Supermig 185 not working. Help

[Jonny weld]

Trying to find a pin for pin replacement transformer might end up being a real pain. Marini don't list the 2.8VA range, only 2.5VA or 2.3VA. You'll probably get away with using the 2.5VA part. eBay is a right pain, and the transformers there seem quite expensive.

Trasformatori Resinati, Ei30 - Trasformatori Di Sicurezza Con Protezione Da Circuito Stampato, Ei38 -trasformatori Di Sicurezza Da Circuito Stampato, Ei42 -trasformatori Di Sicurezza Da Circuito Stampato, Ei48 -trasformatori Di Sicurezza Da Circuito

www.marini.it

You might be better off getting something like this, screwing it to the case, and running wires from the transformer to the circuit board, after removing the original transformer.

Pardon our interruption...

Or this might fit. The image shows a 9V rated transformer, but the main spec in the listing says 12V output:

https://www.amazon.co.uk/YHDC-transformer-PE2820-I-230V-12V-Blue/dp/B087349TCB

Look like the do it but couldn't find one anywhere

I have ordered the one off Amazon while I see if the original replacement will show up somewhere

 

[voipio]

Yes, the small plastic-encapsulated PCB-mounted transformers seem to be quite fragile and they do fail quite often. Usually it is the primary that goes open-circuit, since it is running as long as the welder is powered on.
The small transformer only supplies the relay or contactor which enables the main welding transformer. That relay will also often power the gas valve, and the wirefeed motor is supplied with variable DC power from the output of the main welding transformer, via the speed control circuit on the PCB. So if the 12v transformer is not working, the relay will not operate, and nothing will work.
Rather than a contactor, this welder has a large-ish relay mounted on the PCB - the black plastic block below the small transformer.
The normally-open contacts of that relay are the two tags on the top. You could short or switch-on the two wires that have push-on tags. The welder should then burst into life....

The contactor shown in the wiring diagram has four contacts, two sharing the live, and two sharing the neutral to the main transformer. so should have eight terminals. The relay with two terminals is probably for the solenoid valve.

 

[Jonny weld]

The contactor shown in the wiring diagram has four contacts, two sharing the live, and two sharing the neutral to the main transformer. so should have eight terminals. The relay with two terminals is probably for the solenoid valve.

I have ordered the Amazon part you suggested. Shall I be able to replace like for like?

Thanks for sorry for being a pain

 

[voipio]

The second image in the Amazon listing gives the dimensions of the case, and also the pin connection spacings. The listing shows the transformer to have a single 12V secondary (not 2 x 12V), so the pins used for the output will be 7 and 9 (10.16mm apart). The input pins are shown as 20.32mm apart, and the pin grid spacing between input and output pins is 20.32mm. The case is shown as 28 x 32mm max.

 

[Jonny weld]

The second image in the Amazon listing gives the dimensions of the case, and also the pin connection spacings. The listing shows the transformer to have a single 12V secondary (not 2 x 12V), so the pins used for the output will be 7 and 9 (10.16mm apart). The input pins are shown as 20.32mm apart, and the pin grid spacing between input and output pins is 20.32mm. The case is shown as 28 x 32mm max.

Not an electronic. You reckon it will work or need to cancel order?

 

[voipio]

The transformer in the Amazon listing is given as 230V AC primary, and single12V AC secondary, rated at 3VA, so basically the same as the original, so it should work as a replacement for the existing transformer. If they send something that is different to that, then return it as "not as described". Looking at your image of the back side of the wire feed control board, the mains input pins to the primary of the existing transformer are twice as far apart as the secondary pins, which is the same as in the Amazon listing.

Have you measured the length and width of the existing transformer case? Will the new one fit into the same space? The height of the transformer off the board doesn't matter, since there is nothing in the way, heightwise.

 

[eddie49]

The contactor shown in the wiring diagram has four contacts, two sharing the live, and two sharing the neutral to the main transformer. so should have eight terminals. The relay with two terminals is probably for the solenoid valve.

I think the wiring diagram is for a different version. It shows an off-board auxiliary transformer, and a gas valve in parallel with the contactor coil.
There is no contactor visible in the internal photo of this model. The large black plastic block relay on the PCB probably has contacts rated at 20 Amps, capable of handling the main transformer.

Just want make sure nothing else is broken

Did you try my suggestion in Post #20 of connecting together the two wires that plug into the top of the relay?

 

[Jonny weld]

I think the wiring diagram is for a different version. It shows an off-board auxiliary transformer, and a gas valve in parallel with the contactor coil.
There is no contactor visible in the internal photo of this model. The large black plastic block relay on the PCB probably has contacts rated at 20 Amps, capable of handling the main transformer.


Did you try my suggestion in Post #20 of connecting together the two wires that plug into the top of the relay?

Not yet. Let me better understand. as per photo you mean to remove those 2 connector and join together with tape?

Thanks

 

[eddie49]

Yes, those two wires removed from the tags on the relay - black plastic block - and joined together should run the whole welder, as soon as you power it on.

