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Thread: Apple A2M6021X Monitor Repair.

  1. #41
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    Quote Originally Posted by Arcade King View Post
    I'd be looking for any open resistors, test your diodes and yoke then power it on.
    Chances are if you HOT blows again you got a bad EHT.
    Just out of curiosity can you measure R504, interested to see what yours reads.
    Thanks.

    Re r504, Itís all back together and I couldnít quite reach it but it looks like 27 ohms if I have the color codes right

    IMG_5454.JPG


    Sent from my iPhone using Aussie Arcade

  2. #42
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    Thanks mate that's 2 people who've confirmed it.

  3. #43
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    Finally got around to doing some work on my A2M6021x
    Firstly @palindrome the EHT you sent was bad I pulled mine out and did a quick check with the multimeter between the pins to see if there was any noticeable differences 6 being ground. Unfortunately There was a short between pin 5 and 6 (1.3 ohm) which wasn't present on my Flyback. I tried it in the monitor anyway and got the squeal of death.

    Secondly I wanted to turn this monitor into full 60htz NTSC from 50htz NTSC. The only other 50hz machine I have is my Apple IIc which has its own green monitor and a special PAL adapter.
    IMG_20191004_084401.jpg
    This is done by changing the 3.562456 mhz colour burst crystal to 3.579545mhz.
    There's a very useful document I found HERE
    AppleColor_Composite_Monitor_specifications_2.jpg

    I also changed R504 back to 27ohm. Jaycar only had 5 watt
    IMG_20191004_101019.jpg
    I also added in that black ground wire I removed thinking it was a bodge but now confirmed factory although its made no difference what so ever.

    IMG_20191004_184749.jpg
    Swapped out my NTSC International motherboard for the modified 60hz one and... beautiful picture.
    In conclusion I have no idea why they bothered with 50hz NTSC. We now know the 50hz IOU was needed for the PAL Apple 2's with the extra circuity and 4.433618 Mhz crystal to output the PAL signal and older machines which had the PAL card in slot 7, however the A2M6021x like the Apple IIe Platinum with the International NTSC motherboard is unique with its 50/60htz IOU. Without this specific A2m6021x 50htz monitor you would need a PAL card to get colour on a TV or composite colour monitor like a Commodore 1084s otherwise as our long journey has shown you need to modify the motherboads crystal to 14.31818 MHz. I've now got a crystal tester so I'll update this thread eventually with the 50mhz crystal value.

    Thanks to everybody who has contributed to the discussion. It was a fun and frustrating learning experience.
    Last edited by Arcade King; 1 Week Ago at 03:36 PM.

  4. #44
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    Awesome work and research. Yeah I knew it, the B+ was virtually 0 volts with that EHT installed, that can’t be good for the power supply either. Connecting a dummy load ( 240v globe ) with the EHT removed confirmed it for me but this is more confirmation.

    One of the last things I’d like to confirm is if my original IOU is indeed faulty. Still looking around for a replacement. Since you have a IIc motherboard, the IOU in it should be socketed as well as most
    of the other main chips. I could loan it to you for you to test in the IIc.

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