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XMT304 Help7

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  • #46
    Well, that's progress at least! Something is overloading the +15V supply. it should be a solid 15V, absolutely not 12.9V. When the supply voltage drops, the bus unbalance detection circuit can give a false trigger, which explains the help7.

    I'm way too tired now to poke at the schematic and see what else you should check, will see if I have time tomorrow morning.

    I don't have the correct schematic for that serial number, so I can't look up what R250 is. I wish miller would make it available, or someone on here could find a copy and scan it...

    If you can, try getting a thermal image of the front control board.

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    • #47
      My *******s neighbors didn't let me get any sleep again last night due to their 24/7 party, and I'm too tired to function, much less analyze schematics. maybe tomorrow.

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      • #48
        R250 looks to be in the same location on your board as the board in the TM. It looks like it is in the 230V contactor power circuit.
        Last edited by jjohn76; 08-25-2020, 08:12 PM.

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        • #49
          Okay I tried to get a good thermal image of the front board but couldn't figure out a good way peaking in from the sides, no components stood out as hotter than others

          I did remove PC2 so i could test the diodes from the back and got some results. D1 showed 320kohms in one direction and 77kohms in the other direction. D2 showed 220ohms in both directions which I think is definitely not good. The manual shows that both are supposed to test at 2000ohms.

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          • #50
            Harry, just use your diode tester. I'll check out my spare PC2 in the morning, but I don't think anything is in parallel with those diodes once PC2 is removed from the machine. You're really confirming they aren't showing 0 ohms.

            Measure both directions from R1 to L3-2, then measure both directions from R5 to L4-2.

            If you still get the same readings, please post pics if what you are measuring.

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            • #51
              Also, it's worth pulling RC4 off PC-1 and checking resistance across pins 4 and 2, as well as pins 1 and 3. Resistance should be 7.5 ohms.

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              • #52
                Originally posted by jjohn76 View Post
                Harry, just use your diode tester. I'll check out my spare PC2 in the morning, but I don't think anything is in parallel with those diodes once PC2 is removed from the machine. You're really confirming they aren't showing 0 ohms.

                Measure both directions from R1 to L3-2, then measure both directions from R5 to L4-2.

                If you still get the same readings, please post pics if what you are measuring.
                I did also check it in diode mode on the multimeter and got D1 OL and 0.33v and D2 0.084v and 0.087v

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                • #53
                  D2, or something in parallel with it, sounds distinctly unhealthy.

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                  • #54
                    Can you post pictures of your board, particularly around D2 and the PM2 connections? The board and schematic I have show nothing in parallel with D2, just want to confirm your board is the same. Also, have you checked PM1 and PM2 with the board off?
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                    • #55
                      Originally posted by jjohn76 View Post
                      Can you post pictures of your board, particularly around D2 and the PM2 connections? The board and schematic I have show nothing in parallel with D2, just want to confirm your board is the same. Also, have you checked PM1 and PM2 with the board off?
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                      I’ll try after work today to check PM1/2. I did measure RC4 with PM2 removed and I got 16.6Mohms and 16.4Mohms respectively.

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