Esab MigMaster 250: No 24v?

admin

Ive had this thing lurking in my shop for over a year. It needs to work or go. When you power it up the fan comes on. Last summer I tested the SCR's and power input side and it all checked out. I had a guy with decades of electrical machine experience helping with that. We couldnt get anything on the feed side. No 24v anywhere. We tested the trigger circuit and that was good. Then he got busy and the machine got rolled into a much needed corner. The k2 and k3 relays are new and were replaced by the PO. The originals were left inside and we tested both new and old. They all checked out fine. My friend didnt get around to messing with the board, but it passed a visual inspection. Nothing obviously burned out. This is going by memory. I rolled it out today and am scratching my head here. The standard/spool gun switch works. The slow blow 10a fuse is fine and i remember us jumpering it for testing purposes. Still nothing. It is correctly wired for 230v configuration and has no spot timer or anything special. Ive also tried researching this problem and all I can find is a potentially bad PCB. But what damages the PCB?
Reply:Here is hopefully what you are looking for.I Fix Stuffwww.millerserviceparts.comwww.lincolnwelderrepairparts.com
Reply:Here a link I found:https://www.esabna.com/literature/ar...f-15-087-e.pdfThe schematic for the manual in my link shows only TS1 (re-settable thermal switch?) and not two (TS1 + TS2) as shown in the schematic provided by Diode for the 24V coil.  Odd that they would use two thermal switches in series to protect the 24V coil in addition the the 10A fuse F1.Do you get 24VAC at the coil? Bypassing the thermal switches to test?Last edited by Denis G; 05-11-2021 at 09:15 AM.
Reply:24vac at black and red going into bridge. Thermal switches might be located at motors, feedmotor , and spoolgun ? FU1 probably located on PCB looks like a SMD Ptc(resettable) connected to PL1-10, and FU2  a PTC through hole(looks like a cap) connected to PL1-3FU1 :FU2 :good luckAirco 250 ac/dc Heliwelder Square waveMiller Synchrowave 180 sdMiller Econo Twin HFLincoln 210 MPDayton 225 ac/dcVictor torchesSnap-On YA-212Lotos Cut60D
Reply:Thanks gents for the info. I am going to try and sit down and study it this week. I'll be honest, Im not electronics savvy so I don't totally follow but I will do my best. Sent from my moto e6 using Tapatalk
Reply:check the connection in plug1 pins 5 and 10. take the cap off and push the wires into the plug. Relay K2 must close and connect pin 5 to 10 or the wire will not feed.Use a small screw driver and push the wire into the plug. the pins are self stripping.and have to cut through with wire insulation to make connection.test pin 8 to 9, should read 24 vdc to 33vdc. this is the power that runs the pcb.24 vac times 1.414 = peak DC voltage. if voltage is 23 volts the filter cap is bad or not connected.
Reply:Yeah I have 33v to the board but nothing to k2. I'm assuming this means the board is bad?Sent from my moto e6 using Tapatalk
Reply:Coil voltage to K2 and K3 is 24vac. spoolgun switch needs to be in regular not spoolgun. Make sure the spot timer jumper plug is making good connection. If you do not have a spot timer. what and were are you measuring on K2?Both K2 and K3 should pull in at the same time with the gun trigger. trying to measure a DC voltage with the meter set in AC will not read right. opposite also.