Miller Syncrowave 180 SD only making half amperage on TIG

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Today I came in to TIG a few small parts that I need to ship in the morning and my Syncrowave 180 SD is only making half amperage on TIG. Argh! I tried three different remotes and two different torches. Same results. It outputs about 75 amps at 15V when wide open. I've been burning 6011 and 7018 all week without any issues. It really couldn't happen at a worse time. It seems odd the voltage is maxed out but the amperage is less than half. AC voltage to the machine measures 240V (measured 245 actually). Any ideas what I should look for? Anyone every encounter this issue? Did my 180 finally bit the dust?

The manual doesn't say anything about low output in the troubleshooting section that I could find.Model Name: Syncrowave 180 SDSerial Numbers: LC578819 through LE069546https://www.millerwelds.com/files/ow.../O360D_MIL.pdf
Reply:Were you trying to weld TIG DC on steel/stainless using EN?  Did you try AC or go back and try stick welding with it on DCEP again?  If none of the experts check in soon it wouldn't hurt to pull the wrapper and look for loose wires and look at the big rotating switch that moves when you rotate the process selector lever...make sure nothing looks odd there.  The fingers on that switch seem to attract all kinds of junk....wouldn't hurt to wipe them off and make sure everything is making proper contact.I doubt the machine is really dead...not much that can't be fixed on them.Check out my bench vise website:  http://mivise.comMiller Syncrowave 250DXMillermatic 350P with XR AlumaProMiller Regency 200 with 22A feeder and Spoolmatic 3Hobart Champion EliteEverlast PowerTig 210EXT
Reply:It burns rod no problem. No joy DCEN tig. I didn't try AC. I found a few posts over on Miller's forum that suggests this low amperage issue is a control board problem. I pulled the board to check number/version and I don't see any obvious damage. Everything looked tight and clean on the chassis. I sent out a RFQ to a few repair places that have experience with this board. I'll see what they say. I'm definitely going to check all the diodes before I send it out.



Reply:Before you attempt to have the pcb repaired. pull the rc6 plug and see if you can see the foot control with your ohm meter. since it is turning on we know A and B are ok.we need to check the pot circuit. If it test ok then the problem is on the pcb. if E is open between the control pcb and the foot control then check the wiring and 14 pin plug connections. Provided you can still stick weld to over 100 amps.If you can stick weld at any amps you set it at with no problems then we know part of the control pcb and the hall device are operating correctly. only the remote control input is messed up. Could be just the electronic switch on the pcb that switches from panel to remote control. or the buffer that drives the foot control.C to D at the 14 pin plug should be 10 volts. Pin 4 and 5 on rc6 should be your 0 to 10vdc signal to the pcb. If you want check A1 on the pcb pin 7. see if there is a signal that goes up and down with the foot control. my guess it has failed.
Reply:

Originally Posted by ccawgc

Before you attempt to have the pcb repaired. pull the rc6 plug and see if you can see the foot control with your ohm meter. since it is turning on we know A and B are ok.we need to check the pot circuit. If it test ok then the problem is on the pcb. if E is open between the control pcb and the foot control then check the wiring and 14 pin plug connections. Provided you can still stick weld to over 100 amps.If you can stick weld at any amps you set it at with no problems then we know part of the control pcb and the hall device are operating correctly. only the remote control input is messed up. Could be just the electronic switch on the pcb that switches from panel to remote control. or the buffer that drives the foot control.C to D at the 14 pin plug should be 10 volts. Pin 4 and 5 on rc6 should be your 0 to 10vdc signal to the pcb. If you want check A1 on the pcb pin 7. see if there is a signal that goes up and down with the foot control. my guess it has failed.
Reply:I pulled one leg of the protection diodes on RC6. Diodes D1 thru D3 and good and D4 has failed shorted. The diodes are P6KE12A.Looking at the datasheet they fail shorted.https://m.littelfuse.com/~/media/ele...asheet.pdf.pdfSo I'll start by replacing the TVS diode. Hopefully the diode did it's job and protected the LF347N quad op-amp.


Reply:

Originally Posted by forhire

I pulled one leg of the protection diodes on RC6. Diodes D1 thru D3 and good and D4 has failed shorted. The diodes are P6KE12A.Looking at the datasheet they fail shorted..]
Reply:

Originally Posted by John T

LOL... you are a nut. I KNEW you would be inside that thing... You will get it figured out. thanks for the pics and walk along....  I love your threads... always interesting.
Reply:

Originally Posted by forhire

Thanks. I ordered the parts today. The diodes were 32 cents. Even ordering 10, and springing another 60 cents for the op-amp, just in case, I still spent more on shipping than the parts. These diodes are tvs (transient voltage suppressor) and fail shorted. The good ones measure about 0.6V in the forward bias and block in the reverse. The bad diode measures about 0.3V in the reverse direction. Because the reverse is around 50% of forward, and it is a protection circuit, I suspect this is why I'm seeing 50% output on the weld current. I'm thinking it's just this diode. We'll see once I have the parts installed. It will either be smiles or tears.


Reply:Small world... my diodes are uni-directional. Good fix.


Reply:

Originally Posted by forhire

Small world... my diodes are uni-directional. Good fix.


Reply:

Originally Posted by ronsii

Thanks

  You did a great job of tracking down the failed component yourself

When I have to change out dip components I go ahead and pop in a socket just for the fun of it  

although I usually do it on more 'indoor' computer stuff

... hard to say if it might cause more problems with how a welders environment usually is

or maybe you could dielectric grease the whole thing to head off any issues of corrosion affecting the socket connections??
Reply:My theory was correct. I replaced diode D4 and I can now tig af full power. It is fixed.

I haven't put any time on it since fixing it this afternoon but due to how the TVS diodes fail shorted, and the short measured 50% of the forward bias, and it was clipping the output about 50%, I'm fairly confident I have it licked. It sure beat shelling out $500 bucks to send it out. Hopefully this helps anyone else with a similar issue.Hopefully it's good for another 20 years.


Reply:

Originally Posted by forhire

My theory was correct. I replaced diode D4 and I can now tig af full power. It is fixed.

I haven't put any time on it since fixing it this afternoon but due to how the TVS diodes fail shorted, and the short measured 50% of the forward bias, and it was clipping the output about 50%, I'm fairly confident I have it licked. It sure beat shelling out $500 bucks to send it out. Hopefully this helps anyone else with a similar issue.Hopefully it's good for another 20 years.


Reply:

Originally Posted by ronsii

Good to hear!!!   so are you going to change the other diodes now as long as you have parts and so on??? or maybe it's better to leave it and then if/when the other\s fail you're all ready to fix it ??  


Reply:Great to hear it worked out with not a lot of $ out the door. Thanks for posting up the solution.

Syncrowave 250DXMiller 330 A/BPMiller Big Blue 251D
Reply:

Originally Posted by Kelvin

Great to hear it worked out with not a lot of $ out the door. Thanks for posting up the solution.