rasty Posted May 20, 2003 Share Posted May 20, 2003 Hi All! I definitely need your help & suggestions about some issues I'm having with my (pal) 7800 when in 2600 mode. After the system's been on for a short while (usually just a few minutes), colors will start to drop to b&w and then back to color every about half a second. This goes on forever I've tried a few simple solutions like direct TV connection (no switchbox), but since I'm not a hardware 7800 expert at all, I have not messed with the circuitry. But I'm willing to do so if you have suggestions! 7800 mode is fine, no color loss. Ah, some time ago I've done the little mod described here (Cuttle Cart mod), but I recall the issue was already there.. Thanks in advance for your opinions! Regards, Rasty.- Link to comment Share on other sites More sharing options...
cschell Posted May 21, 2003 Share Posted May 21, 2003 Eckhard has a similar problem with a PAL 7800. I think it is related to an unstable power supply. The Atari consoles use basically unregulated power as an input to the color pot, so if you're getting variation on this input, it will cause the same effect as turning the color pot. Eckhard tells me that the PAL consoles require very little adjustment to the color pot to make the colors go to black and white. Replacing the power supply might help this problem. Chad Link to comment Share on other sites More sharing options...
rasty Posted May 21, 2003 Author Share Posted May 21, 2003 Eckhard has a similar problem with a PAL 7800. I think it is related to an unstable power supply. The Atari consoles use basically unregulated power as an input to the color pot, so if you're getting variation on this input, it will cause the same effect as turning the color pot. Eckhard tells me that the PAL consoles require very little adjustment to the color pot to make the colors go to black and white. Replacing the power supply might help this problem. Ahh that's good news, thanks..! In fact even the background noise kind of pulsates, I'll definitely work in the power supply direction. Luckily it's a standard 9v 1a, I'll just have to cut the cord and replace with another one. Thanks again! Fabrizio.- Link to comment Share on other sites More sharing options...
rasty Posted May 22, 2003 Author Share Posted May 22, 2003 Hi Again! I've just replaced the power supply, however the color drop issue is still there I wonder whether playing a bit with the pots could be of some use? Thanks again! Fabrizio.- Link to comment Share on other sites More sharing options...
+Mitch Posted May 22, 2003 Share Posted May 22, 2003 Might work. Just make sure you change the 2600 pot and not the 7800 one. Mitch Link to comment Share on other sites More sharing options...
rasty Posted May 22, 2003 Author Share Posted May 22, 2003 Might work. Just make sure you change the 2600 pot and not the 7800 one. Ehm.. which's which? Rasty.- Link to comment Share on other sites More sharing options...
+Mitch Posted May 22, 2003 Share Posted May 22, 2003 I don't have a PAL system open at the moment but the schematic says R43 is the 2600 one and R42 is the 7800 one. If those numbers match what's on your board then that's probably right. Mitch Link to comment Share on other sites More sharing options...
cschell Posted May 23, 2003 Share Posted May 23, 2003 Bummer, Didn't mean to lead you astray. The voltage for the color pots is held by a chain of two diodes. If you have an oscilloscope or a voltmeter you can monitor the voltage at the high side of the pots and see if it is stable. The pots will have terminals, you'll want to monitor the one with the highest voltage. It should constant. If it is, the pot and it's voltage levels are probably not your problem. Chad Link to comment Share on other sites More sharing options...
Eckhard Stolberg Posted May 23, 2003 Share Posted May 23, 2003 I had the same problem with my 7800s and a 2600 Jr too. As it turns out the voltage is changing a bit when the console heats up. As Chad has pointed out, this is the equivalent to turning the colour adjustment pot a bit. If you try adjusting the colour pot for the 2600 mode yourself (it's the one further away from the cartridge connector), you can see that there are several positions where the colours turn gray. Also there are borderline positions where the colour gets unstable. To fix your problem you should wait until your console has warmed up and then adjust the colour pot (R43, as Mitch mentioned) to give you good PAL colours. Try out what the maximum and minimum position are for getting good colours and set the pot to be in the middle between the two. That way you'll still get good colours from a cold 7800 when the voltage is still a little different. Ciao, Eckhard Stolberg Link to comment Share on other sites More sharing options...
rasty Posted May 24, 2003 Author Share Posted May 24, 2003 Hi guys! I must thank you all once again for all the help which led me to (seemingly) fixing the problem! I've played a bit with the pot (VERY sensible!) measuring the volts when cold and when hot, and I think I've got a decent regulation. I've kept the 7800 on for quite a while, then made it cool down again for a few times and the colors were fine all the way throu.. woo!! Great! Thanks again! Now my system's ready for CuttleCart 2 Regards, Fabrizio.- Link to comment Share on other sites More sharing options...
cschell Posted May 25, 2003 Share Posted May 25, 2003 Glad to hear that you got it working. Chad Link to comment Share on other sites More sharing options...
Like us on Facebook
Follow us on Twitter
AtariAge on Instagram
Watch us on YouTube
Chat on Discord
Recommended Posts
Archived
This topic is now archived and is closed to further replies.