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easier 7800 Composite video mod


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#26 Rybags ONLINE  

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Posted Mon Jun 30, 2008 8:36 AM

Thanks. The modulator seems fine, it's just the cheapo RF plug on the console is rusted and worn.

I actually had best results by using a succession of adaptors and RCA cable, from memory last time I used the machine.

#27 ApolloBoy OFFLINE  

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Posted Mon Jun 30, 2008 4:01 PM

So it's alright to cut all 4 pins off the RF modulator if you don't need RF? This sounds like a mod I wanna try.

#28 puppetmark OFFLINE  

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Posted Mon Jun 30, 2008 7:33 PM

So it's alright to cut all 4 pins off the RF modulator if you don't need RF? This sounds like a mod I wanna try.


Yep. If you don't ever want to use the RF output, you can cut the 4 pins.

#29 Underball OFFLINE  

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Posted Wed Jul 2, 2008 3:48 PM

Just did this mod.

AWESOME!!!!

Two things:

1. - I couldn't find a 75ohm 1.4 watt resistor at radio shack, so I used a a 47ohm + 3 10ohms in series. 1000x better than RF though.

2. - the audio portion is a problem in puppet mark's version. there's no pokey sound coming through.

So I did a combination of Puppetmark's video circuit and Almost Rice's audio circuit.

Perfect. And I think it cost a total of like $10 at radio shack.

Edited by Underball, Wed Jul 2, 2008 7:01 PM.


#30 Almost Rice OFFLINE  

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Posted Wed Jul 2, 2008 8:20 PM

Perfect. And I think it cost a total of like $10 at radio shack.


That's what attracted me to doing this. I was afraid of waiting on anyone else to sell me one so I looked up the video signal myself one day. I knew I chose that audio location for a reason. :D

Edited by Almost Rice, Wed Jul 2, 2008 8:25 PM.


#31 Underball OFFLINE  

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Posted Wed Jul 2, 2008 8:51 PM

While I had her open, I changed the LED to Yellow.

#32 Prodos8 OFFLINE  

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Posted Wed Jul 2, 2008 9:04 PM

Any reason this won't work on the 2600 as well?

I tried to tap the video from the RF modulator and run it through the transistor amp circuit detailed in this thread and all I got was a black screen. There're five pins on the 2600's RF modulator and I determined pin 1 was gnd and pin 5 was +5v I tried to pull video off of pin 3 & 4. No luck though.

#33 Almost Rice OFFLINE  

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Posted Wed Jul 2, 2008 9:37 PM

Any reason this won't work on the 2600 as well?

I tried to tap the video from the RF modulator and run it through the transistor amp circuit detailed in this thread and all I got was a black screen. There're five pins on the 2600's RF modulator and I determined pin 1 was gnd and pin 5 was +5v I tried to pull video off of pin 3 & 4. No luck though.


You might want to try this

It depends on which 2600 you are modding.

This is a thorough analysis of different circuits

Edited by Almost Rice, Wed Jul 2, 2008 10:08 PM.


#34 puppetmark OFFLINE  

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Posted Wed Jul 2, 2008 10:10 PM

2. - the audio portion is a problem in puppet mark's version. there's no pokey sound coming through.

So I did a combination of Puppetmark's video circuit and Almost Rice's audio circuit.


Interesting. I checked again and I am getting 2600 and 7800 sound. I wonder what I am missing here. How did you hook up the audio?

Edited by puppetmark, Wed Jul 2, 2008 10:15 PM.


#35 Underball OFFLINE  

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Posted Thu Jul 3, 2008 1:57 AM

2. - the audio portion is a problem in puppet mark's version. there's no pokey sound coming through.

So I did a combination of Puppetmark's video circuit and Almost Rice's audio circuit.


Interesting. I checked again and I am getting 2600 and 7800 sound. I wonder what I am missing here. How did you hook up the audio?

It's not 7800 sound that's the problem. It's POKEY sound. The 7800 sound effects are fine. But the few games that use the pokey for music - Commando, Ballblazer, Froggie, Beef Drop, have no music with yours.

Also - there's a bit of ghosting when the brightness is turned up enough. Think that 91k replacing R15 will fix that?

#36 puppetmark OFFLINE  

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Posted Thu Jul 3, 2008 7:04 AM

It's not 7800 sound that's the problem. It's POKEY sound. The 7800 sound effects are fine. But the few games that use the pokey for music - Commando, Ballblazer, Froggie, Beef Drop, have no music with yours.

