easier 7800 Composite video mod

[Dauber]

It's easier than you might think. Courage? If you ruin it, just get another one -- they're cheap enough.

[Lynxpro]

It's easier than you might think. Courage? If you ruin it, just get another one -- they're cheap enough.

 

Not on eBay recently. I've lost a bunch of bidding wars because I didn't want to go above $40.

 

Plus, a ruined console is one less console a future retro gamer could acquire to appreciate.

[Rex Dart]

I wish I had the skillz and the courage to mod my consoles like you guys...

 

 

Sounds like you're ready to learn, then. There's nothing to stop you but the purchase of a $10 soldering kit.

[reverendshoebox]

Funny you should say that...the biggest thing that held me back from modding was a $10 soldering kit. I had a crap soldering iron, and for years I screwed up everything I tried, ultimately leading me to the conclusion that I completely sucked at soldering. But eventually I decided to blow $40 on a Aoyue soldering station and it's one of the best investments I've ever made.

 

That said, maybe I do completely suck at soldering and having a good iron just lets me get by with less skill. Either way, I'm happy with the result.

 

-=ShoEboX=-

[Rex Dart]

Maybe the wattage was just wrong. Too much or too little and you're either slightly warming, or burning holes in, PCBs.

[thecrypticodor]

I just recently did this mod on my 7800. I left the 75 ohm resistor out of the circuit when I noticed removing it just about eliminated the majority of the ghosting issues that others have also described.

Also some posters in this thread have inquired about leaving out the RF shielding. Although I noticed no difference in 7800 games with it out. I noticed a lot of distortion and noise in the 2600 video that cleared up when I put it back on. So it you definitely still need it even without the modulator.

 

These pictures were taken off an LCD so it should look even better on a crt. The brightness does seems to be a little intense which washes out the colors a little. All and all I'm pleased with the results.

Edited January 15, 2014 by thecrypticodor

[SnapCraft]

OK, so I've been working on this mod for a while. I didn't find it that easy. I have a question though. I was testing it on my LCD TV and wasn't getting a picture, so I tinkered with it for a long time. Finally I tried it on my CRT and, wow, it worked. I get an dark picture, but it works. Can someone explain in "stupid" language why it works on a CRT but not a LCD.

 

Logically it makes no sense--it's a video signal. In my mind I can't figure out why a plug-in-play "game" works on both, but not a mod like this?

[ColecoGemini]

OK, so I've been working on this mod for a while. I didn't find it that easy. I have a question though. I was testing it on my LCD TV and wasn't getting a picture, so I tinkered with it for a long time. Finally I tried it on my CRT and, wow, it worked. I get an dark picture, but it works. Can someone explain in "stupid" language why it works on a CRT but not a LCD.

 

Logically it makes no sense--it's a video signal. In my mind I can't figure out why a plug-in-play "game" works on both, but not a mod like this?

The Frequency/signal that the 7800 outputs isn't "standard". Although CRT's tolerate these analog signal variances as a rule, LCD and other modern TV platforms aren't always as tolerant. It varys by brand, and by TV Type. What you are seeing is not uncommon.

[ColecoGemini]

I just recently did this mod on my 7800. I left the 75 ohm resistor out of the circuit when I noticed removing it just about eliminated the majority of the ghosting issues that others have also described.

Also some posters in this thread have inquired about leaving out the RF shielding. Although I noticed no difference in 7800 games with it out. I noticed a lot of distortion and noise in the 2600 video that cleared up when I put it back on. So it you definitely still need it even without the modulator.

IMG_0244.JPGIMG_0198.JPGIMG_0220.JPG

IMG_0217.JPGIMG_0202.JPGIMG_0228.JPG

 

These pictures were taken off an LCD so it should look even better on a crt. The brightness does seems to be a little intense which washes out the colors a little. All and all I'm pleased with the results.

locate the 7800 Chroma and 2600 Chroma Resistors on the resistor ladder and double the current values - 4.7k to 9k and 4.3 k to 8.5k or there abouts. It punches the color right up and cuts down on the blue blur/ghosting as well, tightens it up nicely. looks especially good on PAc MAn Collection and Pole Position II where there are very thin lines/lettering.

[MGustafson]

Just finished this mod, cut out R3 and pulled audio straight from between the two resistors shown elsewhere on here. Used the floppy power connector trick also. I put the two plugs facing down on the back left side of the conssoe and used the three resistor setup off the transistor, made it into a nice little bundle. Only change I really made is the two resistors to ground connection. I ran a wire from them to the ground on the video jack with the assumption that grounding the video amp circuit to the video jack would create a little better ground.

