supplies power to the pc board, i realise that if i was more competent with electrial testing i would be doing better than i am at the moment, just thought i would put another message up to see if you guys have any advise on where to look next on my welder and how i can test the aux transformer. Thanks again for your help and advice. James

 

[mike 109444]

The AUX transformer is the small transformer (looks about 6" square) just behind the yellow three terminal choc block where the L3,L2,L1 go in.
There is a thin blue wire (and possible black) on left side that looks to feed 24v ac? to the fan. It will have an input to it! (maybe 240V from one of the 3 phases). It may also have other outputs for the low AC voltage going to the bridge in the pcb box. You should find on the bridge there are two AC input terminals marked with "~" and a terminal marked "+" and one marked "-". If you meter the inputs you should have between 24 to 30 vAC. Then on the +&- outputs you should see a similar DC voltage. Unless these voltages are very much higher or LOWER then that part of the AUX transformer is ok. It does look like there are some other outputs towards the rear of the AUX but can't see clearly from the pics. You may need to unbolt the AUX to see properly. Take care when working on the machine with power applied !!!!

 

[jimsbeast]

Hi mike thanks for your quick response, really helpful, ive got this wiring diagram too which can help and ive located all the wires of the transformer including those going to the bridge pc board Hope u can see from the wiring diagram I have taken readings off every wire and they are as follows. Bottom left (~42v yellow) showing 1v. Next along (~24v) cant find this on transformer. Next along (grey) showing 1v. But also interesting on the top (input side) see the 3 inputs ( 4,5. 230v and 400v). When i take a reading from them they show 230v, 230v and 110v (not 400). Not sure if this is significant or not. Thanks again. James

 

[mike 109444]

I think to get those reading you are not connecting your meter correctly.
To start you would measure the input of the transformer which is the connections on the longer of the thick black lines (4,5,2,6,3) As the machine is 3 phase there is the facility to input to the transformer 240vAC OR 400vAC. That is why X12 has that curved line in the box indicating it is a link/jumper wire. I would assume from some of your readings that it is jumpered/linked for 240vAC INPUT. So metering BETWEEN pins/spade connectors 4 and 2 you should get 240vAC. Don't think the pin 3 input would need to be used but if you wanted to meter it you would meter between pin/spade 4 and pin/spade 3.
Then to check the OUTPUT of the transformer you would meter between pin 11 and pin 12 this should give 42vAC. This is then fed into the bridge rectifier V2 that is mounted in the pcb box. That turns it into DC (NOW SET YOUR METER ON DC!!) which is then fed onto the pcb plug/connections J1-2 and J3-2. The designations J1 and J3 will refer to the black plugs that plug into the pcb and the -2 and -2 refer to the pins on those plugs (there is usually tiny numbers on the plugs to indicate which is which!) You could just follow the wires from the bridge. If after all the above you get to the pcb plugs and find the DC voltage points, try while meter the DC voltage pull the trigger and see if the DC voltages drops by a large amount. Let us know the result.
I am not sure from what I can see if the voltages from the transformer will be there all the time or only when the trigger is pressed. I would assume all the time as it is feeding the DC power that the pcb needs to operate.
Note also that the 42vAC also goes off to other parts of the welder X2/9 and somewhere else.
All the above will confirm that the AUX transformer is working if the DC voltage does not drop by much when trigger pulled.

 

[jimsbeast]

Hi mike thanks again and apologies for my limited electrical knowledge im not sure if my tester is the right for this job but does have ac/dc sides, the readings i get are as follows, between number 2 and 4 on the imput i get 230 like u said. On the output im getting 40 which is good i guess and chanding to dc at the pc board im getting 55 and when i pull the trigger it does nothing at all to this. Thanks as always. James

 

[mike 109444]

Your meter seams so far suitable.
The voltages you have metered so far look correct.
Can you locate the K1 and even the K2 relays ? The K1 should be operating the wire feed motor and the K2 gas relay.
Can you post up the complete diagram?

