ReplyCheck the circuit breaker for the control circuit (CB#1 I think). If it is an HF model, check what position the amperage control switch is in. Are you using a footpedal?
Solderer
I have a Miller dialarc 250 AC/DC serial # HJ146996 that I've replaced the rheo already but machine is either all the way up when in high range or all the way down in low range. Please let me know where to start or if you've encountered this before
Master Welder
Check the circuit breaker for the control circuit (CB#1 I think). If it is an HF model, check what position the amperage control switch is in. Are you using a footpedal?
Miller Multimatic 255
Master Welder
Double check and make sure wire 38 is connected to the center rheostat terminal.
35 and 34 are the out side ones. If in the working range you have no control.
Check the breaker like Louie suggested. Then unplug the welder and remove the covers. should be a diagram pasted on the case. if not it will be in your owners manual. Need a owner's manual, go to Millerwelds.com and download a new one for your serial number. Find a test multi meter and look for 30AC on the SR2 bridge rectifier. will be a black block with 4 terminals or a orange stack of plates.
Left side top of center panel. wires 32 and 33 are 30vac. 343 and 35 are 30vdc.
with power off wires 35 to 38 should read very low ohms, almost dead short.
This will check out the control system. If this is all working the check High low switch. check wires 23 and 28 at the weld diode assembly should read low ohms in both high and low position. will open up as switch is changed. This checks the weld transformer and Mag-amp. OUTPUT voltage will not turn down until it is under a load. The mag-amp is a current transformer is series with welder output.
Inside the mag-amp are three windings, one command(control) and 2 current circuits. In low range they are in series. High range only uses one. so no out put in low range may indicate the second low circuit may have failed.
Move the coils around you may find a broken one.
