Miller Synchrowave 180SD trouble

[madderscience]

Hello all-

I have a Miller Synchrowave 180SD. I bought it new, and it is about 10 years old now. I am a home/hobbyist user so it hasn't been abused or overloaded. (Though I've certainly done my share of projects with it, it is a great tool).

Unfortunately it has started acting up recently. When in TIG mode (which I use almost exclusively) what happens is that the "throttle" control (OEM foot pedal) seems to have no effect. When I step on the throttle even just slightly, the welder comes on "full throttle" and acts more like a cutting torch than a welder. blowing holes in everything and slinging slag everywhere.

This started out as an intermittent problem but now it does this most of the time, regardless of temperature, DC-/AC/DC+ setting, the position of the current limit knob, or any of the other things I have fiddled with.

I did try gapping the spark gaps, but to no avail.

Looking at the circuit diagram, seems like the only internal thing(s) that could be wrong are 1) a shorted SCR module preventing modulation of the welding current, or 2) a bad control board. The only external thing that might be wrong is the foot control itself. Not sure what I would need to do to troubleshoot any of these items.

Any ideas?

Thanks to all an advance.

Brian H.

[cruizer]

Control board is hooped,

[Miller servicedude]

Hello all-

I have a Miller Synchrowave 180SD. I bought it new, and it is about 10 years old now. I am a home/hobbyist user so it hasn't been abused or overloaded. (Though I've certainly done my share of projects with it, it is a great tool).

Unfortunately it has started acting up recently. When in TIG mode (which I use almost exclusively) what happens is that the "throttle" control (OEM foot pedal) seems to have no effect. When I step on the throttle even just slightly, the welder comes on "full throttle" and acts more like a cutting torch than a welder. blowing holes in everything and slinging slag everywhere.

This started out as an intermittent problem but now it does this most of the time, regardless of temperature, DC-/AC/DC+ setting, the position of the current limit knob, or any of the other things I have fiddled with.

I did try gapping the spark gaps, but to no avail.

Looking at the circuit diagram, seems like the only internal thing(s) that could be wrong are 1) a shorted SCR module preventing modulation of the welding current, or 2) a bad control board. The only external thing that might be wrong is the foot control itself. Not sure what I would need to do to troubleshoot any of these items.

Any ideas?

Thanks to all an advance.

Brian H.
Try unplugging the plugs at the board and pull on each wire just to make sure it is seated all the way in the plug. Also do the same at the hall device HD1.

[madderscience]

Hi Kirk, et al. thanks for the suggestions.

I took the cover off my welder, and inspected and re-seated all the plugs going to the control board and to the hall effect device. I actually took the control board out and visually inspected it too, it appears fine. (nothing burnt, physically damaged, etc). In fact, except for a very light layer of shop dust (which I cleaned out), everything looks new.

I also tested the foot control. Its switch (pins A,B) and 1K variable resistor (pins C,D,E) work fine both when measured from inside the foot pedal and from the plug itself.

The problem is still happening though.

Any further ideas? I am reasonably adept with digital electronics and electronic troubleshooting so if there is a test procedure I can run to help diagnose the problem, please advise.

[Miller servicedude]

Can I get the serail number from you please ? Thanks.

[madderscience]

serial number sent via private message. Thanks.

[madderscience]

Hi Kirk-

I followed your instructions to test the voltage across pins 10 and 12 (wires 29 and 4) on plug RC1 when the unit was powered up and welding. (Note to others who might be having this problem: your diagnostic process, schematics and connections may vary)

You stated that I should see 2VDC for every 100A of welding current. since the welder is stuck running full blast I expected to see about 4V.

In fact, I see 0 (zero) volts. I know the test connections were good because there is a brief voltage spike to about 4V when I turn off the 220V supply.

I tried slightly moving back and forth both of the trimmer pots on the hall effect device in case perhaps they had oxidized and were not making contact, but this had no effect.

So is this a strong sign that the hall effect device is bad? Does this completely rule out the control board? (I hope!)

Thanks.

[Miller servicedude]

Hi Kirk-

I followed your instructions to test the voltage across pins 10 and 12 (wires 29 and 4) on plug RC1 when the unit was powered up and welding. (Note to others who might be having this problem: your diagnostic process, schematics and connections may vary)

You stated that I should see 2VDC for every 100A of welding current. since the welder is stuck running full blast I expected to see about 4V.

In fact, I see 0 (zero) volts. I know the test connections were good because there is a brief voltage spike to about 4V when I turn off the 220V supply.

I tried slightly moving back and forth both of the trimmer pots on the hall effect device in case perhaps they had oxidized and were not making contact, but this had no effect.

So is this a strong sign that the hall effect device is bad? Does this completely rule out the control board? (I hope!)

Thanks.
Yes, I think so.

[cruizer]

You don't really want to touch the trimmer pots on the hall, and if you do you want to make sure they go back to the exact same position. Just to let you know though, there are very few problems with the halls.

I've worked on many of the 180SD units and what you are describing is a control board issue. That said, if Miller were to send you out a hall to try, and if it wan't the case you could always get a new control board, as parts cannot be sent back to Miller once unsealed from the static bags.

Did you check to see if the board was supplying the +15 Vdc and the -15VDC to the hall. I'd guess it's not there.

[madderscience]

I did test the supply voltage side of the hall effect device. However, the supply voltage (30V) was as expected per the hall device's specifications and cruizer's suggestion. A more sensitive volt meter shows about 180 millivolts of output on the hall effect device when the welder is running, but this is way lower than the 4v expected at full blast. The impedance of the inputs on the control board from the hall device is high enough there is no reason why the full 4v should not be there. I'm pretty convinced it is the hall device now.

I have replacement hall effect device on order from digi-key ($25 plus shipping). I'll post again when it shows up and I can put it in. Heres hoping I can get back to the project I really wanted to be working on.

Stay tuned.

Thanks all.

Thanks all.

[cruizer]

You have to use the one from Miller, as it's speced for the board, or you'll toast both the control board and Hall in a quick and smokey fashion.

Your not seeking 30 volts, your seeking +15 & -15 Vdc to the Hall common.

[cruizer]

Now if your unit is running full blast, and the hall was putting out a 0 signal, thats what you would get as an end result on your output studs. You are not reading it right

Check the input to the hall!

[griff01]

You have to use the one from Miller, as it's speced for the board, or you'll toast both the control board and Hall in a quick and smokey fashion.

Your not seeking 30 volts, your seeking +15 & -15 Vdc to the Hall common.

It amazes me that someone would ask for free advice and then send their money to someone else. The board will, as you well know, be much more than any possible savings found by purchasing from Digikey. Wow.

Griff

[madderscience]

Final update here:

I got the new hall effect device today. Same manufacturer, same exact part number as the failed unit. I put it in, and the welder works perfectly.

Thanks to all who provided advice.

As for the comments about my choice to spend 1/3 as much on an identical off the shelf part from a 3rd party, consider that my next major tool purchase is likely to be a brand-spanking new miller plasma cutter, which of course can only come from miller.

Thanks again to all.

[duaneb55]

Thanks for the update Brian and good job to you and Kirk. I hope you don't mind if I call either of you if I ever experience a problem with my 180 SD.;)

[Miller servicedude]

Thanks for the update Brian and good job to you and Kirk. I hope you don't mind if I call either of you if I ever experience a problem with my 180 SD.;) I'm glad that it worked out. If anyone ever needs any help with their tig machines just let me know. Thats why I'm here. Thanks.

[cruizer]

Something is fishy here, you can't just pop aa replacement hall into a machine without spec'ing to that board