 

[jimsbeast]

Hi mike heres a wiring diagram

http://servicenavigator.lincolnelectric.eu/files/docs/469.pdf

Also im pretty sure my welder is set up for 400v as the jumper wire is set like that, if that makes any difference

 

[mike 109444]

I think this model has it, so does the wire "inch forward" button feed any wire ?
What was the source of the replacement pcb ?
Is there a second pcb (behind the display) and maybe a third with the wire feed control fixed to it ?
Looking at the diagram it seams to indicate these additional pcb's

 

[jimsbeast]

hi mike yes there is another pc board which has the amps/wirespeed display on it, i wonder if i can test this board at all? The digital displays seem to work ok, showing wirespeed and adjusting with the dial, i believe these digital displays can show up errors but they arent at the moment Thanks again james

 

[mike 109444]

Reading back through the posts Your original fault was that the contactor (big white thing!) was pulling in as soon as you powered the machine on though if you pulled wire through it would weld (operate arc) if trigger pulled. Now having replaced pcb the contactor is not pulling in on power up and does what it should namely pulls in when trigger pulled but still no wire feed. So it is now just not operating the wire feed. Is it though operating the gas valve ? Have you been able to find the K1 and K2 relays? Note they also designate the contactor as a K1 ! If you follow the wires from the pcb plug J1 pin7 (Black wire) and J3 pin 1 (orange wire) the should go to two relays.
Something else to meter is the wires from the pcb to the wire feed motor M2 Set your meter to Ohms (low setting, say 200) and with power off) put one meter probe on pcb plug J1 pin 5 (red wire) and other probe on the red wire at the wire feed motor. You should see on meter 00.00 or very close to this. Now do same for J1 pin 12 (blue wire) and other probe on the black wire on feed motor. again you should see 00.00.
Have you checked ALL the controls are at there Normal settings ?
There is indicated a resettable trip on back of machine for the protection of water cooler when fitted. This could also interrupt machine even if the water cooler is not used.
Have been looking through the manual for machine and noticed the mention of cooler.

 

[jimsbeast]

Hi mike, i will do all the tests you suggest and also look for the k1 and k2 relays, Just to confirm when i pull the trigger the main power contactor does not come in at all.(although my initial problem was that this would operate as soon as i swtuched the machine on) like u said. Also i will look for the water cooler trip, not sure where this trip might be how does ot look on the wiring diagram? My machine doesnt have a water cooler, but i believe some did, bigger models maybe. All the controls are normal and i have tried to operate the welder on all the different settings.
As the trigger operates nothing at all thats why i havent gone down the route of testing individual gas valve, wire feed etc cos i felt it must be something before power gets to these. Thanks again for all your help will let you know how i get on. James

 

[mike 109444]

I assumed you had the operators manual (if not see attached pdf doc). If you look at page A4 and the item 22 is a trip on rear of machine.
If you can trace the two thin wires coming from the contactor and going to the pcb, they should connect to one of the plugs. If you now set meter to AC volts and measure to see what voltage you get. Expect to see 30 to 60 v
I think the two items shown on the diagram as K1 are both part of the one device (the contactor) hence the blue dashed lines

 

[jimsbeast]

Hi mike, ive done some digging and have made a little progress the two wires from the main contactor are black and red i have traced them back and black goes to J1 7 as you can see from the wiring diagram the other wire (red) goes to i think.... The bridge rectifier Then i saw this (see photo) i had to take the wires off the bridge rectifier to change the pc board and the red wire wasnt replaced, when i look at the wiring diagram of the bridge rectifier there are 4 wires, all there but no red wire, there is an orange wire which goes from the pcb to K2 which i think is the gas valve, this is supposed to connect to white wire on bridge rectifier but i cant see where on my welder Maybe you could shed some light on this and check i have the rectifier wires on correctly (i did draw them before removing them then refitted but i dont know where the red wire is supposed to go, it comes from the main contactor. Thanks again. James

 

[mike 109444]

The red goes on with the white (see pic. There is a double connector / piggy back connector on the white for it) the diagram does show the orange as connecting the pcb to the K2 relay but does not indicate that it is still orange when it comes out of the K2 and goes to the bridge. That was my assumption hence why I coloured it orange! With the red not connected you would have NO operation of the contactor much as the current fault is !!! I did see the wire off in your earlier posts but assumed that was when you were trying to isolate the fault and had put it back.
Hoping now that when reconnected you will have the contactor working and all will be well

 

[jimsbeast]

Hi mike ive connected the red wire up and also checked out the wiring from the pcb to the main contactor and it all tallys up with the wiring diagram k1 is the main contactor and k2 is the gas valve Still nothing!!! I have tested the pcb output to the contactor and theres nothing there. could this be a fault with the bridge rectifier? I dont get any reading from the wires which go to the torch either not sure if there should be Im not sure where i should test next im not certain any power is even getting to the pcb board or where that comes from if you could advise me on what to test next would be much appreciated im determined to find this problem not least because of how much the welder cost and also the fact that i need to weld! Thanks for your help
James