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Thread: MEP 804A lots of issues.

  1. #11
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    I went thru the checks. First, I get 24v on A5-20 all the time start or run. I get 0v on A5-18 all the time start or run. I also get 14VAC at A5 from the MPU .I did the quick Frequency adjustment and now operating at 60hz, it looks like it needed one full turn on A5 adjustment.

    The overspeed fault is now in 60hz mode also. At times, I turn S1 to Start, starter engages for a split second then overspeed light comes on and will not crank. Push stop button, pull it back out and unit starts. I swapped S17 from the other unit just to be sure and no change.

  2. #12
    4 Star General Guyfang's Avatar
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    I do not think the over speed problem is specifically a 50 hertz, or 60 hertz mode problem. I think it was pure luck that the first time the faul happened, it was in 50 hertz mode.

    Try this. Swap the fault indicator panel. Then see if you continue to get an over speed fault.

  3. #13
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    I will try that in the morning.
    One thing that does not make sense to me, if power to the A5 - 18 excites the field for power generation, I get no power ever on that circuit but unit runs and makes power. Also, when the machine does start, I only have to bump the S1 for 1/2 a second. Any longer and the starter grinds but everything appears to operate normally once it is running.

    The other machine I have to hold the S1 for 5 to 10 seconds or it will shutdown. The starter does disengage while I hold S1 for the oil pressure and Hz to build.

  4. #14
    4 Star General Guyfang's Avatar
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    STOP!

    You our have a problem with your MPU. Pull it out. Check, clean and properly reinstall. If you need help, say something. Or read the TM. If the end is ground off, get a new one. Any time you get flywheel clash, the MPU is not working right.

  5. #15
    Chief and Indian 155mm's Avatar
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    Quote Originally Posted by 155mm View Post
    i think mpu voltages need to be lower than 3v, yours might be too close to flywheel.
    see above
    "Artillery Brings Dignity to What Would Otherwise Be Just A Vulgar Brawl"

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  7. #16
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    I could not find adjustment specs in the TM. Probably the TM I need won't open. What ACV should the MPU be set to?
    I checked both machines and they are both just above 3ACV like 3.3 or so.

  8. #17
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    I would remove and inspect, 2-3 vac
    "Artillery Brings Dignity to What Would Otherwise Be Just A Vulgar Brawl"

    "Happiness Is A Belt-Fed Weapon"

  9. #18
    Chief and Indian 155mm's Avatar
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  11. #19
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    Easy MPU set up is as follows. Line up the flywheel where a tooth is directly or as best you can, directly, in the center of the hole where the MPU is threaded into. With the MPU removed be sure it is as clean of small filings and anything metallic, thread it into the hole and for reference count the turns using a marks a lot or whatever works for you as you think or experience best. when it [mpu] bottoms onto the tooth, then back out1 to 1-1/2 turns, set the jamb nut crank and measure AC voltage, you already know ballpark range ur looking for, IN is more/higher output voltage, OUT is less or lower AC voltage.. this should settle the mag pick up issue and continue your problem solving efforts and you are assured this in no longer in your area of concern. As a side note you can measure the MPU voltage at the freq controller with the wires hooked up, the volt meter ur using wont burden the voltage enough to cause a significant difference to the controller modual... You don't have to try and hold your meter leads and all the mess it takes, with the wires set and anchored it is easy and you will get solid readings
    let us know, best of luck.. mac/mc

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  13. #20
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    Chesauto a bit more on the relationship between the MPU and its output voltage, on the speed controller you have several places for multiple adjustments, SPEED is one another is GAIN and might have another STABILITY or such.. when adjusted properly your engine should run very smooth, but to set it up long term, at speed 60 hz 1800 rpm turn the GAIN CW at a near point your engine should begin to move erratic, when you reach this condition, turn back CCW to GAIN until the engine runs smooth and steady. Gain adjustments' are derived from the MPU voltages being supplied to the controller, you can start to see the near symbiotic relationship between these signals.. When you finally set the gain be generous and over travel a bit, don't leave it right at the edge where your steady state becomes stable, these controllers and fuel temps play into the final settings. mac/mc

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