Also - there's a bit of ghosting when the brightness is turned up enough. Think that 91k replacing R15 will fix that?


Oops! Now I understand. I don't have any of those carts to test. Where did you pick up the POKEY sound?

replacing R15 with a 91K will actually bring the brightness down a notch. I don't think it will help with ghosting. Many Atari systems have a slight ghosting problem due to the way the color signal is joined with the luminance signal. I guess Atari figured since the systems will work through RF anyway, the ghosting won't be noticed as the RF degrades the picture anyway.

When I hooked my 7800 up to a composite monitor and my TV and I don't think I noticed any ghosting but I will look again and see. I wasn't looking for any either, I was just amazed at how much better it looked. BTW, nice work on your 7800. Its good to have multiple people try something like this. Maybe we should call it the 7800 $10.00 super video Mod?

#37 Almost Rice OFFLINE  

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Posted Thu Jul 3, 2008 9:26 AM

It's not 7800 sound that's the problem. It's POKEY sound. The 7800 sound effects are fine. But the few games that use the pokey for music - Commando, Ballblazer, Froggie, Beef Drop, have no music with yours.

Also - there's a bit of ghosting when the brightness is turned up enough. Think that 91k replacing R15 will fix that?

Oops! Now I understand. I don't have any of those carts to test. Where did you pick up the POKEY sound?

replacing R15 with a 91K will actually bring the brightness down a notch. I don't think it will help with ghosting. Many Atari systems have a slight ghosting problem due to the way the color signal is joined with the luminance signal. I guess Atari figured since the systems will work through RF anyway, the ghosting won't be noticed as the RF degrades the picture anyway.

When I hooked my 7800 up to a composite monitor and my TV and I don't think I noticed any ghosting but I will look again and see. I wasn't looking for any either, I was just amazed at how much better it looked. BTW, nice work on your 7800. Its good to have multiple people try something like this. Maybe we should call it the 7800 $10.00 super video Mod?


The ghosting is more like an bright aura around images. If you play any game where you have a black background and lots of bright characters, you will see it. Robotron is one I see the ghosting(bright aura around the each image). Turning down the brightness on the monitor is what I do, but an internal solution would be best.

The sound was important to me because I needed it to play Beef Drop, I had to join R5 and R6 puts all the signals together if I remember the reading the schematic correctly.

Also, most of the components were found in a XM301(there are 3 2n3904 transistors) and I had extra resistors laying around. I was going to gut a XM301 for a SIO2SD so the board was going to be useless anyway. I just had to find the 1uF capacitor for the sound. I just needed to get RCA jacks for sound and a perf board to keep things tidy.

Edited by Almost Rice, Thu Jul 3, 2008 2:26 PM.


#38 puppetmark OFFLINE  

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Posted Thu Jul 3, 2008 11:29 AM

The ghosting is more like an bright aura around images. If you play any game where you have a black background and lots of bright characters, you will see it. Robotron is one I see the ghosting(bright aura around the each image). Turning down the brightness on the monitor is what I do, but an internal solution would be best.

The sound was important to me because Needing to play Beef Drop, I had to join R5 and R6 puts all the signals together if I remember the reading the schematic correctly.


I see. I will check out Robotron. Changing R15 may help. I looked at the schematics and I think I can fix my audio with just a piece of wire (jumping the now open end of C11 to C14). Its essentially what you did except I am using the caps that are all ready on the 7800 board. I have a Ballblazer cart on the way so I can test my idea. I will look closely at the aura effect and see what I can come up with.

#39 Underball OFFLINE  

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Posted Thu Jul 3, 2008 12:04 PM

It's not 7800 sound that's the problem. It's POKEY sound. The 7800 sound effects are fine. But the few games that use the pokey for music - Commando, Ballblazer, Froggie, Beef Drop, have no music with yours.

Also - there's a bit of ghosting when the brightness is turned up enough. Think that 91k replacing R15 will fix that?

Oops! Now I understand. I don't have any of those carts to test. Where did you pick up the POKEY sound?

replacing R15 with a 91K will actually bring the brightness down a notch. I don't think it will help with ghosting. Many Atari systems have a slight ghosting problem due to the way the color signal is joined with the luminance signal. I guess Atari figured since the systems will work through RF anyway, the ghosting won't be noticed as the RF degrades the picture anyway.