 

Had an issue at first with no video, but realized it was that the floppy power jack fit slightly loose, I put a bend in the pins that it's on and voila, much better connection.

 

The video issue had me panicked, but after I wiggled it the signal came through the tv just fine.

 

It works wonderfully on both my 32 inch lcd AND on my 65 inch that's mounted in the living room. Very slight ghosting, but I took a lot of care soldering the transistor connections and trimming excess leads of AFTER soldering. My first run had some slight color issues and more ghosting, but I went through my connections and found a couple sloppy spots I cleaned up with side cutters and a knife.

 

Must say the playing this on our living room TV is quite the treat.

 

I think next time I will try to add a quick disconnect to the audio wire, plus put the amp circuit on a small board that I can mount in the groove on the left side. I'm planning on keeping the jacks mounted to the case, which is the reason for the disconnect so basically if I have to tear it down or if the board dies for some reason, I can reuse the mod in another console with only about 10 minutes worth of work.

 

All in all I'd say this was a 3 out of 10 in difficulty, and that's with my lackluster soldering skills, but everything is VERY easily done and I already have people wanting me to do it for them.

 

Buy yourself a resistor kit so you don't have to scrounge, a dual wattage soldering iron (mine is a 20/45 or something around that) and a bag of the transistors, once your friends see it work on a modern TV they'll be wanting one two so you can probably make your money back on the equipment in no time. I spent about $25 and the resistors work a work write off since I use them all the time there.

 

Now my next steps will be replacing the power (I want to experiment with a USB power source from a phone charger) plus a LED swap and probably a custom badge for any consoles I work on. Then on to the controllers.

[+-^CrossBow^-]

I thought I was pretty good at doing this stuff....but... long story short, I've spent half the day trying to get this 'simple' mod up and going and just get a blank screen with audio cutting out. I used Moon Patrol as the test on the audio and it would only play about every other note. I finally had to give this up and just restore everything back the way it was.

 

Odd because I've done the 5200 s-video mod, Genesis s-video, even installed the LHE AV upgrade on another 7800. Those should have been more difficult right? I even tried to make the circuit on my breadboard again without any success at all?

 

If it is at all possible, can I please have someone take a much better pic of their circuit layouts they came up with? The schematic is actually very confusing to me as it all looks like it should short itself out to me. Obviously it doesn't but still. And I followed the process on post #14 except that I was putting everything onto perf board to make it look nicer.

Edited May 21, 2014 by -^Cro§Bow^-

[+-^CrossBow^-]

Update...

 

So.. I rebuilt the circuit making sure all connections were good per the schematic and guess what? Nope...no video... but as I predicted it is all shorting out because the 2222 literally burnt itself up?! I then redid the circuit taking out everything that is connected to ground so that I just had the 2.2k off the +5 to a new 2222, the video in to the 2222 and of course video out from the 2222. Still nothing and again the 2222 burnt itself up?

 

So.. I then pulled out the very very very simple schematic for outputing composite from a model 2 genesis. It only uses a 220uf cap from the video in to a 68 - 75k resistor to the video out. And I have a composite picture! So I'm curious why the transistor is even needed to do this if amplifying the signal isn't needed?

 

I also redid the circuit using just the 2222 and only a 68k resistor to the video out. This also seems to work just fine and produces a much smoother overall picture than just the cap and resistor did by themselves. I'm going to go with that as the picture is better than my LHE AV modded composite is and doesn't have the horrible bleeding I get with that mod.

 

Now if I could just figure out the audio issue...

 

Can someone correct me if I'm wrong on this? But for the audio on the LHE mod you just have to cut the north legs off of r5 and r6 closest to the back of the PCB and solder them together. From that solder point you run a cap to the audio out rca? Again I'm curious why a resistor is needed in the circuit on the mod in this thread.

 

Also I don't know if any of this makes a difference, but I did not cut the rf modulator lines as I was hoping to still keep the RF portion intact in case it was still needed.

 

Ideas on any of this?

[+-^CrossBow^-]

Sorry but it won't let me edit my previous posting so...

 

Anyway, I rebuilt the circuit exactly as the schematic. And I figured out where my issue was before. Long story short, this is working just great! While the capacitor /resistor only connection does work, I noticed that this circuit with the extra resistors cuts out the jailbars that the LHE produces and also that I was getting with the capacitor/resistor only connection.

 

So it works great but the audio wired up like it is in post #14 produces the opposite effect of the LHE mod. The LHE mod creates a really soft pokey with the TIA sounds overpowering if you wire it as the common instructions tell you to. With this mod the Pokey is really overpowering the TIA now. I'm going to keep it as it for the night, but will likely pull r5 and r6 off the board on the north connections and attach the audio from there. Again when I was doing this last night in that manner, I was getting audio that was cutting in and out constantly, likely another part of the circuit that was wired wrong could have been causing that.

