Redsam121 Posted November 11, 2023 Share Posted November 11, 2023 I recently acquired an Atari 2600, 4 switch Darth Vader PAL model. I installed a composite video mod but my console will not produce any sound or video signal. Sometime it gives a beeping sound with varying pitch, other rare times it gives static on the screen, but most times no video signal and just static. The seller stated that the thing was tested before transport and was well packaged. Things I've done: Replaced the two capacitors with 830pf 50v ceramic ones. Removed all the required components for composite mod. Checked all the traces, including mods, all good. Checked the voltage regulator, all good. Checked the transistors and inductors, all good. Checked the chips for activity, getting a signal. Checked the AV sockets, getting 1V with the video out. I'm out of things to test and can't come to a diagnosis. Is there anything I've missed? These are pictures my current progress, still no luck. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 12, 2023 Author Share Posted November 12, 2023 After further testing, I still don't have an answer, but I'm confident that the composite mod is not where the fault is. Because the audio is not directly connected to the circuit. The fault is somewhere on the main board itself. I've tested all three chips with the multimeter and all pins are showing activity. I haven't got any other Atari unit to test these chips on though, so I hope they're not where the fault is. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 13, 2023 Author Share Posted November 13, 2023 I've just recapped the board with new capacitors, still no luck. I'm running out of things in my troubleshooting list. Quote Link to comment Share on other sites More sharing options...
juansolo Posted November 13, 2023 Share Posted November 13, 2023 If you get stuck and are in the UK, you could send it to use to have a look at. We've a fair bit of experience with dead Ataris. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 13, 2023 Author Share Posted November 13, 2023 9 minutes ago, juansolo said: If you get stuck and are in the UK, you could send it to use to have a look at. We've a fair bit of experience with dead Ataris. I'm in Australia. Quote Link to comment Share on other sites More sharing options...
juansolo Posted November 13, 2023 Share Posted November 13, 2023 Ah, maybe not then Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 13, 2023 Author Share Posted November 13, 2023 3 minutes ago, juansolo said: Ah, maybe not then I don't want to believe it's the chips that's the problem. Is there any way I can test the chips with just a multimeter. What should I be looking for. Quote Link to comment Share on other sites More sharing options...
juansolo Posted November 13, 2023 Share Posted November 13, 2023 If you've got power everywhere it should be and it's correct you really need a scope to fault find from here. You can then probe the TIA's luma and chroma out's and see what's happening. If you've got signal there but not at the output you trace inbetween and find where you're losing it. If it's not coming out of the TIA, you've got a different issue and a lot more probing... Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 13, 2023 Author Share Posted November 13, 2023 3 hours ago, juansolo said: If you've got power everywhere it should be and it's correct you really need a scope to fault find from here. You can then probe the TIA's luma and chroma out's and see what's happening. If you've got signal there but not at the output you trace inbetween and find where you're losing it. If it's not coming out of the TIA, you've got a different issue and a lot more probing... I don't have a scope to probe and don't won't to fork out that much cash just for this. I performed a multimeter test, pins 5,6,7 (Luma) all showed an average of 190mv each while pin 9 (Colour) showed about 5v. But that doesn't matter if I can't get a signal to monitor. I'll have to search for other options. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 14, 2023 Author Share Posted November 14, 2023 After further probing of components with multimeter, I've determined that both Q200 and Q203 transistors are bad. I will replace them tomorrow and see what happens. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 15, 2023 Author Share Posted November 15, 2023 I've replaced the transistors, still nothing. But I do now get a hanging beep when the console is powered on. Which means it's definitely a chip problem. I don't have the equipment to properly test them so I'll have to figure something out. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 24, 2023 Author Share Posted November 24, 2023 I replaced the TIA chip with a new one, and still nothing. I'm still getting the beeping sounds on start up. It's either the RIOT chip or CPU. Quote Link to comment Share on other sites More sharing options...
fluxit Posted November 24, 2023 Share Posted November 24, 2023 Are you sure that the cart slot is in good shape? Dirty, lose or damaged contacts can cause those symptoms. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 24, 2023 Author Share Posted November 24, 2023 1 hour ago, fluxit said: Are you sure that the cart slot is in good shape? Dirty, lose or damaged contacts can cause those symptoms. I checked the slot with a flash light, I saw no visible damage on the contacts. But, I may try cleaning it later. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 28, 2023 Author Share Posted November 28, 2023 I tried to desolder the reader, but it wouldn't come off so I gave up on that. I then attempted to clean the card reader with cloth, alcohol and cut up card. Still nothing. I'm at the end of my rope. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted November 28, 2023 Author Share Posted November 28, 2023 I tested it on another TV and now I get a white line on the right side. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted December 8, 2023 Author Share Posted December 8, 2023 I have now replaced the CPU, still no change. I get static on one TV and nothing on the other. I only have the RIOT chip and power supply to replace. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted December 11, 2023 Author Share Posted December 11, 2023 I've tested the power supply with a multimeter. The label says between 3-12v at 300mA DC, it's set to 9V (I also tested on 7.5V). My multimeter (Set to mA DC) returns 5.3mA. Is that good or bad? Quote Link to comment Share on other sites More sharing options...
marauder666 Posted December 11, 2023 Share Posted December 11, 2023 300mA isnt enough to run it, stock psu was 500mA. how are you testing the psu output, multimeter needs to have the power pass through it and into console. it not as simple as measuring voltage. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted December 12, 2023 Author Share Posted December 12, 2023 5 hours ago, marauder666 said: 300mA isnt enough to run it, stock psu was 500mA. how are you testing the psu output, multimeter needs to have the power pass through it and into console. it not as simple as measuring voltage. I had the multimeter set to mA DC and had the cables in COM and 10A Input. I plugged the psu in to the console and tested it through there. That's how I got the results. I understand that it's different from voltage. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted December 12, 2023 Author Share Posted December 12, 2023 I have replaced the PSU with a brand new 9V 500mA DC, still no change. All that's left is the RIOT and HEX buffer. Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted December 12, 2023 Share Posted December 12, 2023 Could you take a better picture of the bottom of the AV mod strip board? There's too much glare and I can't see whether the connections are made correctly or not. It looks like the video input wire doesn't connect to anything. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted December 12, 2023 Author Share Posted December 12, 2023 2 hours ago, ChildOfCv said: Could you take a better picture of the bottom of the AV mod strip board? There's too much glare and I can't see whether the connections are made correctly or not. It looks like the video input wire doesn't connect to anything. I've tested it for any bridges or cold joints, nothing found. Here's the under side. Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted December 12, 2023 Share Posted December 12, 2023 The pair of resistors needs to be connected to the same row as the video input and the transistor base. It looks to me like they are both connected to the emitter and output instead. BTW, proper output impedance requires another 68 ohm resistor from emitter to video out. A 470uF capacitor would also be helpful. That "futurewas8bit" article that added the 75 ohm resistor for impedance matching did it wrong. Quote Link to comment Share on other sites More sharing options...
Redsam121 Posted December 13, 2023 Author Share Posted December 13, 2023 6 hours ago, ChildOfCv said: The pair of resistors needs to be connected to the same row as the video input and the transistor base. It looks to me like they are both connected to the emitter and output instead. BTW, proper output impedance requires another 68 ohm resistor from emitter to video out. A 470uF capacitor would also be helpful. That "futurewas8bit" article that added the 75 ohm resistor for impedance matching did it wrong. Can I get a schematic to follow? Quote Link to comment Share on other sites More sharing options...
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