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Thread: Apple A2M6021X Monitor Repair.

  1. #1

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    Apple A2M6021X Monitor Repair.

    Fix this a few weeks back and been meaning to write up a quick repair log.
    This is the 240 volt version of Apple's colour composite monitor which is NTSC 50htz. This monitor will only work with Apple IIe Platinum's with the NTSC International motherboards which have a specially clock to NTSC 50htz. The American ones are 60htz so these are special to our region. My 240 volt Apple IIc also works in colour with this monitor. It will not work with the PAL adapter.

    I bought the monitor from Ebay knowing it was faulty with the hope to get it going considering how hard these monitors are getting to find now I thought I'd take the punt.
    The seller tried selling it for $300 BIN! $300 for a faulty monitor? tell him he's dreaming! Naturally after a few weeks it went up for auction and I got it for $120 bucks and thanks to @furballx and @WOKA it made the trip up north into my greasy hands.

    On first turning it on it made a ear piercing scream...ok not good I immediately thought shit bad Flyback Pulling the monitor apart to my horror there was a wire hanging down off the neck board (focus) and I could see straight away somebody had tried a gunshot repair. All caps had been replaced and a bunch of resistors and diodes too.
    Don't you hate when you buy something listed as "oh it just stopped working" only to find out it's been messed with.....shame that wasn't in the listing. What makes matters worse is there is no information or schematics available for this monitor anywhere!

    Taking the back off I turned the monitor on and managed to pinpoint the squeal which was coming from the little transformer which is part of the switch mode power supply. The switch mode supply's the B+ which should be sitting around 115 volts however it was only around 75. After talking to @Jomac he suggest there could be a short in the EHT. Without any way of testing the EHT I removed it to see if the B+ would jump back up to where it should be.

    Sadly it didn't but I more confidant that the flyback was ok. I decided to focus my attention on the switch mode section where a number of resistors had been replaced.
    Problems.jpg

    Pulling the back off two problems already, the convergence rings have been misaligned and the bigger issue is who ever reassembled the chassis fed the two wires under the shroud. One of the wires insulation was stripped back and touching the shroud grounding it.
    Turning it on again I pinpointed the squeal was indeed coming from the switch mode transformer.
    switch mode bad resistor.jpg
    Doing some measuring with the multi meter the two diode circled in red were shorted. Seeing as the monitor had been fiddled with I started pulling up the resistors which had been changed. Pulling up the 27 ohm resistor @R504 circled in black the diodes read correctly. Without a schematic it all I could do guesstimate the value based on other schematics I found using the STR40090 regulator. all I know for sure is it should be in the Kohm range not ohm!
    IMAG0039.jpg
    All I had was a pair of 22Kohm 2 watt resistors tied them in series to make 44k. We now have a nice 115v on the B+
    IMAG0038.jpg
    Suicide test setup!
    IMAG0012.jpg
    No squeal and now I have something on the screen even if it is vertical collapse.
    IMAG0018.jpg
    I found out about the 3 way service switch on an Apple forum. For normal operation this switch needs to be set to the left position(opposite to in pic), you'll get the vertical collapse in the center.

    At this point if I turn up the high voltage on the EHT I can see scan lines however no picture from my Apple IIe, all horizontal, vertical and sync adjustments work however nothing from the front panel does, brightness, contrast colour etc.
    I believe this is the original problem the monitor had before the previous owner decided to take the gunshot approach.
    The monitor uses a single video NTSC chroma processor chip TA7644BP. Probing around the IC with a scope I wasn't getting anything from the outputs.
    IMAG0025.jpgIMAG0026.jpg
    Ordered a chip from Ebay and popped it in.
    IMAG0042.jpg
    Realigned the convergence rings and fired her up.
    IMAG0031.jpg
    Success.
    IMAG0034.jpgIMAG0036.jpg
    Some fine tuning.
    IMAG0029.jpg
    Oh and this is what the picture looks like with the service switch to the right....

    IMAG0043.jpgIMAG0044.jpgIMAG0045.jpgIMAG0046.jpg
    A few reassembly pics
    IMAG0048.jpg
    And done. Monitor has been working flawlessly and the picture is magnificent.
    Big thanks to the AA Member who's sending me up a smokey A2M6021x monitor so I can get the correct values on the resistors. I'll update the thread when I find out.
    Lastly I'm really surprised on the lack of information out there. A lot of people seem more interested in whacking LCD's in these cases than fixing them.

    CRT's rule!

  2. #2

    Join Date
    Oct 2005
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    Quote Originally Posted by Arcade King View Post
    Fix this a few weeks back and been meaning to write up a quick repair log.
    This is the 240 volt version of Apple's colour composite monitor which is NTSC 50htz. This monitor will only work with Apple IIe Platinum's with the NTSC International motherboards which have a specially clock to NTSC 50htz. The American ones are 60htz so these are special to our region. My 240 volt Apple IIc also works in colour with this monitor. It will not work with the PAL adapter.

