Square Wave 355 No Arc

[Mavic]

Hi,

Looking for a bit of help. Just picked up a used Lincoln Square Wave 355. Finally got it all wired up and set up. But the unit will not generate an arc. Amp display is working, set it to around 200 amps. HF start is working (can see the ionizing arc but doesn't establish the welding arc) , gas valve is working as well, just not getting an arc started.

I did switch over to stick mode from tig and nothing there either. Looked at the troubleshooting in the manual and the only thing I could determine is there is no Open Circuit Voltage. I'm showing around 0 to 2 volts on the meter when the amptrol is depressed, when turned from full CCW to full CW. On a side note the amp meter shows only 410 while in stick mode can not change this value with the amp knob.

Any assistance would be greatly appreciate on what might be wrong even if it's operator error.

Thanks

[ccawgc]

Do you have the owner's manual. Go through the set up and trouble shooting sections.
This will help you make sure it is not a set up or operator error.
If you need one, take the code number to Lincoln's web site and down load it.
This is a complex older TIG welder. Depending on what tools and knowledge you have. You might be able to find out what is wrong. One thing you can try is unplugging the welder, take the covers off and get to the pc boards. Just unplug check the pins in the plugs and make sure they are pushed all the way in and then plug them back in. make the welder safe and retest it. If no change we will need to get deeper into it.

[Mavic]

Thanks for the response.

I have gone through the manual and checked out all the hook ups and trouble shooting this past weekend.

Did some testing the other night trying to isolate what the issue might be, so I'll paste in what configurations I tested and the notes I gathered from the test.

***Stick

Polarity:AC

Switch Settings: Panel, Stick, 2 Step, HF (Off), Start (off), Spot (off), Pulse(off), Crater Fill (off)

Amptrol disconnected

Display Lights: Arc Established (on)
Peak (on)

Meter Readings were 410 on the Amps and roughly 6 on the volts, though I could get this one to change slightly while rotating the polarity selector switch.

I am still seeing the static spark, looks like a weak fireworks sparkler, at one point i was able to establish an arc that was weak for about 1/2 seconds.

***Tig

Polarity: DCEN

Switch Settings: Remote, Tig, 2 Step, HF (Start), Start (off), Spot (off), Pulse(off), Crater Fill (off)

Amptrol Connected

Display Lights: (foot off of amptrol) No lights

(amptrol depressed) Gas/Water (on)
Arc Established (on)
Peak (on)

Meter readings were 200 amps (adjusted to this value) while the amptrol was in neutral and Voltage read 0 (zero). With the amptrol depressed the voltage changed to 410 independent of what was dialed in and the voltage read 2.

Still only have a gas and the high frequency arc at the torch head while trying to weld. I think I heard a short welding arc at one point for about a second but could not re-establish it again. The arc was weak enough that I couldn't see it through the welding lens.

Machine History
I purchased the machine from a fluid engineering shop. The shop area was very clean, but they did have a bench grinder about 6 feet away. There was a an accumulation of grinding dust on the inside of the machine. I used compressed air to clear this material out as be as I could with the panels removed.

I'm wondering if there is a high resistance in the contact wipers of the polarity switch. But I'm not sure about how the electrical side function to be producing the 410 amp reading during the attempted weld, unless the machine is attempting to run up amperage to get the correct output.

Your thoughts?

[ccawgc]

You need to get a good volt meter that has a diode test mode.
The fact that the arc Established light is on indicates there may be a short in the SCRs or across the out put. Check the output terminals to ground and each other.
• ARC ESTABLISHED LED goes on when the arc
is fully established and goes out if the arc goes
out. copied from Lincoln.
The output terminals should read around 50 ohms to each other. There is a 100 watt 50 ohm connected across them. It is used to make OCV possible. SCRs will only fire into a load.
Looking at the diagram. If you are getting a high amp / low voltage open circuit reading, then one of the bypass filter pcb may be shorted. Find the output terminals follow the weld circuit (work side) past the bypass pcbs and a choke to the shunt. The shunt looks like a piece of metal. It will have two bolts connection small wires to it. Also when you look close it will look like the center piece is saw cut 1/2 way through. The shunt is made out of 3 pieces of metal that are silver soldered together, the center piece is saw cut to calibrate it to a precise value.
So look for some kind of short between the shunt and the output terminals across to the torch side. Could be a path way caused by the metal dust that has carbonized and will need to be sanded off. or the insulator replaced. Send me private message if you want more help

[arc-heat]

If you still need help troubleshooting give me a call.