It may be better to do this in a more controlled 2-step way:
Power off and unplug the power cord. Pull the two wires off the relay. It is just an on/off switch, so no need to mark which wire went to which tag. Find a mains-capable insulated on/off switch - e.g. a good-quality wall light switch. Join the two wires that were on the relay to the terminals of the switch. Plug the welder in, and switch it on using the On/Off switch on the front panel of the welder. Then operate the test switch which you have added. It should simulate pressing and holding the trigger on the MIG torch, so the gas valve, the wirefeed motor, and the arc at the tip of the MIG wire should all be enabled as long as that new switch is closed.

If this is all working, it proves that the only fault is the missing 12 volts from the small transformer, that would normally be closing the relay. Unplug, remove the test switch, and plug the two wires back onto the relay. After fitting the new 12v transformer, hopefully the welder will be fully operational.

 

[Jonny weld]

Yes, those two wires removed from the tags on the relay - black plastic block - and joined together should run the whole welder, as soon as you power it on.

It may be better to do this in a more controlled 2-step way:
Power off and unplug the power cord. Pull the two wires off the relay. It is just an on/off switch, so no need to mark which wire went to which tag. Find a mains-capable insulated on/off switch - e.g. a good-quality wall light switch. Join the two wires that were on the relay to the terminals of the switch. Plug the welder in, and switch it on using the On/Off switch on the front panel of the welder. Then operate the test switch which you have added. It should simulate pressing and holding the trigger on the MIG torch, so the gas valve, the wirefeed motor, and the arc at the tip of the MIG wire should all be enabled as long as that new switch is closed.

If this is all working, it proves that the only fault is the missing 12 volts from the small transformer, that would normally be closing the relay. Unplug, remove the test switch, and plug the two wires back onto the relay. After fitting the new 12v transformer, hopefully the welder will be fully operational.

Sorry for the delay.

I did try to connect the wire from the relay with a switxch on/off.

It have made a spark. I did not go any further as I guess it's works

Just awaiting for the transformer and then will need some help to understand safe way to remove old one and replace it without damaging the board

I have asked Marini if the proposed transformer on amazon was good replacement and they confirmed that. Shall we trust them?

 

[Jonny weld]

Component just arrived. What best method to safely remove the old one?

 

[voipio]

Soldering iron and solder braid and/or solder sucker, plus some multicore solder, to remove the transformer. Alternatively, apply a gentle pull to the transformer and use a soldering iron to melt the solder around each transformer pin in turn, rather like tightening up a cylinder head. The transformer will lift off the board, bit by bit, and eventually come off. Wrecutters or a dremel curring disc could be used to speed up the process, not that it takes too long to do, anyway.

Having a second person and using two soldering irons would allow one side of the transformer to be lifted free of the circuit board in one go. A hot air rework "pencil" would be another method of removal, playing the airstream over two pins, until the solder melts.

 

[Jonny weld]

Soldering iron and solder braid and/or solder sucker, plus some multicore solder, to remove the transformer. Alternatively, apply a gentle pull to the transformer and use a soldering iron to melt the solder around each transformer pin in turn, rather like tightening up a cylinder head. The transformer will lift off the board, bit by bit, and eventually come off. Wrecutters or a dremel curring disc could be used to speed up the process, not that it takes too long to do, anyway.

Having a second person and using two soldering irons would allow one side of the transformer to be lifted free of the circuit board in one go. A hot air rework "pencil" would be another method of removal, playing the airstream over two pins, until the solder melts.

I have a rework station. Do you reckon putting the board upside down and working from soldering side. with hot gun should be able to get it drop down?

 

[voipio]

I have a rework station. Do you reckon putting the board upside down and working from soldering side. with hot gun should be able to get it drop down?

The transformer probably won't drop straight out, but some gentle (and I mean gentle) help with a flat bladed screwdriver, would ease its passage off the board. Take care not to overheat the board. Set the hot air gun temperature to around 380degC.

 

[Seadog]

The transformer probably won't drop straight out, but some gentle (and I mean gentle) help with a flat bladed screwdriver, would ease its passage off the board. Take care not to overheat the board. Set the hot air gun temperature to around 380degC.

If you're anything other than careful, then there is the potential of pulling the track from the board.

 

[Jonny weld]

All,

I haven't touch it yet as got busy with work.

Trying to do it today. Set two soldering gun at around 300 degreeC but the old lead won't melt. Do I'm doing something wrong. Do I need to buy some flux or product to put on the old lead before trying to melt?

Thanks

 

[voipio]

The soldering iron needs to be hotter. Try 350-380degC. Also, the tip of the iron needs to be tinned first, with flux cored solder, wiped on a damp soldering iron sponge, and tinned again. Repeat until the tip is properly tinned, then apply some solder to the tip before applying to the transformer solder joints.

 

[Jonny weld]

The soldering iron needs to be hotter. Try 350-380degC. Also, the tip of the iron needs to be tinned first, with flux cored solder, wiped on a damp soldering iron sponge, and tinned again. Repeat until the tip is properly tinned, then apply some solder to the tip before applying to the transformer solder joints.

I put it to 380degC and it worked fine. Not alot of experience with that kind of soldering but slowy slowy it dropped down. Two man job melting those pin almost at same time.

Put it back on the mig and seems working fine.

Well done to everyone who contributed to this fixing.