MIG-130 feed motor PCB GI-PCB-H59-A0 repair (old: Help me with capacitor replacement)

[stj]

Re: Help me with capacitors replacement

a pcb mounted fuse is a good idea if this keeps happening

[Per Hansson]

Re: Help me with capacitors replacement

Yes there is room but as you said Per I need to take an extra look at your work. but you say "I would put a regular bridge rectifier" of what value if you were to recomendera?

It does not matter, the original is only rated for 2A so it should be more than that.
But any bridge rectifier you have in that large package I showed is going to be rated for more than that...
I would go with one rated for 1000v just because the original seems to be.
And not because the circuit requires it, but because in a welder you have very large voltage spikes, and that could destroy the diodes...
Infact it might be good to put some TVS protection, for example a varistor across the bridge rectifiers input.

[bohaboha]

Re: Help me with capacitors replacement

a pcb mounted fuse is a good idea if this keeps happening

there is already a fuse but it was not destroyed by the shock

[bohaboha]

Re: Help me with capacitors replacement

It does not matter, the original is only rated for 2A so it should be more than that.
But any bridge rectifier you have in that large package I showed is going to be rated for more than that...
I would go with one rated for 1000v just because the original seems to be.
And not because the circuit requires it, but because in a welder you have very large voltage spikes, and that could destroy the diodes...
Infact it might be good to put some TVS protection, for example a varistor across the bridge rectifiers input.

so one of them would fit? but I shall come back to you after a more detailed examination of your picture and of my own circuit

[Per Hansson]

Re: Help me with capacitors replacement

Yes sure, I'd pick the one with the longer legs, just because I could not find a datasheet for the other one.

[R_J]

Re: Help me with capacitors replacement

The one with the shorter leads is 6 amp 600v

[R_J]

Re: Help me with capacitors replacement

there is already a fuse but it was not destroyed by the shock

The fuse on the board is on the DC side of the bridge, there should also be a fuse on the AC input to the bridge, if not that would explain the destruction of the bridge rectifier. Looks like the board traces were the fuse in this case.

[redwire]

Re: Help me with capacitors replacement

I can't see upsizing the bridge rectifier because of the high (mains) voltage and the PC board bad design mean the spacings simply are not good enough. You need a couple mm at least or it will just arc. That leaves flying leads to connect to it I guess.

Second, then it will start a new problem - what now limits power to the feed motor, when it jams? You need a fuse or circuit breaker, otherwise something new will burn up. The triac has no heatsink either. This is a cheap board.
It seems to assume the feed motor only needs say 2A max.

What model name/number is this welder?

[bohaboha]

Re: Help me with capacitors replacement

I can't see upsizing the bridge rectifier because of the high (mains) voltage and the PC board bad design mean the spacings simply are not good enough. You need a couple mm at least or it will just arc. That leaves flying leads to connect to it I guess.

Second, then it will start a new problem - what now limits power to the feed motor, when it jams? You need a fuse or circuit breaker, otherwise something new will burn up. The triac has no heatsink either. This is a cheap board.
It seems to assume the feed motor only needs say 2A max.

What model name/number is this welder?

here some pictures of the aggregates with some data

[bohaboha]

Re: Help me with capacitors replacement

Check the attached photo, the clearance is a joke!
I would put a regular bridge rectifier like I have shown if there is room for it.
Then remove the traces so the clearance between them is more than a cat whiskers hair!
But you need to triple check my work, it is hard to tell if there are more traces on the top of the board...

Hi Per you say "Then remove the grooves so that the distance between them is greater than a cat's hair!" What do you mean by removing the grooves here?

[Per Hansson]

Re: Help me with capacitors replacement

Hi Per you say "Then remove the grooves so that the distance between them is greater than a cat's hair!" What do you mean by removing the grooves here?