[Shawn]

nm I had the wrong resistor value.

[Shawn]

Anyone successfully used a 9013 instead of a 3904 transistor?

[Shawn]

I see a couple of sellers on ebay with this mod but without any resistance on the emitter? How is that possibly gonna net clean video? Is adding the 65 to 75 ohm resistor there overkill? I myself found some ghosting without it. Here are pics of the boards in question:

 

 

As you can see neither have anything but a grounding off the emitter.

 

 

[bigbacon]

I see a couple of sellers on ebay with this mod but without any resistance on the emitter? How is that possibly gonna net clean video? Is adding the 65 to 75 ohm resistor there overkill? I myself found some ghosting without it. Here are pics of the boards in question:

 

$(KGrHqZHJCQFBSjFi+2mBQWqpV1v4!--60_57.JPG$T2eC16RHJFoE9nh6nwt1BQ)Q2bsiBg--60_57.JPG

 

As you can see neither have anything but a grounding off the emitter.

 

 

 

i would like to know as well how to fix the ghosting. My mod board is like the one pictured on the left.

Edited November 6, 2015 by bigbacon

[bigbacon]

I see a couple of sellers on ebay with this mod but without any resistance on the emitter? How is that possibly gonna net clean video? Is adding the 65 to 75 ohm resistor there overkill? I myself found some ghosting without it. Here are pics of the boards in question:

 

$(KGrHqZHJCQFBSjFi+2mBQWqpV1v4!--60_57.JPG$T2eC16RHJFoE9nh6nwt1BQ)Q2bsiBg--60_57.JPG

 

As you can see neither have anything but a grounding off the emitter.

 

 

 

hey, someone on 7800 facebook group told me to just move the board outside the RF shielding...Tried it and BAM, no more ghosting using one of these cheap boards.

[R.Cade]

I've done this mod before, and other slight variants on various models of 2600. However, on the 7800 the chroma is very weak... the colors are faded unless I turn the color way up on the monitor. Everyone else's color is properly saturated with this mod? Or is the 7800 just a less colorful design.

[R.Cade]

I've done this mod before, and other slight variants on various models of 2600. However, on the 7800 the chroma is very weak... the colors are faded unless I turn the color way up on the monitor. Everyone else's color is properly saturated with this mod? Or is the 7800 just a less colorful design.

 

It helps 2600 games to bridge TIA pins 6 and 9 with a small resistor. I used 200 ohm... I think on the older schematics it's 820. 200 gives you more saturation at the expense of a little color bleed.

[alortegac]

I was wondering, Has anyone seen the mod with audio attenuation? It looks the same + a 18k resistor + elect. cap?

 

Sold in EBAY as Atari 2600 & Atari 7800 AV Composite Mod Kit with Audio Attenuation Mod. by silverfox0786.

 

I have done several mods on 7800's using the "vintagegamesandmore" kit including the POKEY step adding a 6.8k resistor to reduce the main AUDIO output and balance it a bit better (not always needed). I have also used a pot instead of a resistor. They sound great, so what is this audio attenuation?

 

On a second topic, in some occasions, I have noticed some background noise, like buzzing sound, specially noticeable at higher volume in moments of silence, when there is no other background audio, for example the first screen in POLE position. I noticed that it can be mitigated by using good quality composite cables, but there is always some minor noise.......any suggestions on how to filter/clear the noise? is it coming from the power supply?

 

thanks for your feedback!

Edited February 3, 2016 by alortegac

[Shawn]

I thought it might be worth adding that an s9018 transistor (usually used in AM\FM audio amplification) will work perfectly in place of a 2222 or 3904 if you don't have either of those.

 

[Shawn]

[jum]

Hi, I have just done this mod on my PAL 7800 (rev C), using the video amp circuit from phoenixdownita ( http://atariage.com/forums/topic/127926-easier-7800-composite-video-mod/?p=2813736 ) and followed this guide for the rest: https://www.thefuturewas8bit.com/index.php/7800_comp_mod

I had to reduce the resistor on the video output to 20 ohm (else my CRT wouldn't pick up the colour, and my capture card wouldn't pick up anything).

Re-used the modulator's RCA connection for video, put the video amp circuit inside the modulator box.

Video quality seems OK, slight ghosting, but much better than RF quality.

Also put a 2200 ohm resistor on the audio output, but it's still very loud, maybe 4700 ohm would be better.

Edited October 10, 2017 by jum

[Pbrook67]

*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.

 

So you got the POKEY to work doing it this way????? I REALLY need to know.... I am having that issue.... No sound form a POKEY game...