millermatic 250 OVERHEATED....!!!

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I was welding some .375 mild the other day and was going for a few minutes...and the a hiss and smoke came blowing out of the machine...!!!! i thought F**K...!!! i burned up the only welder i got... and had to rent one to finnish the job....now the job is done i want to find someone that knows what happened to it...???  is it serious damage or can i change out the caps and it will be fine...??? i thought these machines have overheat pertection....but i guess not..!!! so if these is anyone that can help please give my some pointers...thank you so much for reading this and good input is allways well appreciated....
Reply:It probably wouldn't hurt to give miller a call and check with their service people and get ideas from them as to what might have happened. It may be more than the caps if the failure cascaded through the main circuit board. Sorry I can't be more help.Regards,RobGreat Basin WeldingInstagramBlue weldersRed weldersMy luscious Table DIY TIG Torch cooler
Reply:cool thanks...it still welds but not with alot of power... i wouldnt trust the penetration but still strikes a ark and welds but the caps leeked oil and blew alot of smoke.....
Reply:You blew an output capacitor.  http://weldingweb.com/vbb/showthread.php?t=39389Change them all.Overheat protection is for the output rectifier and and main transformer.  A cap failure is typically just an overworked "tired" capacitor.Last edited by duaneb55; 12-15-2010 at 07:41 AM.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:thanks...!!!! that is good news...... the weld shop wanted $900 to fix it and no warrenty....WTF....!!! i found mallys for $12 right around he connere from my house.... ill put them in this weekend.... hell ya..!!!move over let me weld it...!!!!
Reply:I'm afraid we will be seeing more capacitor failures as time goes by.Many of the older machines are running capacitors that are 30 and more years old.The up side is that putting in new capacitors will usually restore the machines to run better than they have ran in 20 years.
Reply:No doubt Bluewelders and don't be surprised if you have to "re-learn" your machine settings tattoo for as BW said it may weld better than it has in years with new caps.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Did you ever resolve this issue?1st the unit does have overheat protection.If unit overheats, thermostat(s)opens, output stops, and coolingfan runs. Wait fifteen minutes forunit to cool. Reduce amperage orvoltage, or duty cycle beforewelding.2nd typically bad caps most of the time will not cause the unit to require more power to lay a weld more so it will cause inconsistent welds. Reason is the Caps only clean up the DC voltage. Unless maybe you have burn to many out. A cheap check is to buy a Cap tester and remove the caps from the unit. Inspect them over well looking for buldgeing tops or any signs of leaks. a local shop should be able to test your caps for next to nothing if you already have them out. It never hurts to change them all since ripply power can cause poor welds.One common issue with the millermatics wanting more power to lay a weld is the SCR. or also know as the rectifier assembly. That assembly is actually 2 SCRs and it is possible the 1 could burn out and the machine run off of only 1. To main PCB will try to compensate for the lost SCR. You may not be using more power more like you have to turn it up more to get it to weld. All you are doing is pushing more power threw the 1 remaining SCR.You can find the schematics for your machinehttp://www.millerwelds.com/om/o1308n_mil.pdfYou are looking for part# 173 713 . RECTIFIER, SCR mainon page 18+19Don't let a weld shop fool you into paying $900 for a repair that you can do for not even 1/2 that cost. Those machines are not very complicated compared to other welders. All it really has is a transforms SCRS, caps and a few boards that control the machine.
Reply:thanks everbody for the input ill be working on it next week and will see what happens and ya the weld shop wanted $800 to fix it and no warrenty....what a joke but a little resurch and good input from guys like you it saves money and BS...!!!! ill keep you informed... thanks again....move over let me weld it...!!!!