    I bought the monitor from Ebay knowing it was faulty with the hope to get it going considering how hard these monitors are getting to find now I thought I'd take the punt.
    The seller tried selling it for $300 BIN! $300 for a faulty monitor? tell him he's dreaming! Naturally after a few weeks it went up for auction and I got it for $120 bucks and thanks to @furballx and @WOKA it made the trip up north into my greasy hands.

    On first turning it on it made a ear piercing scream...ok not good I immediately thought shit bad Flyback Pulling the monitor apart to my horror there was a wire hanging down off the neck board (focus) and I could see straight away somebody had tried a gunshot repair. All caps had been replaced and a bunch of resistors and diodes too.
    Don't you hate when you buy something listed as "oh it just stopped working" only to find out it's been messed with.....shame that wasn't in the listing. What makes matters worse is there is no information or schematics available for this monitor anywhere!

    Taking the back off I turned the monitor on and managed to pinpoint the squeal which was coming from the little transformer which is part of the switch mode power supply. The switch mode supply's the B+ which should be sitting around 115 volts however it was only around 75. After talking to @Jomac he suggest there could be a short in the EHT. Without any way of testing the EHT I removed it to see if the B+ would jump back up to where it should be.

    Sadly it didn't but I more confidant that the flyback was ok. I decided to focus my attention on the switch mode section where a number of resistors had been replaced.
    https://www.aussiearcade.com/attachm...hmentid=144449

    Pulling the back off two problems already, the convergence rings have been misaligned and the bigger issue is who ever reassembled the chassis fed the two wires under the shroud. One of the wires insulation was stripped back and touching the shroud grounding it.
    Turning it on again I pinpointed the squeal was indeed coming from the switch mode transformer.
    https://www.aussiearcade.com/attachm...hmentid=144456
    Doing some measuring with the multi meter the two diode circled in red were shorted. Seeing as the monitor had been fiddled with I started pulling up the resistors which had been changed. Pulling up the 27 ohm resistor @R504 circled in black the diodes read correctly. Without a schematic it all I could do guesstimate the value based on other schematics I found using the STR40090 regulator. all I know for sure is it should be in the Kohm range not ohm!
    https://www.aussiearcade.com/attachm...hmentid=144457
    All I had was a pair of 22Kohm 2 watt resistors tied them in series to make 44k. We now have a nice 115v on the B+
    https://www.aussiearcade.com/attachm...hmentid=144458
    Suicide test setup!
    https://www.aussiearcade.com/attachm...hmentid=144461
    No squeal and now I have something on the screen even if it is vertical collapse.
    https://www.aussiearcade.com/attachm...hmentid=144462
    I found out about the 3 way service switch on an Apple forum. For normal operation this switch needs to be set to the left position(opposite to in pic), you'll get the vertical collapse in the center.

    At this point if I turn up the high voltage on the EHT I can see scan lines however no picture from my Apple IIe, all horizontal, vertical and sync adjustments work however nothing from the front panel does, brightness, contrast colour etc.
    I believe this is the original problem the monitor had before the previous owner decided to take the gunshot approach.
    The monitor uses a single video NTSC chroma processor chip TA7644BP. Probing around the IC with a scope I wasn't getting anything from the outputs.
    https://www.aussiearcade.com/attachm...hmentid=144466https://www.aussiearcade.com/attachm...hmentid=144467
    Ordered a chip from Ebay and popped it in.
    https://www.aussiearcade.com/attachm...hmentid=144468
    Realigned the convergence rings and fired her up.
    https://www.aussiearcade.com/attachm...hmentid=144469
    Success.
    https://www.aussiearcade.com/attachm...hmentid=144470https://www.aussiearcade.com/attachm...hmentid=144471
    Some fine tuning.
    https://www.aussiearcade.com/attachm...hmentid=144477
    Oh and this is what the picture looks like with the service switch to the right....

    https://www.aussiearcade.com/attachm...hmentid=144472https://www.aussiearcade.com/attachm...hmentid=144473https://www.aussiearcade.com/attachm...hmentid=144474https://www.aussiearcade.com/attachm...hmentid=144475
    A few reassembly pics
    https://www.aussiearcade.com/attachm...hmentid=144476
    And done. Monitor has been working flawlessly and the picture is magnificent.
    Big thanks to the AA Member who's sending me up a smokey A2M6021x monitor so I can get the correct values on the resistors. I'll update the thread when I find out.
    Lastly I'm really surprised on the lack of information out there. A lot of people seem more interested in whacking LCD's in these cases than fixing them.

    CRT's rule!
    test

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