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Thread: Emerson ecm teardown

  1. #1
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    Emerson ecm teardown

    I have torn down an emerson 3/4 hp ecm and removed all the glue so I can inspect the board. My question is. Are these emerson motors with the ecm DC or AC? I keep hearing people say DC but apoun inspection of the motor driver it is an 3 phase ac igbt motor driver. I dont know much about motor drivers.

    Part number iram136-1060a. Also the eeprom and processor and EEPROM on these boards have hardware write protection.

    The processor is a TMS320F2802x

    The furnace acts like its turning on before complaining about motor not running. So I put oscilloscope on the 6 wires from the CPU that generate the frequency for the iram136 and they are silent. However I still see 2 way communication between the ecm board and the logic board in the furnace. This kinda tells me these thing may have some error counter lockout. Or maybe it even detect a bad motor and disabled it self. The programming is locked I think if you try to dump or modify anything the chip may erase

    in the pictures there is a broken thermistor and a missing capacitor on the spi enable lines. the thermistor was wirenutted together and i damaged the tiny cap.

    i figured i would post pictures anyways incase someone else want to see them

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  2. #2
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    And why did we do all this work?

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  4. #3
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    i was trying to find out why the motor would not run. im not replacing this motor with a 700 dollar motor. it will get a qwikswap v3 and a 240 3 speed psc motor. i got the furnace for free its a goodman hecf and there is no loss in tearing down something free. and i figure maybe someone would find something useful. i would find it useful to know the p/n of the thermistor thats missing. It seems like the processor on the ecu board is in working condition but does not attempt to start the motor. there may be a way to reset the board but probably not. they went out of their way to use components with security so im sure they use it.

    In other words, im bored lol

  5. #4
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    Ill accept that

  6. #5
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    It would have taken me more work to post all those pictures on here then to break down the motor. Lol that’s a lot of pictures.

  7. #6
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    Its a three phase motor and the module converts, rectify or whatever ya wanna call it to dc voltage. Controlled with pwm and if you look up the wave form of it I believe its square wave form. Really interesting

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  9. #7
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    Yes a three phase motor. The ac is rectified by a bridge rectifier and a smoothing cap. There may be a regulator to further regulate the voltage. The motor is then driven by waveforms developed by a set of power transistors and controlled by the processor.

    Not sure what value you would get out of reading the ROM contents without understanding what they mean. Disassembled code might be helpful.

    If you want to play around with this sort of thing I would check if TI has an eval board for that processor. They make very reasonably priced eval boards for their chips. If code is developed for it using Code Composer that is also free the last time I used it. You could then couple that to some power drive electronics and a motor and experiment.

  10. #8
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    What is the component missing from the board? Is it the ntc thermistor? If so why even attempt to dig into that board without replacing that thermistor? The board will NEVER function without it!
    "I think Quantum tunneling would work great... "

    "Call a technician for God's sake. Or we'll see you on the news or the Dark Side of the Moon."

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  12. #9
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    Quote Originally Posted by JayMan7 View Post
    What is the component missing from the board? Is it the ntc thermistor? If so why even attempt to dig into that board without replacing that thermistor? The board will NEVER function without it!
    I was about to point that out.

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  14. #10
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    Quote Originally Posted by Somerandom816 View Post
    I have torn down an emerson 3/4 hp ecm and removed all the glue so I can inspect the board. My question is. Are these emerson motors with the ecm DC or AC? I keep hearing people say DC but apoun inspection of the motor driver it is an 3 phase ac igbt motor driver. I dont know much about motor drivers.

    Part number iram136-1060a. Also the eeprom and processor and EEPROM on these boards have hardware write protection.

    The processor is a TMS320F2802x

    The furnace acts like its turning on before complaining about motor not running. So I put oscilloscope on the 6 wires from the CPU that generate the frequency for the iram136 and they are silent. However I still see 2 way communication between the ecm board and the logic board in the furnace. This kinda tells me these thing may have some error counter lockout. Or maybe it even detect a bad motor and disabled it self. The programming is locked I think if you try to dump or modify anything the chip may erase

    in the pictures there is a broken thermistor and a missing capacitor on the spi enable lines. the thermistor was wirenutted together and i damaged the tiny cap.

    i figured i would post pictures anyways incase someone else want to see them

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Views: 648
Size:  1.59 MBName:  20210226_200711.jpg
Views: 645
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Views: 647
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Views: 645
Size:  2.59 MBName:  20210227_100508.jpg
Views: 649
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Views: 647
Size:  2.76 MBName:  20210226_165107.jpg
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    You sound intelligent and I always said sometimes the easier shit boggles our genius minds.

    With that in mind,why didnt you just ohm out the motor?


    Sent from my iPhone using Tapatalk
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  16. #11
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    I'm gona see of I can get that Ntc thermistor replaced. I think with the thermistor jumped out like they had it those dc caps could exploded.

    Aparrently it was working with the thermistor jumped for a little bit. So far I have not found anything else wrong with the board. Its 2 way communication with the air handler board is still in tact. I almost wanna say it has some sort or error lockout in the ecm

  17. #12
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    Back in the days if there was enough leads on that blown thermistor, I would just jumper it out and solder it together. Then install the external kit we could get from Zebra. Or solder in a new component also available through Zebra at the time. Then the motor companies got smart as what we as techs were doing and decided to start adding potting to the circuit boards to impede any simple field repairs. The motor companies played it off that they were doing it to prevent water infiltration, but many of us with close relationships with the representatives of these manufactures were advised that it was to prevent us from making these repairs. Figure a total of upto $1000 was being taken out of their and furnace manufacturer's pockets whenever we made a simple field repair.

    In anycase, appreciate your pictures, but you are grossly late to the party. The ECM/Constant Torque motors have been around now for nearly 25 years or so nothing really new here.

    I still have a "cease and assist" letter from GE/Beloit from when I did exactly what you did back in the early 2000's. They did not like the fact that I and a friend downloaded the firmware and parameter settings and figured out how to re-write them on another module.

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  19. #13
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    The upgraded motor is the quick swap X1 conversion to psc on my end...lol..

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  21. #14
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    Quote Originally Posted by Unlimited1 View Post
    The upgraded motor is the quick swap X1 conversion to psc on my end...lol..
    True DAT!

  22. Likes Unlimited1 liked this post.

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