I don't know where you got "grooves" from, I said traces.
You need to remove the traces according to the picture in my post.
Otherwise the clearance is too small and it will just arc over again.
This is the reason for using the bigger bridge rectifier:
Not because the circuit requires it: but because it will have more clearance and be much easier to solder in the way I showed:

https://www.badcaps.net/forum/showpo...7&postcount=17

[bohaboha]

Re: Help me with capacitors replacement

I don't know where you got "grooves" from, I said traces.
You need to remove the traces according to the picture in my post.
Otherwise the clearance is too small and it will just arc over again.
This is the reason for using the bigger bridge rectifier:
Not because the circuit requires it: but because it will have more clearance and be much easier to solder in the way I showed:

https://www.badcaps.net/forum/showpo...7&postcount=17

Forgive translation errors

[bohaboha]

Re: Help me with capacitors replacement

Hello and thank you all who helped Per Hansson solution worked I The machine is working as it should

[sam_sam_sam]

Re: Help me with capacitors replacement

Okay here is one thing you can do is to take a dermal tool with a round sander drum at low speed and carefully remove all of the carbon traces not the copper traces you have to be very careful not to remove to much of the board material just to remove the black which is carbon if you have to much material that you remove around the holes then you can put

[redwire]

Re: Help me with capacitors replacement

I would check the wire feed motor is working OK. It's looks pretty cheap, small and wimpy, made by Guangzhou Epower Motor Co.
I can't read the feeder part number, "___SSJ27"? to see what voltage the motor is. The only ones less than 1A are 220VDC, all the others are all 12-42VDC and several amps.
If you connect a DC power supply to the feed motor and see if it's not jamming or has bad brushes etc. that would prevent the new bridge rectifier from burning up. I think you have to mount it off the board and run wires to it, the PCB is wrecked too much.

[R_J]

Re: Help me with capacitors replacement

It is likely a 28SSJ27, 24v 10w (1/2 amp?), I don't think the fault is with the motor etc. if it was the dc fuse would have blown. More likely a good spike on the ac input took out the unprotected bridge rectifier. (copper traces for fuses)

[redwire]

Re: Help me with capacitors replacement

There's a good chance the transients are made by the welder itself.
Is OP's board for mains phase-control to power the DC feed motor? I see the welding transformer output is 20VAC low/30VAC max. but they didn't use it for the feed motor I guess.

Anyhow, it seems the spacings on the PC board are inadequate for mains voltages, and the bridge rectifier would not survive a jam on the feed. The fuse value we don't know.

[stj]

Re: Help me with capacitors replacement

so it needs a new board layout, and a polyfuse.
and an led+series resistor across the polyfuse to indicate an overload

[Per Hansson]

Re: Help me with capacitors replacement

With my previous post here doing a Google search you can find this page linked below for example.
That was why I wrote this welder seems to be designed like crap, especially no protection for the bridge rectifier when it comes to spikes and that a varistor should be added to it:
https://www.mig-welding.co.uk/forum/...-please.85827/

Here is a video of someone modding it with a transformer so the wire speed does not change as you are welding, based on the previous pages mods:
https://www.youtube.com/watch?v=y7UXTctu8V8

[redwire]

Re: Help me with capacitors replacement

I drew a schematic for the MIG-130 feed motor control pc board GI-PCB-H59-A0. OP's is almost identical, just a couple resistors deleted.
It's a cheapened copy of a Clarke 130EN MIG welder feed motor board. That welder also has a DC output, cooling fan.

Overall, not a decent design - I have seen it's easy to get 1k+ spikes out of a 24VAC transformer (welding) which kills rectifiers. Also missing is a back EMF diode across the motor.
So if this was mine, I would add an MOV or snubber across the transformer's output as well as 1N4007 across the feed motor.
The circuit has some silly parts it's obvious they are all copying each other without knowing how it actually works lol.
The SCR is normally full on, and the potentiometer voltage turns on the transistor which turns off the SCR. The big resistor gives some feeder load (jam?) sensing.