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Thread: HELP with w440a montarbo

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    HELP with w440a montarbo

    hi i buy this montarbo w440a

    when i check there is no power i open the back of the speaker and check board

    i find many burned component i want to know their ref


    those are photo

    Click image for larger version. 

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ID:	51427Click image for larger version. 

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    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by tiesto23 View Post
    hi i buy this montarbo w440a

    when i check there is no power i open the back of the speaker and check board

    i find many burned component i want to know their ref


    those are photo

    Click image for larger version. 

Name:	1.jpg 
Views:	38 
Size:	4.51 MB 
ID:	51427Click image for larger version. 

Name:	2.jpg 
Views:	35 
Size:	4.06 MB 
ID:	51428
    Schematic:
    Attached Files Attached Files

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    Juan Manuel Fahey

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    Quote Originally Posted by J M Fahey View Post
    Schematic:

    can you help me identify this exact part on the schematic

    the borad i have is damaged






    thnx

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    Last edited by tiesto23; 12-08-2018 at 12:28 AM.

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    Supporting Member The Dude's Avatar
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    That's going to be a quite extensive repair. You've got several burnt resistors, which means something shorted. Aside from that, there's the burnt board and all the burnt traces to clean up and rebuild. Then, you'll have to find the root cause or shorted device(s). If you're not an experienced tech, I wouldn't event try it. You'll have to trace out everything on the schematic since they didn't see fit to silk screen the board with designation numbers. You're probably better off getting new board(s) or a new amp module. It's probably cheaper to just replace even for an experienced tech- lots of time and parts.

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    Quote Originally Posted by The Dude View Post
    That's going to be a quite extensive repair. You've got several burnt resistors, which means something shorted. Aside from that, there's the burnt board and all the burnt traces to clean up and rebuild. Then, you'll have to find the root cause or shorted device(s). If you're not an experienced tech, I wouldn't event try it. You'll have to trace out everything on the schematic since they didn't see fit to silk screen the board with designation numbers. You're probably better off getting new board(s) or a new amp module. It's probably cheaper to just replace even for an experienced tech- lots of time and parts.


    from my side its not problem of money or time i want to fix it

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    Can you read schematics? If not, I don't think you will be able to fix it. You are going to have to trace out the schematic connections to fix and verify the burnt traces. It's not something that can be done without the unit, so no one here can tell you what to do without access to the burnt board.
    If you can read schematics, the board is the one called 440F on the schematic. It is 2 circuits that are mirror images (high and low), plus the 15V +&- supplies. So you can look at the good side to find the value of the bad side.
    Aside from the parts you circled, there is a cap bulging and ready to burst by the ribbon connector. Also, on the other board you had a picture of, there is a burnt resistor. So, if you fix this board, the other board may be bad also. And if the amps are bad, the speakers could be blown too.
    So check the speakers before anything.

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

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    Quote Originally Posted by g1 View Post
    Can you read schematics? If not, I don't think you will be able to fix it. You are going to have to trace out the schematic connections to fix and verify the burnt traces. It's not something that can be done without the unit, so no one here can tell you what to do without access to the burnt board.
    If you can read schematics, the board is the one called 440F on the schematic. It is 2 circuits that are mirror images (high and low), plus the 15V +&- supplies. So you can look at the good side to find the value of the bad side.
    Aside from the parts you circled, there is a cap bulging and ready to burst by the ribbon connector. Also, on the other board you had a picture of, there is a burnt resistor. So, if you fix this board, the other board may be bad also. And if the amps are bad, the speakers could be blown too.
    So check the speakers before anything.

    i check the speaker and working good with other externel amp

    i identify some part

    but the problem is on burned sport totaly blind sport for me

    i hope someone have same speaker as i have so it will be very easy

    i found picture on the web same ( not fully detailed) as my amp so it help me to identify some component

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

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    Quote Originally Posted by g1 View Post
    Maybe same amp but not same pictures of the same section.

    nosaj

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    Last edited by nosaj; 12-08-2018 at 02:55 AM.
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    Quote Originally Posted by g1 View Post
    yes those picutre are same as my speacker system

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    Quote Originally Posted by nosaj View Post
    Maybe same amp but not same pictures of the same section.

    nosaj
    this is same section

    of my burned board





    compare the picture

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    Lifetime Member Enzo's Avatar
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    Upper right just outside the red circle is an MJE15032 transistor. It is almost certainly dead. Chances are the other similar transistors may be dead.

