Settings & controls (Help!) OTC machine (CPTX 180)

[Junkyard Tom]

Hi, there, I'm new to this forum.I've just got an old OTC machine off FB marketplace. I am confused by the controls, settings and operation. It's a CPTX 180 which will run either 400v or 230v. It has a switch that seems to be "Power" (1-6) and wire speed (0-10), but also two other controls, on might be "pulse"(?? Dotted line and arrows up -down) and the other seems to be a pulse-setting on wire feed (dotted line thru rollers). Partly, just wanting clarity - so not just guessing settings. But main issue is that after trying ALL combinations of all switches, I cannot seem to get constant wire feed. Runs for approx. 4 seconds, then stops, then 4 seconds. With "wire pulse" (??) Swith at 10-and-a-half, the cut-out between 4-second bursts is short, but still present. At "1" it's a few seconds. Turning the know to "zero" there is an electrical "click" as the function powers off. In this position, the torch will run for the same 4 seconds, and then stop. Then you must release trigger and press it again every 4 seconds to make it work. I wonder if I have bought a machine intended for a specific or particular, weird industrial purpose? I am not a particularly good welder (haven't welded in 20+ years) so it doesn't help trying to get the hang of this that I don't understand how machine works and that it seems to work in a strange way. I NEED to learn to get good enough to do acceptable Welds to bodywork & chassis reasonably efficiently...I have a fleet of VERY rusty machines from the 1950s that need a LOT of welding everywhere. I am hoping this machine can do what I need. 'Ve Googled the company OTC - Japanese, seem to do mostly industrial and not domestic / DIY machines. I cannot find details or manual for this particular machine. It seems good quality construction, and when I hit lucky with random switch selection, seems capable of OK Welds momentarily. But hard to replicate. And never feels right...feels like settings all wrong (as well as not being great at welding, it's hard to get hang of technique when settings are just guessed at and probably wrong). I know I'd do better with a more straightforward machine in good condition, but my budget is VERY low. Got this for £75, and that was pushing the boat out. Running it on a free bottle of pub-gas, which probably doesn't help. If I was a richer man, I'm sure there is a machine out there between £250 and £400 which would do what I need easier. But you gotta work with what you got, so I'm hoping Ican get this machine to do what I need it too, before my cars fall to bits. (Daily driver = the world's WORST 1958 Frogeye Sprite.)

 

[eddie49]

Hello, and a warm welcome to the Forum !

This should be a good machine ( if we can help you get it working correctly ), and any 180 Amp MIG welder for £75 is a bargain.
It does look like OTC Daihen are a high-end industrial/robotic Japanese welder company, see:

https://www.mig-welding.co.uk/forum/threads/otc-ac-mig-for-sale.108530/

The arrow on the "pulse wirefeed between rollers" graphic is pointing in the opposite direction to the wirefeed speed control, so I think it may be a Burnback Timer. When you release the torch trigger switch, the wirefeed stops immediately, but the arc current and gas flow continue for a short, variable, time. The MIG wire keeps melting back towards the torch tip, within the gas shroud. This stops it sticking to the workpiece and ensures a controlled short wire length ready for the next weld operation. If it does manage the burnback delay, this control will probably not have an "Off" function, but when set at zero there should be no delay, i.e. wire, gas, and arc should all stop immediately on release of the trigger.

The "Up arrow, Dots, Down arrow" control could be a Spot Weld Timer. This should run the welder for a short, pre-determined, variable time after squeezing the trigger, and then stop it. During this time, you will be circling the weld pool within an 8mm hole in the top sheet, to simulate a spot weld. This is known as a plug weld.
However, you are observing that this on-pulse is about 4 seconds and it keeps repeating, which would be known a Stitch Welding. For me, 4 seconds sounds like a long stitch, and the knob appears to only control the gap, as opposed to the stitch length. Normally a stitch function has two controls, so both the On and the Off periods can be adjusted.

Either way, as you expect, the "click" when set fully anti-clockwise should disable this option, and allow continuous wirefeed.
I would suggest:
- power-off and unplug the machine, look inside and remove all the covers, check for an add-on modification, a toggle switch somewhere that runs this timed mode continuously
- behind the front panel, locate the back of the "pulse" control potentiometer. There should be three connections for the variable-resistor function, and two connections for the On/Off switch. Use an Ohmmeter across those two wires to confirm that the switch conducts/doesn't conduct when moved from On to Off. This control may be free-standing, with wire leads, or it may be attached directly to the printed circuit board ( PCB ). Post internal photos if anything is not clear.

If that switch is OK, then there may be an electronic logic fault on the PCB which is keeping the pulse function enabled.