Welding Tips and Tricks

I have an AlphaTIG 201xd that I'm using with a modified foot pedal and unfortunately I think it may have broke something.

I'm working on a hobby automated welder setup, which consists of programming the current control. I disassembled the NOVA foot pedal and interfaced a microservo to the potentiometer. While the final modification design consisted of the servo engaging the pedal switch immediately before it starts turning the potentiometer from it's zero position (identical to how it's used inside the foot pedal), I was doing some testing where I flipped and held the switch (i.e. arc starts and welding) while the potentiometer was already actuated at around 60% of it's travel. At first this worked fine and I was able to complete some welds without any issues, but soon after the welder started exhibiting some problems. Prior to these issues I had been welding AC aluminum with 3/32" electrodes and a CK WP-20 pencil torch, water cooled with a home built cooler. I'm on 120V.

I've done a considerable amount of troubleshooting so I will summarize my findings:

- The AC function does not seem to be working. When in AC mode, my tungsten gets obliterated and there's no buzzing, indicating that it's stuck in DCEP. Switching the torch and ground clamp (changing nothing else) confirms that it's stuck in DCEP, as it welds normally as if it were switched to DC.

- On AC, the display shows the current setting correctly but only up to around 75 amps. Turning the dial up from 75 through 200 doesn't change the display. On DC, however, the display shows all zeros no matter what the current setpoint.

- When welding on either AC or DC, the machine outputs what seems to be max current regardless of the current setting. The display shows about 170 amps after the arc gets started (and it looks like it is in fact outputting that), and changing the pedal setpoint doesn't change the current output. Because of this fact when the terminals are set normal (i.e. DCEN), the tungsten gets obliterated since it's actually outputting DCEP, again regardless of whether the machine is on AC or DC. I've replaced the foot pedal with the on/off finger switch that came with the welder, and it doesn't change anything.

So did I break my welder? I opened it up and don't see any glaringly obvious signs of electrical damage.

Can't say what's up with the stuck in DCEP mode, but if you're running on 120v, you won't get the upper amperage range on your box I'm afraid.

Order another foot-pedal to find out if you broke it. Unfortunately, it's part of playing the game when you're experimenting.

Sounds to me a lot like plain 'Bad Luck(TM)' and not much you broke.

The machine should have no issues with how a pedal works or is actuated. You should be fine with setting the pedal pot first and then triggering the switch like you did. Not much different from setting the amps on a front panel and then using a torch-switch to turn it on.

I would expect pretty much all welders to also be pretty rugged on the pedal inputs so even accidentally shorting pins should normally not cause any permanent issue.

Especially with it not producing A/C sounds more like something deeper inside the machine has gone bad on the inverter control itself and not some control/input issue. Although it would still be possible I guess if the design of the unit is not tha great from a de-coupling setup that it allows for external connection issues to propagate to control-components internally.

Bye, Arno.