    Identify and replace at least the five small transistors in the circle. Four are in sight, the fifth went to the three solder pads near the top of the ring. Across the center of the ring, the two diodes on the right look like common types. The two resistors next to them appear to be 47 ohms. The two resistors on the left appear to be 22 ohm. Resistor next to the missing transistor, maybe 100 ohms?

    Top of the picture just outside the ring, a burnt resistor between the orange cap and the heat sink transistor. No idea. Upper left corner of board, a lonesome transistor, looks shaky to me. Frosty solder.

    All that damage pretty much guarantees that the heat sink transistors are damaged. And that in turn tells me the power transistors on the other board are damaged.

    This will not be easy even for an experienced professional.

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    Talking

    Quote Originally Posted by Enzo View Post
    Upper right just outside the red circle is an MJE15032 transistor. It is almost certainly dead. Chances are the other similar transistors may be dead.

    Identify and replace at least the five small transistors in the circle. Four are in sight, the fifth went to the three solder pads near the top of the ring. Across the center of the ring, the two diodes on the right look like common types. The two resistors next to them appear to be 47 ohms. The two resistors on the left appear to be 22 ohm. Resistor next to the missing transistor, maybe 100 ohms?

    Top of the picture just outside the ring, a burnt resistor between the orange cap and the heat sink transistor. No idea. Upper left corner of board, a lonesome transistor, looks shaky to me. Frosty solder.

    All that damage pretty much guarantees that the heat sink transistors are damaged. And that in turn tells me the power transistors on the other board are damaged.

    This will not be easy even for an experienced professional.
    thnx alot

    mostly the part that you identify same as my identification

    for the MJE15032 there is trace of new solder i think it was changed recently ( but i will whange then all and install custom heatsink)

    yes right there is 2 power transistor without leg ( totaly burned)

    i think WWII was made on this amp ...

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    What is your level of experience for repairs tiesto23 ?
    It will help us with our responses to know if you are a technician or hobbyist.

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

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    Quote Originally Posted by g1 View Post
    What is your level of experience for repairs tiesto23 ?
    It will help us with our responses to know if you are a technician or hobbyist.
    you can say both technicien and hobbyist

    you can say 5/10 mostly i m technicien of pc& laptops

    but asmy hobby is playing music and do some repair on instrument or iteam that i buy for myself

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    Quote Originally Posted by Enzo View Post
    Upper right just outside the red circle is an MJE15032 transistor. It is almost certainly dead. Chances are the other similar transistors may be dead.

    Identify and replace at least the five small transistors in the circle. Four are in sight, the fifth went to the three solder pads near the top of the ring. Across the center of the ring, the two diodes on the right look like common types. The two resistors next to them appear to be 47 ohms. The two resistors on the left appear to be 22 ohm. Resistor next to the missing transistor, maybe 100 ohms?

    Top of the picture just outside the ring, a burnt resistor between the orange cap and the heat sink transistor. No idea. Upper left corner of board, a lonesome transistor, looks shaky to me. Frosty solder.

    All that damage pretty much guarantees that the heat sink transistors are damaged. And that in turn tells me the power transistors on the other board are damaged.

    This will not be easy even for an experienced professional.

    after changing all burned part

    and doing some safe test on ac power entry before plug power cable

    result

    fuse blowout

    there is short in Ac power entry

    then test on transformer (55 v) short in entry and output

    test on power transistor 2 dead IRFP9240 & 2 dead IRFP240

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    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by tiesto23 View Post
    after changing all burned part

    and doing some safe test on ac power entry before plug power cable

    result

    fuse blowout

    there is short in Ac power entry

    then test on transformer (55 v) short in entry and output

    test on power transistor 2 dead IRFP9240 & 2 dead IRFP240
    1) you shouldn't have plugged it straight into Mains but used a lamp bulb limiter.
    Otherwise every time you turn it on "direct" you will damage more parts.

