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Denl0

atari 800 xl troubleshooting

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Hi recently I've tried to start an atari 800 xl (pal) . I keep getting a blank screen on it.

 

I've read other threads concerning this problem.

 

Things I've tried so far:

 

-Measure output. I got 3 times 5 volt inside the computer.

-Refit all microships.

-Using star raiders cartridge also didn't work.

-None of the parts get's really hot.

 

 

Things I've noticed:

 

Sometimes I get yelow screen flash but then it turns black.

Sometimes with star raiders I have very thin blue lines. And sometimes a nice beeeeep sound.

 

When I press reset the blue thin lines or the sound goes away.

 

If I use UHF it finds the atari at 62 Mhz here there are blue dots around 1 cm appart from each other moving.

 

I do remember that it was broken when we put it away 10 years ago. It was broken suddenly 1 day it was working , the day after it diden't boot.

 

Are there any other things I might have to try?

 

I can't really swap ic's since we only have one atari 800xl

 

Are there any other common bugs on the pc. I think it's not damage from being old.

 

My dad suspects that cartridge bay is somehow stopping the system from booting?

 

Thank you for you're help!

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I havn't looked at the back of the pcb are there any chips there?

There are no chips or anything on the bottom of an 800xl mb except solder spots and board traces.

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There are no chips or anything on the bottom of an 800xl mb except solder spots and board traces.

Unless there has been one of the modern upgrades done to it like VBXE that sometimes requires the need to mount something in the way of the upgrade board go on backside.

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just the usual replace ram,os,cpu,pokey,mmu. easier if you have a spare working xl with all chips socketed to swap parts with

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Wouldn't it still show a screen if the ram was broken? + It was broken suddenly not because its old.

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Wouldn't it still show a screen if the ram was broken? + It was broken suddenly not because its old.

Long time, no response.

 

From the 800XL Field Service Manual:

 

Black or Grey screen (not just a dead screen, it comes up with a black or grey screen).

 

Clock circuit:

Y1 (a crystal), transistors Q8, Q9, capacitor C109

 

Other circuits:

U2, U7 to U20, U22, U23, U26 to U30

 

U2 a 74LS138 decoder 14 pin LS chip 2nd chip down from cart port

U7-Antic bottom second from left

U17- GTIA left most bottom

U8 - CPU 3rd from left bottom large chip

Drams on the left

U18 IC 74LS08

U19 74LS14 Hex inverter

U 20 Hex buffer CMOS

U 22 Pokey second up on fourth row from left

U23 PIA rightmost bottom Large chip

OS ROM U5 there are two smaller chips up the middle, it is the bottom, slightly bigger one

the BASIC ROM U4 is the smaller chip just up from OS ROM

 

All this does you no good, since you don't have a working board to try swapping with.

If you really knew what you're doing, an oscilloscope.

Edited by russg

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