When I hooked my 7800 up to a composite monitor and my TV and I don't think I noticed any ghosting but I will look again and see. I wasn't looking for any either, I was just amazed at how much better it looked. BTW, nice work on your 7800. Its good to have multiple people try something like this. Maybe we should call it the 7800 $10.00 super video Mod?


The ghosting is more like an bright aura around images. If you play any game where you have a black background and lots of bright characters, you will see it. Robotron is one I see the ghosting(bright aura around the each image). Turning down the brightness on the monitor is what I do, but an internal solution would be best.

The sound was important to me because Needing to play Beef Drop, I had to join R5 and R6 puts all the signals together if I remember the reading the schematic correctly.


Turning the brightness down does help, but on my TV, what happens is that other games are then negatively impacted. Particularly ones with colored/green backgrounds - specifically Commando. It doesn't make it terrible, but it's noticeably darker than it should be.


I'm really nitpicking here though. This mod is just plain awesome. It's cheap, and it takes all of 15 minutes to put together, even if you're a complete hack with a soldering iron.

#40 puppetmark OFFLINE  

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Posted Thu Jul 3, 2008 12:59 PM

Turning the brightness down does help, but on my TV, what happens is that other games are then negatively impacted. Particularly ones with colored/green backgrounds - specifically Commando. It doesn't make it terrible, but it's noticeably darker than it should be.


I'm really nitpicking here though. This mod is just plain awesome. It's cheap, and it takes all of 15 minutes to put together, even if you're a complete hack with a soldering iron.


No worries, any information is good. If we can change a couple of resistors or so to squeeze out an even better picture then I think that is worth trying. I always like simple solutions to seemingly complex problems and I am glad I can help provide one. I don't have a Commando cart but perhaps a 2600 pitfall cart shows the same symptom. If you have a pitfall cart, I would love to know that. Otherwise, I guess I will just have to buy a Commando Cart (like that is a bad thing!)

#41 Underball OFFLINE  

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Posted Thu Jul 3, 2008 2:59 PM

Turning the brightness down does help, but on my TV, what happens is that other games are then negatively impacted. Particularly ones with colored/green backgrounds - specifically Commando. It doesn't make it terrible, but it's noticeably darker than it should be.


I'm really nitpicking here though. This mod is just plain awesome. It's cheap, and it takes all of 15 minutes to put together, even if you're a complete hack with a soldering iron.


No worries, any information is good. If we can change a couple of resistors or so to squeeze out an even better picture then I think that is worth trying. I always like simple solutions to seemingly complex problems and I am glad I can help provide one. I don't have a Commando cart but perhaps a 2600 pitfall cart shows the same symptom. If you have a pitfall cart, I would love to know that. Otherwise, I guess I will just have to buy a Commando Cart (like that is a bad thing!)


Actually, I just redid the mod. My first go-round was sloppy, I didn't cut the tails on the resistors, so there was a lot of bending and folding going on. I just wanted to see if I could get it to work.

Also - Like I said, I couldn't find a 75 ohm resistor, so I made a 77ohm circuit putting a 47-10-10-10omh series connection. That was a pain in the ass, so I dropped one of the 10's to make it 67ohm.

Doing that, plus using a NEW solder roll as opposed to an old crappy one that was probably cold - the ghosting isn't really an issue now.

Pitfall looks fantastic.

I have a Cuttle Cart 2, so I can pretty much test anything.

#42 puppetmark OFFLINE  

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Posted Thu Jul 3, 2008 8:44 PM

Actually, I just redid the mod. My first go-round was sloppy, I didn't cut the tails on the resistors, so there was a lot of bending and folding going on. I just wanted to see if I could get it to work.

Also - Like I said, I couldn't find a 75 ohm resistor, so I made a 77ohm circuit putting a 47-10-10-10omh series connection. That was a pain in the ass, so I dropped one of the 10's to make it 67ohm.

Doing that, plus using a NEW solder roll as opposed to an old crappy one that was probably cold - the ghosting isn't really an issue now.

Pitfall looks fantastic.

I have a Cuttle Cart 2, so I can pretty much test anything.


Nice! I am glad you got it work better. I guess sometimes neatness counts-at least a little. ;)

I am jealous of your Cuttle Cart 2. I am still going to see If I can fix my audio problem. Almost Rice's way may be the best way to go, but I still want to al least try my idea.

