mamejay

Have a look at this thread http://www.atariage.com/forums/topic/173828-7800-pal-b-composite-vout-scheme/ Towards the bottom I created a perf board diagram which worked fine on my PAL 7800

I have scored some bargains as sellers are just too lazy to give console a wipe down. I love getting old consoles and gutting them, totally washing the cases and then putting them back together and getting 200% more than I paid for them.

Correct. Also the 2 x 10K resistors on the chroma lines should be trimpots just so you can get the colour just right.

Try this one. It exactly what the schematic above is.

That is the same circuit I posted above. I have tried both that mod and the S-Video mod. S-video provides much better results than the composite circuit. I have also converted the S-video to composite and get better video than that circuit you mentioned.

More games now tested on a PAL system Hat Trick = Colours all wrong but playable Choplifter = Will not start On-on-One = Colours wrong but playable Karateka = Plays but not sure. Joystick repsonse seems really slow. Maybe this is how the 7800 is. Xevious = Playable. Graphics glitch at bottom of the screen

Found out what the problem was. Was using PN100 transistors instead of 2N3904 as I was told they are compatible. When replaced with the 2N3904's it works perfectly.

BTW, The 26000 Chroma pin mentioned in the picture is incorrect. I had to find another point to grab the Chroma signal. You can get it from the next row of resistors next to the Audio outputs. about the 3rd one down.

Got it working tonight. Look very sharp!! I used variable resistor pots and adjusted till it looked right. I will post up the values soon.

OK, I finally got this damn mod working. Sort of. The picture is nice and clear now. I have just one problem. My TV constantly displays the S-video symbol. It flashes on screen. If I go into the TV settings they flash up then disappear. I suspect there may be voltage running into the s-video. Anyone else got something like this happening? For anyone that wants it here is a perfboard diagram that I put together.

Finally found out what the problem was. I must have fried the TIA chip. I got myself a desoldering gun and removed the TIA chip and added a socket and replaced with another TIA. System works perfectly now.

The second one works perfectly but there was some static that has affected one of the chips on the 7800. This was my fault for not discharging the motherboard.

Thanks for that. From what I have read the TIA controls the Atari 2600 side of things and just the buttons for the controllers. This would make sense that the fire button is stuck on and that the 2600 won't run games if I killed the TIA. Everything on this board is soldered to the MB but I have a desoldering gun coming and will add sockets to the MB. I have some spare TIA chips that i got to repair some 2600 JNR's. From what i can tell these are the same for the 2600 and 7800.

I could not get this mod working on the PAL 7800. i suspect that the resistance values need to be tweaked to get the correct picture. I found this video on youtube. Its only for a composite mod but the quality looked pretty good. I have drawn up a board if you wanna make the circuit. Really easy and small. Just be careful when working on the 7800 that you unplug the console and hit the power button to discharge it. I did not do this and my soldering iron shorted something out and now i have problems with my console.

I have a PAL 7800 and have only tried the built in Asteroids game. I have a few PAL 7800 games but they are all sealed and I didn't want to open them. I will try one out and see if that works. The problem happened when I tried to grab the audio signals from R33 and R32. I checked on the schematics for R33 and saw that it it feeds back to the TIA chip. That is why I am suspecting that its that chip.

Very clever of you. I didn't realise. Now if someone could tell me what chip on the board that could be the problem that would be great. I suspect the TIA may have a problem as I believe it controls the controllers and the 2600 video. I have some spare 2600Jnr's here that I can steal chips from. Will the TIA from a JNR work on the 7800? From what I can tell they are the same chip.

Hi Guys, Got myself a PAL 7800 and decided to do a basic AV mod on it. Got the video working fine so I decided to do the audio. I disconnected the the 2 x resisters for the audio and was going to grab the audio from there. When i fired the system up the built in Asteroids games automatically went into a game. The fire button does not work but everything else does. Seems like the fire button is stuck on. If I try a 2600 cart now I get a flickering bar on screen. It was working for a short while before it died. I reverse the mod but I get the same symptoms now. Any idea of what could be the problem?

Hello Everyone, I too have just got myself a PAL 7800 which I want to AV mod. I have build a strip board diagram to build the circuit from. I have attached it to make it easier if you want to build one yourself. It is exactly the same as your attached schematic except for I have set resisters for R5 and R6 instead of the 10K pots. You can add the pots instead if you like. Can someone with a bit more experience in circuit board making have a check over this and let me know if they think I have designed it correctly?

Just pulled apart the SCART lead for my 7800 and it looks like its only RGB. Looks like I need to get a RGB to component converter now! Damn

I will do some thorough testings once I get mine delivered. I am a little concerned with seller I brought the 7800 off. He has not responded for 3 days to any of my emails. Could be a language barrier but still at least let me know that its under way.

Hey 5-11under, I have performed a microswitch joystick mod on one of my bad controllers. I found the tut on youtube. It works great but I cannot use the existing spring so the joystick feels loose. Have you performed a microswitch mod before? If so what did you use for a spring to keep the joystick firm?

It does RGB + composite + mono sound.If TV accepts RGB, RGB is shown. If TV doesn't accept RGB, composite is shown. (Most of the times, a TV with 2 or 3 scart inputs only takes RGB from one of them, the others are composite only; plug in the good one). Thanks for that Rastignac, I do not have a SCART TV as I live in Australia but was going to have a play around with soldering some outputs to the pins to test. If composite works this will work out fine for me. Now all I need is some PAL 7800 games. They seems to be heaps more expensive than their NTSC counterparts. Anyone interested in getting rid of some PAL doubles they may have?

Sorry to bring up an old thread. I see from the pictures that the SCART lead has pin 20 and pin 15 present. I check online and worked out that they are Composite Video In / Luminance (Pin 20) and RGB Red In / Chrominance (Pin 15) Would this mean I can pull an S-Video signal from the SCART cable? Just picked myself up a French 7800 and really need S-Video or composite out.

Thanks for the links. One thing though. I am looking at some of the pictures from the photographs thread and it has a picture of the SCART connector. I have compared the available pins and it looks like there is RGB as well as S-Video (Chrominance, Luminance) pins. Has anyone tried to tap the S-Video out and see what the result was?

Hi Guys, Scored myself a French 7800 console with SCART connector. Waiting on it to be delivered now. Just wondering what it actually outputs? Cannot find any firm information whether it outputs RGB only or if it does S-Video and composite also. Any help will be appreciated.