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Buchau

Report on “untested” 800XL and 600XL

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800XL came with Ingot supply, tested to 5V ok, but used Raspberry Pi Zero 2.5 amp instead(has 5.33 and 5.19V under load output) Connect to LCD monitor/Tv and SIO2SD. Unit boots to lothareks menu, but has loud noise that should not be there and video not clean. Open up and find OS rom not fully seated. Board is fully socketed.Remove C56(was installed, not shown on schematic from Sams)bridge L5. Video much better and noise gone.Test mode shows 48 blocks Ram(FRE(0)=37873.connect keyboard.Have stuck key.Type 4 with Mylar.Take apart and reduce spring tension on bad key. Unit seems to work OK except the blue screen turns to green shade when idle for a while. Does not seem to affect game play. Unit missing 800XL badge on top cover.

600XL also came with Ingot supply(tested to 5V),not used. Could not get output to show on LCD monitor/Tv set to ch 2or3. Decided to install UAV and Din5 to get composite video. Now have video and sound. Maybe Tv did not pickup Rf from Atari? Install 64K upgrade with 4464-10 chips and 3 wire. Test mode shows 40 blocks, not 48, but FRE(0)=37902. Unit works fine with games.

What is causing blue to green change on the 800XL?

Thanks for looking.

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Try adjusting the color.  There should be a little slotted potentiometer for this purpose on the board.  It's very easy to get green instead of blue if it's just a bit off of optimal.

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16 hours ago, Sugarland said:

Yes press a key to stop the screen changing color.

I think you are referring to the “screensaver” function. It’s not that.What I see is a gradual change from strong blue to weak blue then greenish tint and so on. This happens over 15 or 20 minutes and keeps going until it is grey. Kind of like a component is changing value as it heats up? Game play does not seem to be affected?

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watch your power supply and the voltage going out of the color trim pot... you may have a weakening transistor in the power supply or the the video drive.

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On 3/19/2021 at 9:44 AM, Buchau said:

used Raspberry Pi Zero 2.5 amp instead(has 5.33 and 5.19V under load output)

Sometimes these "modern" small switching power supplies have poor filtering, and have a lot of noise on their DC output. The computer itself has little for filtering, so this noise will easily pass through to the audio and video output. Try another power supply as well. Although you also noted you were able to clean it up a lot removing C56/Bridge L5.

 

On 3/19/2021 at 9:44 AM, Buchau said:

Maybe Tv did not pickup Rf from Atari?

Using a generic RCA wire will often result in poor RF signal transfer. Try with an actual Atari RF cable - the one with the box in the middle with ferrite coil, etc.

 

On 3/19/2021 at 9:44 AM, Buchau said:

Test mode shows 40 blocks, not 48

This happens when you enter self test from BASIC by typing BYE or with BASIC enabled. Boot holding OPTION key to see 48 blocks.

 

On 3/19/2021 at 9:44 AM, Buchau said:

What is causing blue to green change on the 800XL?

Try adjusting the colour pot. Note current position, then rotate it back and forth a bunch of times to 'clean' the contacts inside, eventually settling back to original position, or correct colour to the eye.

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