trouble with dcen conversion on 90 amp

Tue, 31 Aug 2021 09:05:45 GMT

go to see Welding Machine for trouble with dcen conversion on 90 amp

i have a 90 amp hf welder, 68887 if that matters, and i used it for 2 years. never overheated, only on 2nd spool of wire, could almost pass for brand new. i changed the power cord to exit the back of the unit, not sure why it didnt come that way, moved the fan motor to the outside of case, fan still inside turning same direction, basically just moved back 2 inches to make room for the rectifier, and built a shroud for the fan. last night i fired it up for the first time with the rectifier, and it did well, other than lack of penetration on 1/4 plate. my fault, havent given it a dedicated curcuit yet. today i fired it up, got a quick spot weld type burst then nothing. green switch lights up, fan runs, feeds wire, just wont arc. btw, it is a 150 amp rectifier. i dont have a cap on it, or a choke. need some advice  cause i dont know what to do. thank you.Sent from my RCT6203W46 using Tapatalk
Reply:I'm the newest noob here, but I'm also trying to learn and do the DCEN conversion.  If and ONLY if you know your way around electricity and a volt meter, 1) I'd first check the AC voltage INPUT to your rectifier.  If that's good..  2) then I'd check the DC output of the rectifier. and so on...I haven't begun to cut and assemble mine yet, but I've measured the AC voltage between my gun (no wire installed) and ground connections as I wanted to understand and size things like the capacitor.  I believe it was 22.5 (Low) and 27.9 (Hi) volts AC measured with a good DVOM.  I thought I've seen other reports of earlier models reaching 30-40 VAC (Hi).   I believe my AC measurement between the gun and gnd, would be the same as the wires you cut to connect to use for the rectifier input?I would assume that you'd have DC voltage on the output side of your rectifier pretty close to your input AC voltage.   Just for the sake of experiment, I hooked up a power cord to my rectifier input and plugged it into the wall receptacle.  Input was about 124VAC, output was 125VDC.    You are NOT going to see 120+VAC in, you will only have whatever voltage your welder's transformer is putting out.   I only did the experiment so that I could compare what is going into the rectifier bridge, with what is coming out.Again, I'd think your rectifier output DC voltage should be very close to your rectifier input AC voltage ?If it doesn't look good, perhaps your rectifier bit the dust?   If it does look good, then start checking the DC measured further up the line, until you reach the gun tip or you find the fail point.If the rectifier has failed, and you've got a 3 phase model, remove power and check all 3 of the diodes.  If only one of the two inputs your using has failed, could you use the 3rd input point as alternative?  Maybe one was weak?Be careful around that current.   I'm not a Dr, Electrician, Welder.. just a DIY'r.Last edited by bowfan; 05-05-2016 at 07:29 PM.
Reply:i appreciate the reply, i got it working again. i had to unhook one input and move to the middle terminal, so it appears there is something dead in my rectifier. btw, i ordered and paid for a 150, but recieved a 100 amp rectifier. looks like i lost the chinese lottery.Sent from my RCT6203W46 using Tapatalk
Reply:Originally Posted by xray51172... btw, i ordered and paid for a 150, but recieved a 100 amp rectifier. looks like i lost the chinese lottery.
Reply:If you are using a 3 phase bridge, I wonder if using it as 2 phase lowers the current rating to 2/3.
Reply:you made me curious, so i checked with my multimeter. i didnt actually weld in this test, just disconected power to the feed motor and pulled the trigger. on low- 22 volts in and 5 volts coming out of rectifier. hi- 27 in, and 7 out. Sent from my RCT6203W46 using Tapatalk
Reply:Everything I've read about this conversion tells me you need the capacitors.Miller Thunderbolt XL AC/DCHarbor Freight 90 Amp FluxCoreEvolution EVO380 Chop SawEvolution EVOMAG75 Mag DrillAHP Alpha TIG 200Xhttps://www.facebook.com/weldnstuff/
Reply:i built a bank of 4 22,000uf capacitors, and put in an on off switch. was welding and heard a pop, but it kept working so i didnt stop till i finished my bead. smoke was coming out and upon closer investigation, it apears 3 of the 4 caps blew out. before they went, i still couldnt get any penetration, starting to think maybe its not the machine.Sent from my RCT6203W46 using Tapatalk