AppleColor composite monitor problem

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AppleColor composite monitor problem

I just received an AppleColor composite monitor, model A2M6020, and it has a little problem: everything displays as purple.

Well, it can do blue and orange as well. But 80 column text? Purple. White lines? Purple.

The tint, color, and "white only" button on the front of the monitor have no visible effect on the display.

My guess is that the green electron gun is kaput and that there's no reasonable way to repair it, and I should probably send it back. Opinions?

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Re: AppleColor composite monitor problem

Test you monitor with a different video source (DVD, Camera, VHS) and see if the problem goes away. If the problem remains, return the monitor.

CRTs are a real pain to ship. The last one that I shipped arrived with the neck broken off.

I got lucky over the holiday. Sears had a 19" Samsung LED HDTV on clearance for $129.00. It looks strange on top of the IIe but it does the job and I have a TV to watch when the Apple is sleeping.

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Re: AppleColor composite monitor problem

The problem of "no green" is the same regardless of the video source

I opened up the monitor this morning. Of course I have no experience in analog electronics, nor any documentation or troubleshooting info, but what the heck.

Among the many adjustments were three labeled "G BIAS", "R BIAS", and "B BIAS". Tweaking the B BIAS made the screen background a nice blue color (text was still purple, mind you). Doing the same to the R BIAS made the screen background red.

Adjusting the G BIAS, though, made no visual difference in the screen. So the green electron gun ain't firing. The question is whether this is a problem in the monitor circuitry which could be diagnosed and fixed, or whether it's a CRT problem in which case the monitor is junk.

Any opinions?

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Re: AppleColor composite monitor problem

You probably have an open circuit on the CRT controller. I had this same problem on a IIgs AppleColor RGB monitor, and I was able to fix it. Get the schematic (if you can find one) and test the transistor that controls the green signal.

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Re: AppleColor composite monitor problem

"get a schematic." That's the hard part…

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Re: AppleColor composite monitor problem

Did you buy this recently? Did it work before shipping? If so, file an insurance claim before time runs out.

The schematic is a must have for this type of trouble shooting. The schematic might be on the web along with troubleshooting hints for common problems.

You might get lucky with a DC volt meter if there is a simple biasing problem. Otherwise, you will need an oscilloscope to trace the signals going to the grids of the CRT.

Can you see the three cathodes glowing on the back of the neck?

Can you locate a part number on the boob tube? If you can, plug this number into a search engine and see if you can find a pinout for the neck.

Swap the red and green gun wires. You will probably have to swap both the cathode and grid leads. This will tell you if the problem is related to the CRT or the driver circuit. If you start seeing green, then the CRT is good. Most people will not be comfortable doing this experiment. This is why I said you need a scope.

Sorry but there is no easily way to troubleshoot this. Vacuum tubes were so much easier to deal with... If you did not own a tube tester, then you just swapped tubes until the set worked. Or you brought the bunch to Radio Shack for testing. I really am a dinosaur Smile

PLEASE NOTE: You will see a fat single wire going to the front of the CRT (top or side), that is the high voltage B+ line. DO NOT go near it while the power is on. DO NOT even go near the +B drive circuitry while the power is on. Even with the power off, you can get the shock that you will never forget. I am speaking from experience!!

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Re: AppleColor composite monitor problem

Them high voltage wires are loads of fun! They really mess with your ability to keep track of time and give you mega-strength!

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Re: AppleColor composite monitor problem

<< BIG SNIP >>

PLEASE NOTE: You will see a fat single wire going to the front of the CRT (top or side), that is the high voltage B+ line. DO NOT go near it while the power is on. DO NOT even go near the +B drive circuitry while the power is on. Even with the power off, you can get the shock that you will never forget. I am speaking from experience!!

I will REITERATE, High Voltage!!!!

A CRT Can Have Lethal Voltage even MONTHS after it was powered on... If some Reports can be believed..

There is conflicting Information on how dangerous this is, so I will leave you some links to look at and decide..

http://www.ifixit.com/Answers/View/197/How+dangerous+is+working+on+a+CRT+display
----> http://www.peachpit.com/articles/article.aspx?p=759704&seqNum=2

http://lowendmac.com/tech/crt_danger.html

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Re: AppleColor composite monitor problem

The monitor showed the problem before I bought it, but the seller and I thought it could be adjusted out. I have already received a full refund from the seller who told me not to bother shipping it back.

I have neither an oscilloscope nor the expertise to diagnose the problem myself. I have, however, received a shock from a flyback transformer before and yes, It's a bracing experience!

A local TV repair shop is looking at it, and I have my fingers crossed.

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Re: AppleColor composite monitor problem

Here is a little trick from the dinosaur.

An NE2 neon bulb taped to the end of a pencil can be used to check for the presents of high voltage on the B+ line. Place the bulb near the HV connector on the CRT and it should glow. If you hold it near the flyback it should glow.

Use to do this with old TVs where the HV was 150,000 to 200,000. It should also work with smaller monitors but the bulb will be dimmer.

