strattsp Posted February 18, 2007 Share Posted February 18, 2007 I just got done with the A/V mod described in the FAQ, and the picture looks great, except it is in b&w. I have been over the circuit several times, and I am convinced that I have constructed it correctly. The only thing that seems to be not right is that I am not getting a full 5V from the Atari. The power regulator is putting out 4.7 V Could this be the problem? I know enough to be dangerous, but not enough to know what's wrong. Is there a certain resistor I should adjust? Is 4.7V okay, or should I replace the power regulator? -Steve Quote Link to comment Share on other sites More sharing options...
strattsp Posted March 16, 2007 Author Share Posted March 16, 2007 Well, I got it working. I knew it was a problem with the chroma, since I was getting a perfect B&W picture. So on the off chance that the schematic was wrong, I tried pulling the chroma signal from the next resistor (the one on the end), and there was my chroma. Since this is my first 5200 mod, I don't know if it is a problem with the schematics, or if there was a design change on the 5200, but I know that I'm getting chroma from the resistor on the end, not the one shown in the FAQ. Now my only problem is that the picture seems a little dark. Anyone know how to tweak the brightness? -Steve Quote Link to comment Share on other sites More sharing options...
Gunstar Posted April 20, 2007 Share Posted April 20, 2007 (edited) Well, I got it working. I knew it was a problem with the chroma, since I was getting a perfect B&W picture. So on the off chance that the schematic was wrong, I tried pulling the chroma signal from the next resistor (the one on the end), and there was my chroma. Since this is my first 5200 mod, I don't know if it is a problem with the schematics, or if there was a design change on the 5200, but I know that I'm getting chroma from the resistor on the end, not the one shown in the FAQ. Now my only problem is that the picture seems a little dark. Anyone know how to tweak the brightness? -Steve I too, recently did this upgrade, and ran across the exact same problem with the schematic being wrong as to where the chroma signal is and did exactly what you did and got my color. But, my upgrade too, is dark, what SHOULD be white, like text, is grey. I am pretty certain that this is ALSO a problem with where the mod instructions say to get the luma signals from, it seems to be missing one of the four (lum 0, 1, 2, 3) signals, or that is, one of the points the mod says to get the lumina signals from is WRONG. most likely the one for the brightest level(i.e., white). I am currently attempting to find another source of schematics showing where the 4 Lumina signals are supposed to be tapped. If anyone can help, please do. Here is a link to the ONLY homebrew video hack instructions I can find. The first "schematic" shows where to get the Chroma/lumina and sync signals. It has already been established that the Chroma is actually the LAST resister and not the second to last (in the row) as pictured here. I've done the mod, connected it to the CORRECT chroma signal point, but the Lumina is still off. I've double checked the circuit several times, and I know it's right, and it's the same ciruit used for 2600 and 7800 mods, so I know the circuit is good, so it MUST be a wrong point in the schematic for one of the Lumina signals (0, 1, 2, 3). Who has done this upgrade and can tell me the correct locations of the lumina signals? Either that, or these are all the correct locations for the lumina signal, but one or more are labeled incorrectly (for example maybe 0 and 1 should be swapped), so that they are incorrectly hooked to the circuit and the different resistances throw the lumina off so the picture is darker than it should be. Now, I know I can do a process of elimination, but it would be nice to know and just make one adjustment. http://www.atarihq.com/5200/5200faq/04_13.html Edited April 20, 2007 by Gunstar Quote Link to comment Share on other sites More sharing options...
82atari5200 Posted April 20, 2007 Share Posted April 20, 2007 (edited) I made 3 of these that worked for a little bit. Burned up 3 motherboards in the process. I used one of those white prototyping boards that you can get from Radio Shack. Then but them on an actual pcb. It's best just to go to 8bitdomain.com and order one from him for 30 something dollars. Well worth the price. I also found a couple schematics for the 800xl video board that you can use as well. Just tap into the GTIA instead of pulling it off of the resistors. Edited April 20, 2007 by 82atari5200 Quote Link to comment Share on other sites More sharing options...
