Cebora 883 (Pocket Mig) Wire speed not working.

[bloobloo]

Just tested the SCR again and it's deffo shorted between annode & cathode, open between Annode and cathode to gate.

It's not assembled at the moment to test the trigger wire, however without it connected to the terminal the contatctor doesn't click.

 

[bloobloo]

Do these help?

 

[Neilj]

It's the light grey thing to the left of the relay in that first pic, a bit out of focus in your second pic. Need to try and figure out what that is as I'm trying to work out the circuit diagram from the pics. It seems strange only having 3 wires connected to the pcb, do either of the two motor wires go anywhere else or just to the motor?

 

[Seadog]

That's part of the relay where the contacts are.

 

[bloobloo]

The grey thing is a connector for the wires.

 

[Neilj]

OK, was there was anything connected to it? I've picked up a circuit diagram off the Cebora website:

It says this is the version with contactor but it looks the same as the drawing for the one without contactor so that's not much help. It does show 3 wires to the pcb though; trigger on the right terminal, positive motor feed in the centre and a negative connection on the left terminal. Is that how yours is connected?

 

[bloobloo]

Yes, only 2 wires on the connector at the bottom though, (even though there is space for 3) In fact Im gonna nip to the shed to double check!

 

[bloobloo]

Yep, 2 wires in that connector

 

[eddie49]

@Neilj , the diagram in Post #26 must be for an earlier "Live Torch" version of this Cebora.
Post #10 of this thread:

Cebora Turbo 130 circuit diagram

Hi - got a BOC Migmaster 130 - AKA Cebora Turbo 130 - which I'm in the process of converting to Euro torch after accidentally breaking the original . . . I've fitted the socket and wired it up and everything works so far. The last step is to add a solenoid-operated gas valve. I already have a...

www.mig-welding.co.uk

shows the unusual positioning of the contactor in the welding output circuit, with it's contacts paralleled-up. The contactor apparently has a mains coil, and that diagram does show two wires at the second connector on the PCB.

 

[Neilj]

Thanks @eddie49 , I was thinking earlier this was an ideal time for you to post on here . I'll re-post that diagram here for clarity:

@bloobloo your small grey connector with 2 wires attached feeds the contactor and it makes sense when you say the contactor doesn't click with the pcb removed as the signal for the contactor is fed from the relay contacts on that pcb.
So if we go off this diagram then your 3 wires should go like this; black onto A3, red onto A2 and blue (trigger) onto A1, which I think is what you have now, correct?
Can you measure a couple of voltages and let me know what you get:
A1 (+) to A3 (-), both with the trigger released and pressed.
A2 (+) to A3(-), again both with the trigger released and pressed.

The diagram above shows the motor connected to the positive side of the bridge rectifier (16) but your pics seem to suggest it's wired differently. Having those voltages might help figure it out.

 

[bloobloo]

Thanks @eddie49 , I was thinking earlier this was an ideal time for you to post on here . I'll re-post that diagram here for clarity:
View attachment 385611

@bloobloo your small grey connector with 2 wires attached feeds the contactor and it makes sense when you say the contactor doesn't click with the pcb removed as the signal for the contactor is fed from the relay contacts on that pcb.
So if we go off this diagram then your 3 wires should go like this; black onto A3, red onto A2 and blue (trigger) onto A1, which I think is what you have now, correct?
Can you measure a couple of voltages and let me know what you get:
A1 (+) to A3 (-), both with the trigger released and pressed.
A2 (+) to A3(-), again both with the trigger released and pressed.

The diagram above shows the motor connected to the positive side of the bridge rectifier (16) but your pics seem to suggest it's wired differently. Having those voltages might help figure it out.

Yes, black red blue wiring. However I removed the SCR and am awaiting delivery of the new one so cant test the voltages just yet for you.

 

[Neilj]

You could still test A1 to A3 (trigger released / pressed) and also A2 to A3 with the trigger released if you fancy popping the pcb back in? I'm particularly curious on what you see across A2 and A3 as the pics of your board don't seem to match up with the diagram above.

 

[bloobloo]

You could still test A1 to A3 (trigger released / pressed) and also A2 to A3 with the trigger released if you fancy popping the pcb back in? I'm particularly curious on what you see across A2 and A3 as the pics of your board don't seem to match up with the diagram above.

I will connect it back up tomorrow and post the readings. With any luck Royal snail will have delivered the replacement SCR

 

[bloobloo]

You could still test A1 to A3 (trigger released / pressed) and also A2 to A3 with the trigger released if you fancy popping the pcb back in? I'm particularly curious on what you see across A2 and A3 as the pics of your board don't seem to match up with the diagram above.

Ok
A1-A3 23.5v
A2-A3 23.47v

 

[Neilj]

Ok
A1-A3 23.5v
A2-A3 23.47v

Was A1-A3 with the trigger pressed?

 

[bloobloo]

Was A1-A3 with the trigger pressed?

Sorry, I was in a rush when I replied. All readings are with the trigger pressed, I don't think there was any voltage at all without pressing the trigger.
What I did also notice was the polarity didn't change on the meter when testing, Looking like there is 2 positives going to the motor. Like I say though I was rushing about and should have took more notes / notice

 

[Neilj]

That's what I expected based on the diagram that @eddie49 posted. The motor supply is directly from the bridge rectifier and the wire that goes from the motor to terminal A2 on the board is the negative side of the motor. The board will pull this down to something approaching 0v depending on speed selection. With the SCR removed I'd expect A2 - A3 to give you the full 25v as you found.
Hopefully your new SCR will fix it, post back and let us know either way.

 

[bloobloo]

Little update. The SCR arrived today so I've just been in the workshop and soldered it on. And.... it still didnt spin the feed motor. So took the board back out again, and got the tester out. I found the issue of a broken track between A1 and the annode of the SCR. Ive soldered along the track as a repair so hopefully it will do the job.

It's all back together now and seems to be working. I've not been able to test welding with it yet as I need to cobble together a top roller / tensioner and hopefully move the spigot that holds the wire reel either lower or further back. I don't use the small reels of wire and only have the 5kg to hand, so need to make one of these fit.

 

[bloobloo]

Some more pics of today’s progress. Made a wire feed tensioner from a spare Broken one I had knocking about in the drawer, then made a reel holder and mounted it in a better place to enable the use of 5kg reels. Finally tested it and it works great!