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Atari 800 Video Issues


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#1 Osxster OFFLINE  

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Posted Fri May 11, 2018 10:18 AM

Hello,

 

I just picked up an Atari 800 from EBay.  The thing seems to work mostly, however when I noticed that I first hooked it up to an S-Video to VGA adapter, the screen got very white, washed out.  At first it almost looked like it had no color.  I played with the POT adjustment and got a little more blue out of it, but it still doesn't look like my 130XE.  When I hook up the S-Video to a regular TV, I thought it looked better and was thinking the signal strength of the Atari 800 was over powering the S-Video to VGA adapter.  But upon further investigation, some of my Red isn't really coming out right.  Playing MS-PacMan, there is absolutely no pink at all even when I play with the POT adjustment.  My Pinky ghost is white!  The walls never get full red.  There is no self test on the 800 so I am not sure what utility yet to use to display a full pallet of colors to see exactly what I am missing though.

 

If I connect Composite out to a monitor / TV, the colors look fine.  So it is just the Chroma and Luminance that is not displaying reds properly and seems to give me a whiteish washed out picture connected to a VGA converter.  All of the black background becomes whitish too instead of a picture on a black background using this adapter.  The same cable combination on an Atari 130XE is fine.

 

Does anyone know where to begin troubleshooting what is causing this?  I bought an Atari 800 for four joystick support, but it bothers me that the colors are messed up. Any help would be great.

 

Osxster

 

 



#2 larryleffaovell OFFLINE  

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Posted Fri May 11, 2018 10:45 AM

Can't help, but if you aren't able to fix it, it may be worth - very worth - to catch up one of the Super Color CPU Card

 sold by tf_hh mentioned in his PDF at https://atariage.com...e-made-by-tfhh/
Got three for my 400 and 800s and the resulted quality is superb!


#3 Osxster OFFLINE  

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Posted Fri May 11, 2018 11:19 AM

Maybe you cut and pasted the wrong thread, but that thread is for memory upgrades for the XL series..

 

Osxster

 



#4 Fox-1 / mnx OFFLINE  

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Posted Fri May 11, 2018 12:20 PM

A few notes:

 

The 800 and the VGA converter need to be the same video system (both PAL, or both NTSC).

There is no self-test in a stock 800.



#5 xrbrevin OFFLINE  

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Posted Fri May 11, 2018 2:56 PM

larry was referring to a pdf price list in his link

 

here is the super color cpu card info link:

http://atariage.com/...color-cpu-card/



#6 Osxster OFFLINE  

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Posted Fri May 11, 2018 4:04 PM

From reading that link, he claims his board is on par with the Atari 800 graphics.  Thus it may not improve video at all over a stock 800.  I guess if its likely my graphics card, I've seen replacement "fully tested" graphics boards with GTIA and all other chips for like $20.  It might be worth buying that unless it could be something else that is bad.  I have not opened it yet to see if there is anything obviously bad, but if generally this type of failure is the graphics card, it might make sense to buy a cheap one which was supposedly fully tested.  Any hints on what could cause these types of problems would be greatly appreciated.

 

Osxster



#7 Stephen OFFLINE  

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Posted Fri May 11, 2018 5:26 PM

From reading that link, he claims his board is on par with the Atari 800 graphics.  Thus it may not improve video at all over a stock 800.  I guess if its likely my graphics card, I've seen replacement "fully tested" graphics boards with GTIA and all other chips for like $20.  It might be worth buying that unless it could be something else that is bad.  I have not opened it yet to see if there is anything obviously bad, but if generally this type of failure is the graphics card, it might make sense to buy a cheap one which was supposedly fully tested.  Any hints on what could cause these types of problems would be greatly appreciated.

 

Osxster

The card with the GTIA/ANTIC is not the cause of bad video on the 800.  It's the inbuilt video circuitry, which this card will bypass.  AA member Bryan was kind enough to allow the use of his "UAV" board in this card.  Without utilizing Sophia of VBXE2, this will give you the absolute best output signal from the Atari which is possible.

 

I have installed the UAV in several machines for myself and customers, and I am also using this card in my 800 with Incognito.  I cannot be happier with the output quality.



#8 Osxster OFFLINE  

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Posted Sat May 12, 2018 5:18 PM

Im not sure he even sells those cards any more since they were a prototype. But in any event, does anyone think my problem is in that board? Will a replacement video card fix it? Could there be circuitry on the main board that could cause this issue?

Osxster

#9 xrbrevin OFFLINE  

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Posted Sat May 12, 2018 6:27 PM

send a pm to tf_hh and find out - he's a nice helpful guy



#10 russg OFFLINE  

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Posted Sun May 13, 2018 9:42 AM

Here's a .ARC of an .ATR with 'TWO56CLR.BAS' that will give you a full colors screen.

Atari used .ARC, it was before .ZIP compression.



#11 russg OFFLINE  

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Posted Sun May 13, 2018 4:22 PM

Here's a .ARC of an .ATR with 'TWO56CLR.BAS' that will give you a full colors screen.

attachicon.gifGRSN1A.ARC

Atari used .ARC, it was before .ZIP compression.

I see this has no attached file.  I don't know how to do it..... I think I did it this time.

Attached Files


Edited by russg, Sun May 13, 2018 4:23 PM.


#12 1050 OFFLINE  

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Posted Sun May 13, 2018 6:11 PM

Could there be circuitry on the main board that could cause this issue?


You could have a bad 4050, A103 that might behave as
your symptoms show. You don't have a replaceable
'board' for video to replace as it were, discrete parts
here and there yes, but no video only system board.

eBay would be just one source for a 4050 chip.

#13 DrVenkman OFFLINE  

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Posted Sun May 13, 2018 6:54 PM

4050 chips are still used today. New production chips are available from any electronic retailer (Mouser, Digi-Key, Jameco, etc). I bought a few to repair an 800XL of mine a few years back. They were about 45 cents apiece at the time, plus shipping.



#14 Osxster OFFLINE  

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Posted Mon May 14, 2018 3:24 PM

This was fun actually, it has been 30 years since I loaded a program from basic on an Atari computer.  Its all coming back..  Maybe 23 years since I used ARC.  Anyway it seems like the colors work with Chroma Luminance, but when the red color get too pink, it turns white instead.  Some of the blue seems to turn white also when its supposed to get darker.  See attached images from my TV...  

 

Both of these images are from the same Atari 800, just I only have this problem with Chroma Luminance.  Composite works color wise, but the quality of composite on this TV is poor, so it looks like crap.  But the colors are there.  This same thing works fine on an Atari 130XE with the same TV / cables.  Hooking this up to an SVideo to VGA converter gives you a very white image overall.  

 

Could this be a bad 4050 chip causing this?  

 

Osxster

 

Attached Thumbnails

  • atari800badcolor_svideo.jpg
  • atari800badcolor_composite.jpg


#15 1050 OFFLINE  

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Posted Tue May 15, 2018 9:36 PM

Yes.




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