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Apple A2M6021X Monitor Repair.


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Unfortunately don't have one. So I'm going to have to shotgun the chassis and replace the main caps in the power supply.

 

Whilst the cap looks good and isn't leaking, the gas might be escaping from the bottom of the cap.

 

Research has revealed some other part numbers.

 

If you look at the silkscreening on the main board you'll see that the same chassis was used in 3 other Apple ii monitors.

 

Googling those model numbers, I come up with Hitachi 2434742.

 

Subsequent google searches come up with the following info.

 

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

https://encompass.com/model/HITA2M2056

 

Compatible Models: A2M2056

 

The monitor appears to have been made by Hitachi.

 

More google searches.

 

"NTEFC560 NTE Flyback Replaces Hitachi 2434741 1 pc"

"NTEFC560 APPLE COMPUTER REPL. FLYBACK"

 

https://www.ued.net/ued/viewItemAction.do?itemCode=HIP2434742

https://www.ued.net/ued/viewItemAction.do?itemCode=HIP2434741 <-- looks like this a substitute for 2434742

 

Going to look into the NTEFC560 further.

Edited by palindrome
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  • 2 weeks later...
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  • 3 weeks later...

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?

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  • 4 months later...

A2M6020X

 

Hi there,

 

My first post asking a question.

 

I have just been reading over your repair to your A2M6021X monitor and it got be keen to have a look at mine with is similar it's a A2M6021X and looks very close to yours inside.

 

I brought a Apple IIe off your local auction site that was working, And when I picked you the computer the guy gave me my monitor saying that it didn't work, So i thought why not worth the gamble.

 

I turned it on and it makes i high pitched noise and no picture, so then switch off to take the back off it and check the B+ voltage which there was no voltage. So after reading though your post I un-soldered the fly back transformer and tested it again and the voltage jump to 155V a little high i guessing but at least i now see voltage. Still has a hight pitched scream coming from the board.

 

Would this mean the flyback tramsformer is dead or would you suggested I look at another area on the board for perhaps a component failure.

 

It also has 1 bodge wire on the back of PCB.

 

Any suggestion would be greatly appreciated.

 

Vernon

 

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/attachment.php?attachmentid=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/attachment.php?attachmentid=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/attachment.php?attachmentid=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/attachment.php?attachmentid=144458

Suicide test setup!

https://www.aussiearcade.com/attachment.php?attachmentid=144461

No squeal and now I have something on the screen even if it is vertical collapse.

This was caused from the service switch being set in the middle position.

https://www.aussiearcade.com/attachment.php?attachmentid=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/attachment.php?attachmentid=144466https://www.aussiearcade.com/attachment.php?attachmentid=144467

Ordered a chip from Ebay and popped it in.

https://www.aussiearcade.com/attachment.php?attachmentid=144468

Realigned the convergence rings and fired her up.

https://www.aussiearcade.com/attachment.php?attachmentid=144469

Success.

https://www.aussiearcade.com/attachment.php?attachmentid=144470https://www.aussiearcade.com/attachment.php?attachmentid=144471

Some fine tuning.

https://www.aussiearcade.com/attachment.php?attachmentid=144477

Oh and this is what the picture looks like with the service switch to the right....

 

https://www.aussiearcade.com/attachment.php?attachmentid=144472https://www.aussiearcade.com/attachment.php?attachmentid=144473https://www.aussiearcade.com/attachment.php?attachmentid=144474https://www.aussiearcade.com/attachment.php?attachmentid=144475

A few reassembly pics

https://www.aussiearcade.com/attachment.php?attachmentid=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!

back.thumb.jpg.e924eb518f4f7856414cb327feb4b8a9.jpg

inside2.thumb.jpg.cb7ad7c106502a4ca8d5a8d50b5b8e29.jpg

switchmode.thumb.jpg.d2886ffd19b55f3af43839f6c9c4e8ac.jpg

flyback-removed.thumb.jpg.b2e5710d87dc9fca37fcf805e35dabb5.jpg

backPCB.thumb.jpg.838902ac144539af2252b91dcd404c65.jpg

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Ha i had the same wire on mine thinking it was some bodge I removed it but obviously its factory.

Its odd because its just a ground wire and removing it the two points were still grounded but they must have done it for some reason.

 

In your case id start by turning down that B+ to 115v see if you can feel any static on the screen. Squealing could also be caused by the sub horizontal hold pot out of adjustment. Check for leaking and bloated caps.

Worse case it will be the flyback.

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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

flyback.thumb.jpg.e75b00df5cda9cabfad0e03ba49eed6b.jpg

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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 - - -

 

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 @palindrome ? where did you get your EHT from? I might order one just to confirm the alternative works.

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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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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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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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  • 3 weeks later...

