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Mig Wire Feeds as Soon as 12RC Suitcase is Powered Up

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  • jjohn76
    replied
    Nice!
    Last edited by jjohn76; 05-16-2020, 03:14 PM.

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  • Bushytails
    replied
    Glad to help!

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  • Houston IV
    replied
    Exchanged thew burnt MOSFET with new piece, test ran good. Next exchanged the $500.00 board and welded some 2" square tube for my patio, Thank you for the help

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  • Houston IV
    replied
    Originally posted by Bushytails View Post
    Don't change the mosfet without determining if the driver for it is bad too. That's a good way to end up changing things twice...
    Without knowledge of the failure root cause I am attempting to change the mosfet and determine the cause before i change the motor board. it was my opinion that the shipping back from the Grand Bahama Ship Yard caused the issue somehow there is a new scrape on the suitcase and the container was a jumbled mess when it came back. i will search out the driver and test as best as i can

    Thank You

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  • Bushytails
    replied
    Don't change the mosfet without determining if the driver for it is bad too. That's a good way to end up changing things twice...

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  • Houston IV
    replied
    Originally posted by jjohn76 View Post
    No problem. I had about half of the board schematic drawn out on my S-22P12 before I realized the schematic was available in an earlier operator manual. Mine was doing something similar, but.i haven't dug into it any further since picking up the schematic (my transistors were ok, so it's either the motor controller or feedback circuit). I can't remember if it is only the Extreme series or the later RC/VS models too, but remember at some point Miller went to potted boards, so replacement was the only option.
    I expect the new board this week. I found the MOSFET NPN 10A 100V and bought it for under $3.00 just to try to fix and use it as a back up if needed. I have an ESAB multi processor to Mig work but ave to lug the unit on board ship Suitcase is so much easier!

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  • jjohn76
    replied
    No problem. I had about half of the board schematic drawn out on my S-22P12 before I realized the schematic was available in an earlier operator manual. Mine was doing something similar, but.i haven't dug into it any further since picking up the schematic (my transistors were ok, so it's either the motor controller or feedback circuit). I can't remember if it is only the Extreme series or the later RC/VS models too, but remember at some point Miller went to potted boards, so replacement was the only option.

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  • Houston IV
    replied
    Originally posted by jjohn76 View Post
    The older Miller S-22P12 uses the same motor driver board as that machine, SG3254BN, so you may be able to get close on the schematic if you look at the S-22P12 version C owner's manual (that's the last manual that actually showed the schematic. The motor is driven directly by the motor driver right next to it, somewhere in the low digit pins (been a while since I looked at the one waiting repair in my basement). If I remember right, that manual also listed the mosfet, which will give you an idea on the specs you need. Check the motor driver too. Pull the schematic and do a diode test across the output. The S-22P12 had both outputs linked together to effectively drive the mosfet.
    jjohn,Thank you for your valuable insight

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  • Aeronca41
    replied
    Originally posted by jjohn76 View Post
    The older Miller S-22P12 uses the same motor driver board as that machine, SG3254BN, so you may be able to get close on the schematic if you look at the S-22P12 version C owner's manual (that's the last manual that actually showed the schematic. The motor is driven directly by the motor driver right next to it, somewhere in the low digit pins (been a while since I looked at the one waiting repair in my basement). If I remember right, that manual also listed the mosfet, which will give you an idea on the specs you need. Check the motor driver too. Pull the schematic and do a diode test across the output. The S-22P12 had both outputs linked together to effectively drive the mosfet.
    Jjohn, thanks for that info. I have an S-22P12 to go with my TB 280NT that I don't use much, but it's nice to know where to find a schematic for the motor board if I ever need it. Really appreciate your knowledge sharing here! Wish I had known that earlier--I might have been able to offer a free replacement MOSFET if I could find it. I have a pile of new surplus MOSFETS in the basement in their original tubes. Unfortunately, they are not yet indexed so I don't know what I have, but could have taken a look. Since he has the new board on order, not much help now--and I don't know how long it would take me to find out if I have anything that would work.

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  • Aeronca41
    replied
    Originally posted by Bushytails View Post
    Looking for the largest transistor near the problem area is a surprisingly reliable strategy.
    ...And one that has worked on more stuff than I can count in my 50+ years fixing stuff! One of my favorites. Almost as good as the pocket "tweaker" screwdriver for tapping tubes back in the day!

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  • jjohn76
    replied
    The older Miller S-22P12 uses the same motor driver board as that machine, SG3254BN, so you may be able to get close on the schematic if you look at the S-22P12 version C owner's manual (that's the last manual that actually showed the schematic. The motor is driven directly by the motor driver right next to it, somewhere in the low digit pins (been a while since I looked at the one waiting repair in my basement). If I remember right, that manual also listed the mosfet, which will give you an idea on the specs you need. Check the motor driver too. Pull the schematic and do a diode test across the output. The S-22P12 had both outputs linked together to effectively drive the mosfet.

    Leave a comment:


  • Bushytails
    replied
    Looking for the largest transistor near the problem area is a surprisingly reliable strategy.

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  • Aeronca41
    replied
    Maybe they had to do an update because the FETs burned up.

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  • Houston IV
    replied
    if I did send it out (was told it could be up to $500.00,) it would be the old style. Miller updated the board so I ordered it today

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  • Aeronca41
    replied
    No way to tell what the part number was--pretty thoroughly baked. I suspect a board repair co. would want a couple of hundred bucks to fix it, and that is often hit and miss. Irritating!

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