#43 puppetmark OFFLINE  

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Posted Mon Jul 7, 2008 8:14 PM

*Update*

I fixed the POKEY Audio. All I had to do was run a wire from the top of C10 to the audio jack. I actually made the connection by running a wire from C10 to where the audio jack connects to the resistor I added for he audio.

Here is a picture of the wire:
Pokey_repair.jpg

Here is a close up of the connection at C10:
C10_connection.jpg

Here is a close up of where the POKEY audio meets the audio out:
Pokey_connection.jpg

Also, Changing R15 did very little to teh brightness of the video, BUT changing R11 from 39K to 47K seems to lower the brightness some. I didn't have to turn down the brighness as much and it seemed to help the aura effect on bright objects.

Here is where to find R11:
R11_replace.jpg

I am glad I got this to work. I hope others decide to try this. Its really not too hard and the results are well worth it.

Thanks again to everyone who helped.

#44 ApolloBoy OFFLINE  

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Posted Mon Jul 7, 2008 11:52 PM

Glad you were able to fix the POKEY issue. I was holding off on doing this mod until the POKEY issue was resolved. Are you going to update the instructions with the fix?

#45 puppetmark OFFLINE  

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Posted Tue Jul 8, 2008 7:05 AM

Glad you were able to fix the POKEY issue. I was holding off on doing this mod until the POKEY issue was resolved. Are you going to update the instructions with the fix?


Good Idea. I just updated the instructions (Post #14) to include the POKEY audio fix and the resistor change.

Edited by puppetmark, Tue Jul 8, 2008 7:06 AM.


#46 Underball OFFLINE  

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Posted Tue Jul 8, 2008 6:19 PM

*Update*

I fixed the POKEY Audio. All I had to do was run a wire from the top of C10 to the audio jack. I actually made the connection by running a wire from C10 to where the audio jack connects to the resistor I added for he audio.

Here is a picture of the wire:
Pokey_repair.jpg

Here is a close up of the connection at C10:
C10_connection.jpg

Here is a close up of where the POKEY audio meets the audio out:
Pokey_connection.jpg

Also, Changing R15 did very little to teh brightness of the video, BUT changing R11 from 39K to 47K seems to lower the brightness some. I didn't have to turn down the brighness as much and it seemed to help the aura effect on bright objects.

Here is where to find R11:
R11_replace.jpg

I am glad I got this to work. I hope others decide to try this. Its really not too hard and the results are well worth it.

Thanks again to everyone who helped.



Just did this. AWESOME. The glow/Halo around bright/white objects is gone. perfect.

I'm also getting really tire of pulling the metal sheilding off the mobo, and replacing it every time. what a pain in the ass that is.

Edited by Underball, Tue Jul 8, 2008 6:20 PM.


#47 ApolloBoy OFFLINE  

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Posted Tue Jul 8, 2008 7:25 PM

I'm also getting really tire of pulling the metal sheilding off the mobo, and replacing it every time. what a pain in the ass that is.


Just toss it. Once you get it modded, you don't really have any need for it anymore. I actually did this with some of my other systems and they work just fine.

#48 Underball OFFLINE  

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Posted Tue Jul 8, 2008 8:29 PM

I'm also getting really tire of pulling the metal sheilding off the mobo, and replacing it every time. what a pain in the ass that is.


Just toss it. Once you get it modded, you don't really have any need for it anymore. I actually did this with some of my other systems and they work just fine.


Is this true? puppetmark?

I suppose it makes sens the metal sheilding was to prevent interference from getting in the the RF... anyone?

#49 ApolloBoy OFFLINE  

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Posted Tue Jul 8, 2008 9:53 PM

Another question concerning the RF modulator; once all 4 pins are cut, is it essentially useless? I'd like to be able to remove it so I can have a bit more space to perform the mod.

#50 Underball OFFLINE  

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Posted Wed Jul 9, 2008 12:29 AM

Another question concerning the RF modulator; once all 4 pins are cut, is it essentially useless? I'd like to be able to remove it so I can have a bit more space to perform the mod.

I found that trying to remove the box tends to be a giant pain in the ass. It's got 4 mondo solder joints on the bottom of the board holding it in place. but I did snap the board sticking out of the back of it off to make the mod easier to work on.




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