Gunstar Posted April 20, 2007 Share Posted April 20, 2007 I made 3 of these that worked for a little bit. Burned up 3 motherboards in the process. I used one of those white prototyping boards that you can get from Radio Shack. Then but them on an actual pcb. It's best just to go to 8bitdomain.com and order one from him for 30 something dollars. Well worth the price. I also found a couple schematics for the 800xl video board that you can use as well. Just tap into the GTIA instead of pulling it off of the resistors. Good point, it probably would be easier to tap the signals off of the GTIA, should be easier to find a GTIA pinout. As for 8bitdomain, I'm strictly a do-it-yourself-er, I'm not going to pay $30 for any board, when I just spent about $3 for parts and about 4-5 hours of my time and built my own circuit, which I KNOW is fine, it's just a reliable source of the Lumina signals I'm looking for. What about the schematics for the 800XL video board? I can't use them unless you post a link. Quote Link to comment Share on other sites More sharing options...
Gunstar Posted April 20, 2007 Share Posted April 20, 2007 I made 3 of these that worked for a little bit. Burned up 3 motherboards in the process. How can you POSSIBLY have burned out three motherboards making this simple circuit?!? It sounds to me like you need to stay, far, far away from electronics if you cause that type of damage. I've got an electronics degree, and I can't possibly imagine under what circumstances I would accidentally burn out an entire MOBO making this simple circuit, which doesn't even need to go anywhere near the MOBO until one is ready to connect it to the +5v, ground and seven wires for sync, lumina, chroma and audio. Maybe I shouldn't be taking advice from you afterall... Quote Link to comment Share on other sites More sharing options...
82atari5200 Posted April 21, 2007 Share Posted April 21, 2007 Sorry I don't have a degree in electronics. Sorry for offering my worthless two frigging cents worth. You smug enlightened individuals can kiss my ass. I didn't burn out the entire motherboard I burned out the video buffer. Sorry for not being specific. Quote Link to comment Share on other sites More sharing options...
Gunstar Posted April 21, 2007 Share Posted April 21, 2007 (edited) Sorry I don't have a degree in electronics. Sorry for offering my worthless two frigging cents worth. You smug enlightened individuals can kiss my ass. I didn't burn out the entire motherboard I burned out the video buffer. Sorry for not being specific. Take it easy, my comments were light-hearted. And as a matter of fact, your advice about the GTIA was taken and used. Edited April 21, 2007 by Gunstar Quote Link to comment Share on other sites More sharing options...
Gunstar Posted April 21, 2007 Share Posted April 21, 2007 (edited) Well, I've connected the 4 luminance wires to the signal sources on the GTIA, and the results are exactly the same, so I guess the original schematics are right except for the color point. The picture is just too dark, everything that is supposed to be white is grey. The basic circuit in this mod is the exact same circuit used for the 2600 and 7800 video mods, which I've done before and they work great, so I've come to the conclusion that this circuit can not just be carbon-copied from the 2600/7800 mods to use with the 5200. Apparently the TIA and GTIA chips are not identical where the luminance signals are concerned. I'm pretty sure the problem is just the resistances used for the four lumina signals; while they work fine for the 2600/7800, they will have to be tweaked for use with the 5200. So, since apparently no one else has noticed this problem and corrected it, I will redo the circuit, tweaking it for the 5200 and post the results for proper resistances when done. Unless someone else who has already been through this (there MUST be someone) can provide the proper resistance levels for the circuit and save me the trouble. Edited April 21, 2007 by Gunstar Quote Link to comment Share on other sites More sharing options...
Gunstar Posted April 21, 2007 Share Posted April 21, 2007 (edited) Well, after further testing, the circuit does seem to be working properly, it was apparently my TV/VCR combo I was testing it on that was making it look too dark, even with contrast&brightness turned all the way up. I'm not sure WHY, as every other system I have, including others with this same circuit, seem fine. What happened was I hooked up my Commodore 1084s monitor by my work station so I could tweak the circuit with the monitor showing the picture (so I didn't have to tweak something, then drag it into my living room to test on the big TV), and everything looks perfect when showing on the monitor, the whites are white and not grey. Long story short, the problem, for whatever strange reason, was with my 32" T.V. or the VCR I had the system plugged into and then to the T.V. I'll have to plug it in directly to the T.V. to find out if the T.V. or the VCR is the culprit. Edited April 21, 2007 by Gunstar Quote Link to comment Share on other sites More sharing options...
SINGLE TOOTH Posted June 7, 2007 Share Posted June 7, 2007 Did you ever find out the problem? Quote Link to comment Share on other sites More sharing options...
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