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Apple A2M6021X Monitor Repair.

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  • #31
    Ok. with fly back transformer not installed turned down the B+ to 115.8v. then put the transformer back in and I get 0.578v. looked for leaking caps, the look fine took a couple out and tested ESR and they seem with in spec.

    So I guessing Fly back transformer. bugger will need to try and fine one and give it ago. It's a nice looking monitor the picture on yours looks awesome.

    Thanks so much for your write up on yours. I could fine anything on the inter-web about them.

    regards

    Vernon
    Attached Files

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    • #32
      Is the HOT transistor shorted?
      It's a shame I never got my hands on a spare monitor even for parts to verify etc would have helped heaps. Still spewing getting screwed over that.

      - - - Updated - - -

      Originally posted by palindrome View Post
      I installed the flyback but no go. There seems to be no load at all ( 125v @ b+ ) and buzzing is coming from the switch mode & possibly the new flyback as well.

      Removed flyback, installed load at b+ and buzzing stopped as expected. So I am not sure if the replacement flyback is incorrect or if there is another problem with the chassis. Original flyback might still be OK!

      Time to take a step back from this and think about what to do next.


      Were you able to solve your issue?
      How did you go with yours [MENTION=8115]palindrome [/mention]? where did you get your EHT from? I might order one just to confirm the alternative works.

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      • #33
        Do you mean the D1651 next to the Flyback.? I took that out and tested it for shorts it seemed ok.?

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        • #34
          No. Never got mine working. It's virtually impossible to find any reliable info on the above Flyback.

          The chassis is Hitatchi. The Flyback was also used in the A2M2056 which is discontinued, there's an ASTI replacement as well which is also discontinued.

          https://encompass.com/item/203860/Hitachi/2434742/

          I got my EHT from ebay. The fcc 1415-XL I believe was the recommended part wasn't it ? . But it's either not the correct one or mine was faulty or something else is wrong with the monitor.

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          • #35
            I just realized that I have a Apple Color Composite A2M6021X like your as well. I found it in the shed when looking for something else. I'll pulled the back off and take some readings and measure the Flyback connections and compare it with the A2M6020X they look almost identical inside. Well I'm at it I'll measure the B+ etc.

            It must go with one of my Apple IIe or Platinum. I lost track

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            • #36
              I've decided to convert this monitor to NTSC 60htz and ordered the colour burst crystal to do the job which means pulling this monitor down again.
              If you guys want to send your EHT's to me to test I'd be happy to do so while the things apart.
              I'm also going to put that 22 ohm resistor back in and see if it holds up, I'm kind of reluctant considering its been working great but apparently it was the correct value.

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              • #37
                I don't have the monitor anymore but I still have the original flyback.

                Not sure if it's much use to you.

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                • #38
                  Originally posted by palindrome View Post
                  I don't have the monitor anymore but I still have the original flyback.

                  Not sure if it's much use to you.
                  I'll grab it mate if you don't mind.

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                  • #39
                    Seems to be a popular issue with this model of screen as I too have squealing CRT.

                    This is my first real monitor repair other than changing caps etc so I wouldn't mind some advise.

                    Originally when I turned on the monitor I got no output and just the horrible squeal. Checking B+ I was getting 0v. I've then found the D1651 transistor was shorted. After remove it I rechecked the B+ and I'm now getting around 120V and the squeal.

                    I've got a replacement D1651 but I'm not sure if I should be looking for another fault that caused the original D1651 to fail or just replace and retry?

                    Cheers,
                    Danny

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                    • #40
                      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.

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                      • #41
                        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

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                        Sent from my iPhone using Aussie Arcade

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

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                          • #43
                            Finally got around to doing some work on my A2M6021x
                            Firstly [MENTION=14297]palindrome[/MENTION] 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.
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                            This is done by changing the 3.562456 mhz colour burst crystal to 3.579545mhz.
                            There's a very useful document I found HERE
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                            I also changed R504 back to 27ohm. Jaycar only had 5 watt
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                            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.

                            Click image for larger version

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                            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; 5th October 2019, 01:36 PM.

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                            • #44
                              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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