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Miller board help please

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  • #46
    Originally posted by Aeronca41 View Post
    Even if you find it, the likelihood that is your problem is probably low. You will go broke just replacing parts until you hit on it.
    ☹️ I will try and use some parts from other machines, to not have to spend a lot of money only time searching, testing, dismantling, etc, to try and fix it

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    • #47
      Originally posted by Franz© View Post
      No don’t have any similar parts on the 250ci board it looks like all are surface mounted

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      • #48
        The over temp sensor is the item circled in red.
        It does NOT reside on any board, it's taped onto the outside of the coli.

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        • #49
          Yes that picture is from another machine not the 250ci

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          • #50
            I opened the miller machine to see if they similar in parts and to see if the parts are in the same location, but not this board is inverted technology

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            • #51
              this is the video of The Hobart 250ci showing the problem I disconnected the fan to hear a buzzing sound

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              • #52
                I forgot to mention that I also disconnect the compressor, if all is connected the fan and the compressor, when I press the trigger only the cooling fan will engage like trying to cool the machine and the 2 lights will star blinking and when the temperature lights stops blinking also the fan will stop

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                • #53
                  Aggullar , hope you haven't given up yet . I have the same machine and problem you have. I have been working on it the last week or so and searching the net for ideas I come across this place. Anyways I have fixed many pinball cpu , lamp and driver boards , power supplies , jukebox boards but this Hobart is abit different than what I am used to. With no real troubleshooting manual it is tough. Mine power on green light , hit the trigger and fan takes off and power / temp lights start flashing for 15 seconds then fan stops and temp light goes out. When I first hit the trigger and hold the gun touching metal then there is a small brief spark but that is it . If you look at the board the 5+ light is on always when power in on , if you hit the trigger then the Pilot light and the one next to the 5+ go on and off .....that is when I get the spark at the torch . But the motor light and compressor never come on . Fan runs its 15 second cycle and stops . If I hold the trigger all the time then the fan never stops , but will after I release the trigger. Compressor checks out OK if powered by external power supply , so I know it is good. I have all new consumables and verified all wires in the torch are good end to end and trigger is good , all conections and plug pins are good. Man the solder is hard stuff on this board , but I removed the bridge rectifier and it tests OK , tested and the other transistors and all seem ok. Nothing heated . I'm looking at it through a bench magnifier so can see pretty good . There is nothing that resembles a therm resistor that I can see in the open or taped over on a coil . The relay clicks on / off . Next to the relay is RT3 , not sure what it is as it is sliconed splashed over and greyed so I can't make out the numbers but wild guess RT stood for resistor /therm I undid one leg and tried it but the unit is then totally dead won't power on , so that is not it . Once I soldered it back on then the unit is back up . What trips the Temp light when the thing is not working ? Seeing that brief pilot spark tells me it wants to start but something trips it off. And the only circuit not working is the compressor either plugged in or not . This surface mount stuff is difficult . I have a hot air station but am not a magician . My findings so far tell me the " thing " that trips the temp light is in the motor circuit . If it is the 4 sided chip main brain then no way we can fix that . I have also checked for solder cracks around all the pins on the board but all is good.
                  Last edited by Johnny Ringo; 12-27-2019, 07:55 PM.

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                  • #54
                    Thanks Johnny Ringo I did all the same test you’re mentioning and as you said there is something like a thermistor PTC OR NTC that is measuring the temperature on the machine but can’t seem to find it if it’s a chip well that will be much harder to test, but I will be trying to solve this PROBLEM ON THIS DEFECTIVE DESIGN MILLER BOARD

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                    • #55
                      This is another Miller board but this one is working, plus I notice some different components on this board

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                      • #56
                        HS14 and D47 are the different parts

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                        • #57
                          This is the part and I also think that maybe it’s the part that is faulty, but don’t know how to bypass it, will not want to get it worse

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                          • #58
                            Looking on another forum the Hobart forum this is a common problem on this machines and I think that it’s a engineering design error

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                            • #59
                              Are you saying it's the black relay? What does it look like underneath that relay, any of the solder through point look burned? Those tend to fail from overcurrent, which means something else is also pulling alot of current. It could be those big capacitors are shorting out. Are there any indications they are bad?

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                              • #60
                                No the relay is good I’m referring to the gray small part, I think it’s a thermistor

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