    2) replacing al visibly burnt parts is not enough, sadly many damaged parts "look new" , specially semiconductors, yet are very dead ... and damage others.

    So please first build (and use) the bulb limiter, a 40W to 75W filament bulb is suitable for this amp.

    I doubt the transformer is bad: windings , specially secondaries, normally read quite low.
    The proper way to check a power transformer is to plug primary into mains through bulb limiter, and see what happens with all secondaries disconnected and taped for safety.

    You have the main power amplifier schematic, verify board matches it, specially follow tracks from pad to pad , any missing (burnt off) track will make a mess so triple check all in the burnt area.

    Replace burnt parts and try amp ON again.

    In fact, use an even smaller 25W bulb, today we are not worried by low voltages but gross internal shorts, so let´s play it very safe.

    Montarbo power amps are "relatively" crude, simple designs ... which in this case is good.

    Still no speaker or any load attached .

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    Quote Originally Posted by J M Fahey View Post
    1) you shouldn't have plugged it straight into Mains but used a lamp bulb limiter.
    Otherwise every time you turn it on "direct" you will damage more parts.

    2) replacing al visibly burnt parts is not enough, sadly many damaged parts "look new" , specially semiconductors, yet are very dead ... and damage others.

    So please first build (and use) the bulb limiter, a 40W to 75W filament bulb is suitable for this amp.

    I doubt the transformer is bad: windings , specially secondaries, normally read quite low.
    The proper way to check a power transformer is to plug primary into mains through bulb limiter, and see what happens with all secondaries disconnected and taped for safety.

    You have the main power amplifier schematic, verify board matches it, specially follow tracks from pad to pad , any missing (burnt off) track will make a mess so triple check all in the burnt area.

    Replace burnt parts and try amp ON again.

    In fact, use an even smaller 25W bulb, today we are not worried by low voltages but gross internal shorts, so let´s play it very safe.

    Montarbo power amps are "relatively" crude, simple designs ... which in this case is good.

    Still no speaker or any load attached .


    hi i did not plug the speaker in power

    i say i do simple check in input and output of many part before plug in power

    there is short on transformer and i verify that when i plug the transformer alone = power short fuse blow out

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    Old Timer J M Fahey's Avatar
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    Ok, if you have a dead power amp and a dead transformer then you have nothing, not worth repairing it because it will cost more than buying a new one, and you have zero guarantee it will work anyway..

    I suggest plans B and C:

    b) remove all electronics , on the remaining backplate install 2 speakons and a suitable crossover.
    Drive it from any powered mixer or rackpower amp you have available.
    VERY popular here in Argentina, I see it all the time.

    c) get a plate amp which fits the current backplate or cut an aluminum rectangle, say 2 or 2.5 mm thick, of exact size to fit hole left by original Montarbo power unit, and mount yopur new power amp and supply there.
    A Class D amplifier + SMPS supply will be lighter and cooler than the original Montarbo .

    Google/EBay/Alibaba are your friends..

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    Quote Originally Posted by J M Fahey View Post
    Ok, if you have a dead power amp and a dead transformer then you have nothing, not worth repairing it because it will cost more than buying a new one, and you have zero guarantee it will work anyway..

    I suggest plans B and C:

    b) remove all electronics , on the remaining backplate install 2 speakons and a suitable crossover.
    Drive it from any powered mixer or rackpower amp you have available.
    VERY popular here in Argentina, I see it all the time.

    c) get a plate amp which fits the current backplate or cut an aluminum rectangle, say 2 or 2.5 mm thick, of exact size to fit hole left by original Montarbo power unit, and mount yopur new power amp and supply there.
    A Class D amplifier + SMPS supply will be lighter and cooler than the original Montarbo .

    Google/EBay/Alibaba are your friends..

    hi again i success to fix the amp and test it with other transormer with lower power it work fine without any distortion

    it cost 5 euro pieces

    but now the funny thing is the transformer


    any seg from your part , about Class D amp & smps supply

    thnx

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    Quote Originally Posted by tiesto23 View Post
    yes those picutre are same as my speacker system
    Thanx for sharing my article
    I rebuild lots of these amps. Unfortunately the damage on this board is extensive. I haven't seen one with so much damage.
    Yikes!!
    Its probably fixable.