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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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, It’s all back together and I couldn’t quite reach it but it looks like 27 ohms if I have the color codes right

 

IMG_5454.thumb.JPG.51af68e942fd110d6df8aab47fd349a8.JPG

 

 

Sent from my iPhone using Aussie Arcade

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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.thumb.jpg.c14b5e4dcea40b1f713db80f97ba41a5.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.thumb.jpg.8c093a4098b60eea7d04fc27e82e5ac8.jpg

 

I also changed R504 back to 27ohm. Jaycar only had 5 watt

IMG_20191004_101019.thumb.jpg.de56e52eda51304a27b3151004a2d5ef.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.thumb.jpg.230a56efcfe1bad61c048258273095cd.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.

Edited by Arcade King
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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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  • 7 months later...

 

I just went through and re-capped one of these monitors overnight, thought I might put this here for future reference.

 

Capacitor List:

C390 - 50v, 47uf

C211 - 50v, 1uf

C135 - 50v, 1uf

C130 - 50v, 10uf

C102 - 16V, 100uf

C111 - 16v, 10uf

C203 - 50v, 0.47uf

C213 - 50v, 0.47uf

C309 - 35v, 470uf

C218 - 50v, 0.47uf

C138 - 25v, 1000uf

C209 - 16v, 100uf

C117 - 50v, 0.47uf

C136 - 16v, 1000uf

C120 - 50v, 0.47uf

C220 - 16v, 47uf

C305 - 35v, 470uf

C302 - 25v, 1000uf

C312 - 50v, 10uf

C310 - 35v, 22uf

C308 - 50v, 1uf

C161 - 25v, 47uf

C501 - 400v, 220uf

C502 - 160v, 1uf

C505 - 100v, 0.47uf

C503 - 50v, 1uf

C101 - 50v, 47uf

C509 - 160v, 220uf

C224 - 160v, 1uf

C201 - 50v, 1uf

C140 - 250v, 22uf

C908 - 250v, 1uf (Neckboard)

 

*Edited 05/06/2020 to update correct value of C101

Edited by nauseous
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I just went through and re-capped one of these monitors overnight, thought I might put this here for future reference.

 

Capacitor List:

C390 - 50v, 47uf

C211 - 50v, 1uf

C135 - 50v, 1uf

C130 - 50v, 10uf

C102 - 16V, 100uf

C111 - 16v, 10uf

C203 - 50v, 0.47uf

C213 - 50v, 0.47uf

C309 - 35v, 470uf

C218 - 50v, 0.47uf

C138 - 25v, 1000uf

C209 - 16v, 100uf

C117 - 50v, 0.47uf

C136 - 16v, 1000uf

C120 - 50v, 0.47uf

C220 - 16v, 47uf

C305 - 35v, 470uf

C302 - 25v, 1000uf

C312 - 50v, 10uf

C310 - 35v, 22uf

C308 - 50v, 1uf

C161 - 25v, 47uf

C501 - 400v, 220uf

C502 - 160v, 1uf

C505 - 100v, 0.47uf

C503 - 50v, 1uf

C101 - 50v, 1uf

C509 - 160v, 220uf

C224 - 160v, 1uf

C201 - 50v, 1uf

C140 - 250v, 22uf

C908 - 250v, 1uf (Neckboard)

 

How did it come up?

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Very similar to before replacing capacitors (was hoping this would have resolved fault - but clearly something more going on). But that's OK as at least all of the above are now ruled out. You can't really see in the photo but the monitor is showing output. APPLE II and the console prompt is visible but scrolling.

 

Just working on getting a complete list of symptoms at the moment. Some of the adjustment pots look to be dirty / stuck.

 

20200514_102856.thumb.jpg.111633854a6c48137a2f86f5877533eb.jpg

 

Would it make any difference driving this from a Apple IIe (currently testing with a Apple +) ?

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Switch does appear to orientated correctly.

 

Just spent a little bit more time and went over all the pots to get those stuck moving again. I can hear the monitor's EHT come on, but the screen just stays black. I guess it's time to double check the adjustment pots...

 

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Got a little further with this over the weekend. I am suspect that the TA7644BP is faulted. It looked dubious when I first opened the case.. The earth strap on the back of the monitor had disintegrated and made a mess of the chassis. Subsequently I cleaned the chassis and replaced earth strap (plus a few other components).

 

The picture on screen comes and goes at random, when it is visible the adjustments make no difference to the display (brightness, contrast, v/h hold, size).

 

Last night digging around on the internet I have found that the Samsung 20K20 chassis is almost identical to this model Apple. Same IC's, very similar internal wiring, even to the point it has a 3 way service switch. Mind you being a TV set it has extra circuitry for the tuner portion, but this is drawn separate to the actual CRT workings. I'm sure there will be subtle differences between this and the Apple monitor so use it purely as a guide to aid you in troubleshooting. I am doubtful that component labels/values match exactly.

 

Here is a link to the schematic https://elektrotanya.com/samsung_20k20_chassis_mtc_mtv207r.pdf/download.html

 

 

 

 

20200430_163415.thumb.jpg.c53e675ba46fa7a6a0f618a4800bc5a6.jpg 20200430_163740.thumb.jpg.bd126a64f844ac066e2d1000a1ae2a66.jpg 20k20.PNG.8bfc091550302553dad1531f88bc82f3.PNG

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