i see loads of you have had the same hassle i have had with the sip/cosmo's so i will share with you how i fixed mine
befor all of you ask questions i have spent quite a bit of time behind a mig,tig and mma torch. I was a rep for a welding supply co. and used to demo new welders to customers. i have used the latest pulse synergic migs so using my old cosmo for the odd job like patching a sill on one of mine or my friends old cars was useabe just!
i know the cosmo is a cheap diy unit.
now i dont work as a welding rep anymore and im back on the tools and i need somthing to build a kit car at home (13A plug). so i dug out my cosmo to see if i could get a good weld out of it.
i know the feed system is junk. when i have used it i know its erattic and it uses the voltage on the output of the transformer, ok loads of good migs work like this but with one main diffrence thay have a bigger better motor and control the feed to it loads better.
i know a bit about eletronics so i would take a look and if i could not fix it i was going to seek out a good s/h unit.
so the feed motor serges and bangs away as you weld causing a naff arc.
its like when a good units feed pcb its up the fruit.
serviced it and tryed ajusting the trimmer with no improvement
so i made a quick call to the workshop of where i used to work asking the engineer who fixes the welders what causes this, feed pcb he said what is it
so i told him with the reply "thay all do that coz there cheep ****"
after a chat he explained when the old welders brake down thay cant get the pcb's so thay usualy replace the components and try looking for a largeish capasitor on the board and check it
so i ripped the cosmo apart and guss what no big capastors on the feed circuit so i looked through whats in the circuit and theres not much there at all.
i googled my problem and found here. read quite a few posts and the psu modds will work but its making the feed control open loop (not ajusting to arc length) so i didnt think thats the route to go so i was going to fix it myself in my own way.
the problem is the tiny motor reacts too quickly to the voltage aplyed to it and theres nothing damping the supply from the main transformer so as the arc opens the voltage rises speeding up the motor until it shorts the filler wire and stalls the motor making the hole operation worse.
whats needed is some capastence in the circuit to smooth it all out but still react to arc length but not in a machine gun way.
so i niped off to maplins to get some bits
tried the trimmer mod first had a effect on the feed as it warmed up but didnt fix it but still worth it for the cost as the pot is right over at its end.
so i bunged i a 2200uf 50v cap across the motor feed and tryed it with a improvement so i added another in pararllel
sorted smoth arc and good fizz first time and the feed setting is not critical like it used to be all 6 settings worked ok with no feed ajustment
only problem as you may expect is im now getting an inch of stick out from run on so a relay was next and putting the cap's before the pcb with a diode to block discharge to the transformer and fitting a relay to stop and brake the motor.
befor all of you ask questions i have spent quite a bit of time behind a mig,tig and mma torch. I was a rep for a welding supply co. and used to demo new welders to customers. i have used the latest pulse synergic migs so using my old cosmo for the odd job like patching a sill on one of mine or my friends old cars was useabe just!
i know the cosmo is a cheap diy unit.
now i dont work as a welding rep anymore and im back on the tools and i need somthing to build a kit car at home (13A plug). so i dug out my cosmo to see if i could get a good weld out of it.
i know the feed system is junk. when i have used it i know its erattic and it uses the voltage on the output of the transformer, ok loads of good migs work like this but with one main diffrence thay have a bigger better motor and control the feed to it loads better.
i know a bit about eletronics so i would take a look and if i could not fix it i was going to seek out a good s/h unit.
so the feed motor serges and bangs away as you weld causing a naff arc.
its like when a good units feed pcb its up the fruit.
serviced it and tryed ajusting the trimmer with no improvement
so i made a quick call to the workshop of where i used to work asking the engineer who fixes the welders what causes this, feed pcb he said what is it
so i told him with the reply "thay all do that coz there cheep ****"
after a chat he explained when the old welders brake down thay cant get the pcb's so thay usualy replace the components and try looking for a largeish capasitor on the board and check it
so i ripped the cosmo apart and guss what no big capastors on the feed circuit so i looked through whats in the circuit and theres not much there at all.
i googled my problem and found here. read quite a few posts and the psu modds will work but its making the feed control open loop (not ajusting to arc length) so i didnt think thats the route to go so i was going to fix it myself in my own way.
the problem is the tiny motor reacts too quickly to the voltage aplyed to it and theres nothing damping the supply from the main transformer so as the arc opens the voltage rises speeding up the motor until it shorts the filler wire and stalls the motor making the hole operation worse.
whats needed is some capastence in the circuit to smooth it all out but still react to arc length but not in a machine gun way.
so i niped off to maplins to get some bits
tried the trimmer mod first had a effect on the feed as it warmed up but didnt fix it but still worth it for the cost as the pot is right over at its end.
so i bunged i a 2200uf 50v cap across the motor feed and tryed it with a improvement so i added another in pararllel
sorted smoth arc and good fizz first time and the feed setting is not critical like it used to be all 6 settings worked ok with no feed ajustment
only problem as you may expect is im now getting an inch of stick out from run on so a relay was next and putting the cap's before the pcb with a diode to block discharge to the transformer and fitting a relay to stop and brake the motor.
Last edited: