Cebora pocket turbo 130 - no arc and no wire feed

[Dovydas]

Hello,

I have Cebora pocket turbo 130 mig welder, and it suddenly stopped working. Few days ago it worked fine, and today, when I tried to weld, there was no wire feed and no arc. I can hear the transformator working, the fan is spinning, power control buttons are working, I can control the power, but nothing happens when I press the trigger, there is no wire feed, no arc. Things I checked:
1. Tested the trigger itself, checked the continuity with multimeter, it is working.
2. Checked the voltage at the contactor - there is 0 V, I guess that's the problem.
Maybe someone knows what I should do about it, what could be wrong, what else I should check. Wires going to the contactor seem to be fine.

 

[RonA]

It’ll be your contractor. Repaired my mates turbo 130 a few years ago by replacing the contractor. They are a fairly common type you should be able to source from any industrial electrical suppliers, may even get one on ebay
RonA

 

[gaz1]

you could be looking for something like this inside your machine on a pcb board

https://uk.rs-online.com/web/p/prod...VybTtCh1v4gB9EAQYESABEgKk8fD_BwE&gclsrc=aw.ds

 

[eddie49]

According to the schematic, the Cebora is one of those MIGs where the Contactor is on the secondary side of the transformer ( with the contacts paralleled-up to share the high current ):

https://www.mig-welding.co.uk/forum/threads/cebora-pocket-turbo-130.67586/

2. Checked the voltage at the contactor - there is 0 V, I guess that's the problem.

Do you mean there is 0v at the input contact of the Contactor, or 0v across the coil when you press the trigger?
I believe that there is a small relay on the PCB which should feed 230v to the coil of large Contactor.
The Contactor itself probably has a black button in the centre of the top surface - you can push this button in manually to check if you get an arc at the torch tip.

 

[eddie49]

On second thoughts, since you have also lost wirefeed as well as arc, you need to check if there is basically anything coming out of the transformer secondary. Depending on setting of the power control buttons, there should be 15 to 30v AC out of the thick secondary wires, and about the same DC across the + and - output of the rectifier.

 

[Dovydas]

According to the schematic, the Cebora is one of those MIGs where the Contactor is on the secondary side of the transformer ( with the contacts paralleled-up to share the high current ):

https://www.mig-welding.co.uk/forum/threads/cebora-pocket-turbo-130.67586/



Do you mean there is 0v at the input contact of the Contactor, or 0v across the coil when you press the trigger?
I believe that there is a small relay on the PCB which should feed 230v to the coil of large Contactor.
The Contactor itself probably has a black button in the centre of the top surface - you can push this button in manually to check if you get an arc at the torch tip.

There is 0 V across the wires of contactor coil when I press the trigger. Yes, there is a small relay on the PCB of wire speed control, the same relay as in the photo, which was posted by gaz1, I wonder which contacts of the relay I should check to measure if there is 230V or not.
I will try to push the contactor center button and check if I get an arc or not and post the results tomorrow.
I will try to measure the transformer secondary voltage too.
Thanks for your help.

 

[gaz1]

when you pull the trigger it should click if no click then theyve welded to each other
or theres no power supply to it

 

[Dovydas]

when you pull the trigger it should click if no click then theyve welded to each other
or theres no power supply to it

There is no click, I should check the power supply, at first sight that relay looked okay. When I pull the trigger nothing happens.

 

[Sean]

Check the simplest first . There are some spring contacts behind the trigger in the torch, it has a couple of hardened contacts like old ignition points. Constant stop start burns them and they become high resistance. Open the torch and polish the faces with some emery paper. Mine did it all the time, stuck a SIP torch on to my friends Snap On in his garage as it did the same.

 

[Dovydas]

Check the simplest first . There are some spring contacts behind the trigger in the torch, it has a couple of hardened contacts like old ignition points. Constant stop start burns them and they become high resistance. Open the torch and polish the faces with some emery paper. Mine did it all the time, stuck a SIP torch on to my friends Snap On in his garage as it did the same.

Thanks for a tip, I did that before measuring voltages and so on, but it didn't help.

 

[eddie49]

Post number 7 of the previous Forum thread that I linked to above has the circuit diagram ( www.cebora.it/sche/sche886.pdf ).
This shows that connector pins B2 and B3 on the control board will be bridged by the small relay, if it operates, to complete the supply of 230v AC power to the operating coil of the Contactor. To get that small relay to click, and to get the wirefeed motor to run, you need DC power on pins A2 ( + ) and A3 ( - ). The positive signal from the torch trigger comes in on pin A1. The contacts of the Contactor are in series with the negative welding return lead ( the "Earth" ), after the inductor. All the functionality of the control board depends on the rectified secondary DC voltage - about 15 to 30 v DC.

 

[Dovydas]

Post number 7 of the previous Forum thread that I linked to above has the circuit diagram ( www.cebora.it/sche/sche886.pdf ).
This shows that connector pins B2 and B3 on the control board will be bridged by the small relay, if it operates, to complete the supply of 230v AC power to the operating coil of the Contactor. To get that small relay to click, and to get the wirefeed motor to run, you need DC power on pins A2 ( + ) and A3 ( - ). The positive signal from the torch trigger comes in on pin A1. The contacts of the Contactor are in series with the negative welding return lead ( the "Earth" ), after the inductor. All the functionality of the control board depends on the rectified secondary DC voltage - about 15 to 30 v DC.

Thank you for this clear explanation, now I can clearly understand how it works.
So I have measured the transformer primary and secondary voltages today, at the maximum setting the primary voltage is 32,6 V, and the secondary voltage is 4,6 V at the thick wires, which go to the rectifier. Why is that so low, what could be the cause?

 

[eddie49]

If the primary voltage is only 32v AC, it means you have lost mains power somewhere on the input circuit. It should be 230v AC !
Disconnect the machine from the power socket and check all the connections at the power on/off switch, the thermal cut-out, and the power range selector switches ( MIN/MAX and 1/2 ). Look for loose or burnt connections, and check for continuity through these components with an Ohmmeter.

 

[Dovydas]

I think I was just measuring the voltage at the wrong wires that time, there is 230 V AC coming to the transformer, and I can get an arc if I push the button in the center of contactor, but no wire feed.
There was some kind of modification done to this mig by previous owner, maybe that is causing all this trouble, because it is associated with wire feed wires, I want to bypass it, but my mig circuit board is little bit different from the one which is in the circuit diagram you posted. It has 7 pins instead of 3, so now I trying to find a circuit diagram which is similar to my one.

 

[eddie49]

It's good that you are able to get an arc with the Contactor closed manually. That means the main welding power circuit is OK.
Yes, this welder has been modified...! As well as a different control PCB, it has an auxiliary power supply, and two large capacitors - probably to smooth the welding current. These components have been added into the wire spool space.
The new alternative PCB looks to be in good condition. I would start by investigating the auxiliary power supply. There is a medium-size transformer next to a board with four weird-looking components that could well be diodes. So check for 230v AC mains into that transformer, then maybe 12v or 20v AC out, and DC after the rectifiers. If that is all OK, then trace the wiring from there over to the new control PCB.
However, that board also has a square black component - it could be a relay, or yet another transformer ?

( If those two large capacitors are across the welding power, I think the wires should be thicker... )