This is a crude way to test the high voltage rectifier but it is cheaper than buying a high voltage probe.

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I know this is an old post

I know this is an old post But I am looking for the schematics for the Apple color Monitor A2M6020 as well. I cant find anything on the internet which is odd as this was a popular monitor. Anyone have an documentation on this or the other color composite monitors ( A2m4043 , A2M2056 )

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Verault wrote:I know this is
Verault wrote:

I know this is an old post But I am looking for the schematics for the Apple color Monitor A2M6020 as well. I cant find anything on the internet which is odd as this was a popular monitor. Anyone have an documentation on this or the other color composite monitors ( A2m4043 , A2M2056 )

 

I can but look. This is extremely outdated information, but, they were once available:

 

 

Schematic for Apple monitor Model A2M2056 and same for other Apple monitors; meter for Sencore CR168 CRT tester. Contact Steve Baker, 164 River Road, Hackettstown, NJ, (201) 927-0949.

 

He may still be alive. IDK. 

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Sure I can contact him but
Sure I can contact him but who is he jus so I have some background and dont come across as a crazy person. Thanks.
 
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And who is Steve Baker ?

And who is Steve Baker ?

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Verault wrote:And who is
Verault wrote:

And who is Steve Baker ?

Those contact details were from ~1986. Hence, I say, IDK u they are valid, and IDR if this si the same Steve Baker who worked for Atarisoft, or not. 

 

The point here, is thst they existed, and likely still exist, as they were available for purchase. 

 

The main issue with Apple, is that--even to service sources--they didn't provide schematics. Their policy was 'replace the entire board', not 'do component level repairs'. Thus, unlike say, Franklin, Atari or CBM manuals, they didn't include component-level schematics with their service manuals. I can provide at least three service manuals for these displays, but none of them have a proper schematic. You pretty much need to know what to look for, and have a general understanding of CRT repair to work on them. With tose, there is nothing magical or alien happening in them that typically requires a schematic, which is likely why there aren't any in the archives. 

 

In that regard, if you can detail the issues on the CRTs that are dead, we may be able to direct you on how to repair some of them. 

 

Do you have appropriate equipment (e.g. flyback discharge wands, and electricaician's gloves), to work on these? If you do not, then please, please, invest in the correct tools first, never try to work on a CRT without proper ischarging using a real diacharge wand. Even with the right tools, with my bad heart, I worry every time I start to work on one of these beasties. 

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Sure I have repaired many

Sure I have repaired many CRT Monitors over the years. I am not an expert by any means but Im not novice to CRT repair either.  Most of them have been The apple II monitor A2M2010 and Monitor III monitors A3M0039. Both have detailed schematics available online. They also both have SAMS computer facts repair manuals with additional schematics and circuit diagrams. 

 

Again I wasnt here to ask what to do with a dead monitor; I just have 3 of these color composite monitors that need service and I cant find any schematics or information online. I was hoping somone here has one or documents they would be willing to share.

 

 

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Verault wrote:Sure I have
Verault wrote:

Sure I have repaired many CRT Monitors over the years. I am not an expert by any means but Im not novice to CRT repair either.  Most of them have been The apple II monitor A2M2010 and Monitor III monitors A3M0039. Both have detailed schematics available online. They also both have SAMS computer facts repair manuals with additional schematics and circuit diagrams. 

 

A

 

What problems does each have? List the issues for each, in turn, and we may be able to provide solutions. 

 

Also, if they are this version, mine is missing the little door that covers the controls, and I could use a spare off of one:

 

I have the Apple service manual that covers it, but not circuit schematics. If for some reason you lack this, let me know and I will provide it. 

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One of mine that has a

One of mine that has a problem is the same as the one in your picture. An Apple Color composite IIe  model A2M2056. Mine is also missing the front cover.

 

The Problem with this monitor is the the Crt illuminates with no image (brightness and contrast work to vary the brigthness and intensity) and of course the heater is glowing. No image to the screen at all.

 

 

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Verault wrote:One of mine
Verault wrote:

One of mine that has a problem is the same as the one in your picture. An Apple Color composite IIe  model A2M2056. Mine is also missing the front cover.

 

The Problem with this monitor is the the Crt illuminates with no image (brightness and contrast work to vary the brigthness and intensity) and of course the heater is glowing. No image to the screen at all.

 

You have a raster, but no video? Have you taken that one apart enough to check the basic connections from the PCB and the composite RCA connection?

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Timelord wrote:Verault wrote
Timelord wrote:
Verault wrote:

One of mine that has a problem is the same as the one in your picture. An Apple Color composite IIe  model A2M2056. Mine is also missing the front cover.

 

The Problem with this monitor is the the Crt illuminates with no image (brightness and contrast work to vary the brigthness and intensity) and of course the heater is glowing.

Yes I have. IT used to work now it doesnt.

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AppleColor schematic?

Did anyone ever find a copy of a schematic for the AppleColor composite monitor?  These seem to be unobtainable.  I have one I'm trying to bring back to life.

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