How to modify your Miller Synchrowave so the TigRunner cooling system is switched on/off automatically when you switch between TIG/STICK modes.
If you switch back and forth between TIG and stick welding frequently and you value a quiet working environment, you are probably plugging and unplugging the TigRunner water-cooling unit every time you switch welding modes. You just don't want to listen to that water pump running when you're stick welding.
It's a straightforward process to modify your Synchrowave welder so that one side of the 115VAC power outlet is automatically switched on when you put the welder in TIG mode and off when you put the welder in Stick mode.
There's really only one component needed (besides a few wires) to make this modification....a solid state relay capable of handling at least 10 amps and operable by a DC voltage of 5 volts. The one pictured, available from Marlin P. Jones for about $7 is rated at 25amps and can operate with a control signal anywhere between 3 and 32 volts DC.....i.e. it's perfect.
To make the modification you have to remove the left side panel (as viewed from the front) and the top part of the welder's enclosure. You also have to remove the 6 bolts that hold the front output panel in place....but all you have to do it tilt out the output panel. It is not necessary to disconnect any of the many wires that lead to this little panel. This photo shows my Synchrowave 250 DX with the two cover pieces removed and the output panel tilted out.
Here's a close-up of the tilted-out output panel showing the backside of the 115VAC outlet (left) and the solid-state relay (right) that I mounted to the output panel using a single screw through an existing hole (thanks, Miller!). On the 115VAC outlet, you want to break off the coupling tab on the HOT side of the outlet (the side away from us in the photo - you can't see that tab in this photo but you can see the identical tab on the NEUTRAL side in this photo - it's the little brass "bridge" that connects between the two screws). That separates the two outlets electrically. Now, take all of the wires that were previously connected to the hot side (three on my welder) and connect them all to the LEFT screw on the hot side. In addition, connect a new wire about 10" long to the LEFT screw and run it over to one side of the solid-state relay (that's a black wire in the photo above). Run another new wire from the other side of the solid-state relay over to the RIGHT screw on the 115VAC outlet. Frankly, this little bit of screwing turned out to be hellishly tedious because there's not enough room to permit the usage of an ordinary screwdriver. I had to use a right-angle screwdriver and rotate the screws 1/4 turn at a time.....whew!
However, when finally completed, you will have arranged things so that the LEFT 115VAC outlet is always powered up while the RIGHT side of the 115VAC outlet is only powered up when the solid-state relay is activated. Now connect a pair of wires, color-coded red-black for positive-negative to the DC control input terminals of the solid-state relay and route them off to the left as shown in the above photo.
Looking from the left side of the unit, the control wires, twisted together for noise immunity, are run upwards along the existing wire harnesses until they reach the left side (viewed from the front of the welder) of the main circuit board that sits right behind the front panel controls of the welder. These wires are going to be connected directly to the points on the circuit board that power the LED that comes on when the welder is in TIG mode. This LED is connected in series with a 2k ohm resistor and the control circuitry activates the LED by applying 5 volts to the LED-resistor combination. It is this 5 volt signal that we want to tap into to sufficiently activate our solid-state relay. It might be marginal to simply connect the wires across the LED itself because there's only about 3 volts across the LED when it's lit. So we want to connect across both the LED and its associated resistor.
Apologies for the focus on this photo but it should suffice to show you the exact location of the desired contact points on the circuit board. If there is any doubt, CAREFULLY monitor the suspected points with a voltmeter while running the welder and switching between TIG and stick modes. BE CAREFUL sticking your nose into this powerful monster when the covers are removed and the power is on. 230VAC can kill you very quickly. If your circuit board is coated with a clear varnish-like material, it will be necessary to scratch through that coating to make contact with the voltmeter probes. When you find the right points (one of which will necessarily be one side of the LED), you will see 5 volts across them when the TIG light is on...and zero volts across them when it is off. Note which point is positive and which is negative (as I have done in the photo above) and CAREFULLY solder your control wires onto the back side of the circuit board (which means you don't have to take the circuit board off!!!).
That's it! Plug your TigRunner cooling system into the RIGHT side of the 115VAC outlet and it will automatically be started when you switch the welder into TIG mode. Cool, huh?
....and you still have the left side of the 115VAC outlet always powered up to run your grinder, radio, etc.
NOTE: I checked with Miller about this modification and, while they stopped short of actually recommending this modification, they were good enough to provide me with the schematic of the main control board and a data sheet on the IC that drives the LED indicator lights. It is clear from that information that the additional 8-10 mA that the solid-state relay draws is well within the rated capabilities of the circuit. In other words, this modification isn't going to hurt the welder.
Feel free to contact me if you have questions.