R4ngerM4n Posted July 20, 2012 Share Posted July 20, 2012 I hooked up my old Atari 400 on TV today and I was shocked: Everything is displayed correctly, but there are no colors (BASIC screen is grey but should be blue). Other computers work properly with that TV. I used another rf-cable but same problem. Putting in a game cart I noted that sound is missing, too. The internal speaker (for keyboard click) doesn't work either. I opened the case and checked all sockets and connectors - everything seems to be in place. Any idea what the cause of this failure might be? Quote Link to comment Share on other sites More sharing options...
+Stephen Posted July 20, 2012 Share Posted July 20, 2012 Hmm - lack of colour and no keyclick point to a problem with the GTIA. Regular sound of course is generated by Pokey. Everything in a 400 is socketed. Try removing & re-inserting it. If that doesn't work, try one from another machine. The other thing you may want to check, is the small potentiometer. If they lose contact due to corrosion, I believe they can also cause a lack of colour. Gently turn it back and forth a little bit. Is it possible that your TV is not tuned properly? I know the 400 is RF only. 1 Quote Link to comment Share on other sites More sharing options...
Marius Posted July 20, 2012 Share Posted July 20, 2012 Stephen gave several options to check... And one more thing: the RF modulator could be defect. 1 Quote Link to comment Share on other sites More sharing options...
+orpheuswaking Posted July 20, 2012 Share Posted July 20, 2012 Also the trim pot for color (although that doesn't explain lack of sound) Quote Link to comment Share on other sites More sharing options...
Marius Posted July 20, 2012 Share Posted July 20, 2012 (edited) Also the trim pot for color (although that doesn't explain lack of sound) Stephen already suggested that in his second last sentence... but indeed... that is an option too. Edited July 20, 2012 by Marius1976 Quote Link to comment Share on other sites More sharing options...
+orpheuswaking Posted July 20, 2012 Share Posted July 20, 2012 Pft, I don't read anything that Stephen guy writes! 2 Quote Link to comment Share on other sites More sharing options...
olavese@online.no Posted July 21, 2012 Share Posted July 21, 2012 When I tried an 800 once, it was a US model and I had a PAL TV. Black and white picture ... You haven't moved? Quote Link to comment Share on other sites More sharing options...
R4ngerM4n Posted July 21, 2012 Author Share Posted July 21, 2012 I tried the potentiometer - nothing changed, TV-output remains black and white. The computer is PAL and the TV, too. I tried the TV with another 400 and everything works fine, so I think it's a hardware problem of the 400 under question. I have the feeling that the modulator is broken because I noted after some further tests that the screen flashes sometimes (scrambled but with colors in). How to get a new PAL-modulator (or board)? Any vendors around? Quote Link to comment Share on other sites More sharing options...
Rybags Posted July 21, 2012 Share Posted July 21, 2012 Try the other channel on the switch. Another thing - the RF cord plugs into the same type of plug inside the machine as you see on XL/XE. Those plugs are made of rubbish material that easily oxidizes and can degrade the video signal. Quote Link to comment Share on other sites More sharing options...
R4ngerM4n Posted July 21, 2012 Author Share Posted July 21, 2012 Try the other channel on the switch. Another thing - the RF cord plugs into the same type of plug inside the machine as you see on XL/XE. Those plugs are made of rubbish material that easily oxidizes and can degrade the video signal. No difference Quote Link to comment Share on other sites More sharing options...
russg Posted July 21, 2012 Share Posted July 21, 2012 (edited) Try the other channel on the switch. Another thing - the RF cord plugs into the same type of plug inside the machine as you see on XL/XE. Those plugs are made of rubbish material that easily oxidizes and can degrade the video signal. No difference You have a working 400. So, you can swap chips and see if that works. Specifically, someone mentioned the GTIA. GTIA is a CO14805-22. POKEY CO12294B-01, CPU CO14806-03, Antic CO12296, PIA CO14795-12. I think that's all the 40 pin LSIs. Also, you mention a BASIC screen. You have to have a BASIC cart in to get the BASIC READY blue/white screen. I think you get a memo pad with no other boot. Also, wiggle the RF cable at the jack, see if there's a bad connection. And wiggle the channel select switch. I've had a bad one of those. These are NTSC chip numbers, some different for PAL, your 'Location' is sofa cushion. I don't think 400 were made in PAL. Edited July 21, 2012 by russg Quote Link to comment Share on other sites More sharing options...
Mclaneinc Posted July 21, 2012 Share Posted July 21, 2012 I'm betting the modulator is up the duff...They were put in very poorly in the early models, it might be worth checking where the modulator is and running a iron over the solder points (machine off of course) Quote Link to comment Share on other sites More sharing options...
mimo Posted July 22, 2012 Share Posted July 22, 2012 Pal 2600's use the same modulator as the 400, Finally a use for a vcs Quote Link to comment Share on other sites More sharing options...
R4ngerM4n Posted July 23, 2012 Author Share Posted July 23, 2012 (edited) I did some tests and it's definitively the color circuitry on the CPU board. After changing IC 74LS74 and IC 74LS244 from the working board to the non-working, one of those ICs was burnt. So now I have two CPU boards with the same problem. I ordered both ICs so I can see which one actually went broke (I dont own analyzer hardware). How to troubleshoot the resistors and capacitors on the board? Any experiences or advices? Edited July 23, 2012 by R4ngerM4n Quote Link to comment Share on other sites More sharing options...
russg Posted July 23, 2012 Share Posted July 23, 2012 (edited) I did some tests and it's definitively the color circuitry on the CPU board. After changing IC 74LS74 and IC 74LS244 from the working board to the non-working, one of those ICs was burnt. So now I have two CPU boards with the same problem. I ordered both ICs so I can see which one actually went broke (I dont own analyzer hardware). How to troubleshoot the resistors and capacitors on the board? Any experiences or advices? edit: This isn't bright. The 400 uses a 9V AC, not a 5V brick. Sorry Are you using the same power supply on both 400s? The 'ingot' power supply is known to damage. Edited July 23, 2012 by russg Quote Link to comment Share on other sites More sharing options...
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