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    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by tiesto23 View Post
    hi again i success to fix the amp and test it with other transormer with lower power it work fine without any distortion
    Good!!! Congratulations!!!
    but now the funny thing is the transformer
    Well, since you already fixed the amplifier, which is the hard part, now getting a replacement transformer is not such a big deal.

    If you find one same specs, perfect.

    If you find one with somewhat less voltage, no big deal.

    Say original one used 60V rails and the one you found (at low cost or pulled from a dead amplifier) gives you 55 or 50V rails ... when "measured" you´ll find less power output but when in actual use ... you won´t *hear* that much difference ... if at all.

    Not sure if you are repairing "just one" or you are a Tech with a continuous work flow; if so, you probably have your own "junkyard" with a couple dead amplifiers or powered mixers ... you can often reuse a power transformer pulled from these.

    Please post a couple pictures showing the full plate amplifier innards, I´m specially interested in how are power MosFets attached to heat sink.
    I always see the grey ribbon cable connecting PCB to them but nobody ever shows them.

    It will also be useful to see how/where is the current power transformer mounted and what free space you need for a new one.

    If you post core size measurements, I can estimate VA rating.

    The few I have seen (in smaller Montarbo cabinets) were conventional EI type, not sure about yours: is it EI type or a Toroid?
    Does it have any labels on it?

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    Quote Originally Posted by J M Fahey View Post
    Good!!! Congratulations!!!

    Well, since you already fixed the amplifier, which is the hard part, now getting a replacement transformer is not such a big deal.

    If you find one same specs, perfect.

    If you find one with somewhat less voltage, no big deal.

    Say original one used 60V rails and the one you found (at low cost or pulled from a dead amplifier) gives you 55 or 50V rails ... when "measured" you´ll find less power output but when in actual use ... you won´t *hear* that much difference ... if at all.

    Not sure if you are repairing "just one" or you are a Tech with a continuous work flow; if so, you probably have your own "junkyard" with a couple dead amplifiers or powered mixers ... you can often reuse a power transformer pulled from these.

    Please post a couple pictures showing the full plate amplifier innards, I´m specially interested in how are power MosFets attached to heat sink.
    I always see the grey ribbon cable connecting PCB to them but nobody ever shows them.

    It will also be useful to see how/where is the current power transformer mounted and what free space you need for a new one.

    If you post core size measurements, I can estimate VA rating.

    The few I have seen (in smaller Montarbo cabinets) were conventional EI type, not sure about yours: is it EI type or a Toroid?
    Does it have any labels on it?


    this original montarbo transformer is 55 V 0 55 V

    i cannot find like him on web or less one with less power and less size beacue you can see on picture its less space to put other one with +- few size difference

    [IMG][/IMG]




    [IMG][/IMG]

    [IMG][/IMG]

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    Old Timer J M Fahey's Avatar
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    Interesting: a sandwich/stacked board construcion to save space: one board carrying the MosFets and right against the heatsink, plus the driver/processor board "floating" over it, maybe 10/12mm - 1/2" above it on computer board type stacking insulators.

    The grey flat ribbon cable here helps servicing, you can "open the sandwich" and look/work inside without much trouble and with amp still working, not a bad idea at all.

    Thanks a lot

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    Last edited by J M Fahey; Today at 01:05 AM.
    Juan Manuel Fahey

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    You should/should have cleaned up and removed all of that burnt circuit board. It can become conductive when it burns.

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    Quote Originally Posted by The Dude View Post
    You should/should have cleaned up and removed all of that burnt circuit board. It can become conductive when it burns.
    just make sure if my work is good i allready clean with G-20 but still some places but i will remake all work

    maybe print a new pcb after scan this one & install new heatsink

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    Old Timer J M Fahey's Avatar
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    What the Dude says is that besides any "chemical" cleaning, you must scratch/sand/dremel out all carbon residue from tje board, because carbon is conductive and cause new shorts.

    In extreme cases where carbon goes all the way through the board to the other face, Techs have cut through and discarded a rectangular "window" in the PCB and replaced missing tracks with rigid wires "floating in the air".
    Yours is not *that* bad, but I mention this so you know CARBON IS YOUR ENEMY.

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