Let's design a new video mod

[LittleJoe]

I was never 100% happy with the composite output, it never looked as nice as the rock solid s-video. I could see the TV I was using automatically adjusting the brightness as I turned the pots, and for a split second I 'd have excellent composite video, but then the TV would adjust making it too bright and washed out, and was forced to adjust the brightness down on the TV. This would reveal color clock skips in blues and other colors in composite, whereas s-video would be fine. Intuition told me that the sync signal was a little strong compared to chroma/luma, going into the fms6400 filter.

 

So I've made a small change the recent builds that I've done. I've substituted a 1.6K resistor in place of R3 which was 1.0k ohm. I also put 75 ohm output resistors on the composite, chroma and luma jacks per the applications notes for the FMS6400. Not really sure if the location makes a difference, but they appear to be right on the jacks in the application notes. Are they located there to reduce RF interference? The output resistors on Chroma and Luma aren't really needed, as far as I can tell, but installing them allows a single adjustment for Composite and S-Video.

[+batari]

I was never 100% happy with the composite output, it never looked as nice as the rock solid s-video. I could see the TV I was using automatically adjusting the brightness as I turned the pots, and for a split second I 'd have excellent composite video, but then the TV would adjust making it too bright and washed out, and was forced to adjust the brightness down on the TV. This would reveal color clock skips in blues and other colors in composite, whereas s-video would be fine. Intuition told me that the sync signal was a little strong compared to chroma/luma, going into the fms6400 filter.

 

So I've made a small change the recent builds that I've done. I've substituted a 1.6K resistor in place of R3 which was 1.0k ohm. I also put 75 ohm output resistors on the composite, chroma and luma jacks per the applications notes for the FMS6400. Not really sure if the location makes a difference, but they appear to be right on the jacks in the application notes. Are they located there to reduce RF interference? The output resistors on Chroma and Luma aren't really needed, as far as I can tell, but installing them allows a single adjustment for Composite and S-Video.

I think the 75 ohm resistors are supposed to be in the television itself for impedence matching the series resistors already on the board. If they are not in the television for some reason, having them on the board may help. But putting them on the board shouldn't hurt, either, as the chip is designed to handle two output loads. It will just run a little hotter.

 

So my suggestion is if the 75 ohm resistors help, use them.

[Ransom]

The 2002 ClearPic Mod has something to say about 75 ohm resistors which may be relevant:

 

By the way, if you want to hook up a stock Atari to a s-video TV or monitor, the Atari circuits are designed to be terminated with 75 ohm resistors. The old fashioned monitors had the option of using 75 ohm termination, but modern TVs do not. The result is an over-driven signal to the TV, which looks bad. So, if you want to hook an 800, for example, to a nice s-video TV, add 75 ohm resistors as terminators somewhere in the cable. Then it looks pretty good. You do not need this on ClearPic.

[supercat]

The normal way I've seen to drive video, including in circuitry designed for professional use, is to output a low-impedance signal twice as strong as desired, and then put a 75-ohm resistor in series. The net effect will be that the source impedance will be 75 ohms, the cable (if it's a good one) will be 75 ohms, and the destination impedance will also be 75 ohms. This will avoid reflections at the end of the cable which could otherwise cause ghosting. I don't think I"ve ever seen a video monitor which didn't have 75 ohm termination, though a few units did allow the termination resistors to be switched out.

[SoundGammon]

How would variable resistors work on the outputs of the CD4050? Setting them at the "stock" value and then turn each one to see what works best? Would that be easy to do, try and find pots with ranges in line with those resistors? Also, isn't there a buffer chip in the 7800?

[FullySicAtari]

Any chance for a PAL version when it is finished?

The circuit should work in PAL as-is. Connect pins 2, 5, 6, 7, 9, and 13 from the PAL TIA to the holes marked 2, 5, 7, 8, 9, and 13 on the board, respectively. Do not connect the holes marked 6 and 12. Then, omit R1, R2, R7, and C4.

 

Has anyone installed the mod in a PAL console using this method???

 

.....I have purchased some mods so when they arrive i will give it a go. Hopefully, if I don't blow-up my atari, I will post some installation pics to help others.

[retrofix]

I've been following this tread for quite a while now and am pleased to let all the PAL users know that a good working PAL 2600 mod is on its way and will be available for sale as of the beginning of April, 2012!

 

We are a small business operating in Victoria, Australia and will be offering all our modded systems for sale worldwide at www.retrofix.com.au. With over 2 years experience with console modification services and sales we have had much interest locally in finding a good 2600 mod so after a few months of testing and changes finally have what we believe to be an excellent clarity S-Video & Composite mod using the FMS6400CS.

 

My apologies if this seems like advertising but I just thought there might be a few PAL users hanging out for a quality working & available mod

[atari2atari]

I've been following this tread for quite a while now and am pleased to let all the PAL users know that a good working PAL 2600 mod is on its way and will be available for sale as of the beginning of April, 2012!

 

We are a small business operating in Victoria, Australia and will be offering all our modded systems for sale worldwide at www.retrofix.com.au. With over 2 years experience with console modification services and sales we have had much interest locally in finding a good 2600 mod so after a few months of testing and changes finally have what we believe to be an excellent clarity S-Video & Composite mod using the FMS6400CS.

 

My apologies if this seems like advertising but I just thought there might be a few PAL users hanging out for a quality working & available mod

 

That would be great!

 

I have a few 2600 PAL consoles that I have tried various video mods on, and I always get black and white output. This will be a welcome update.

 

You should post up in the "Marketplace" when your website goes live . . .

 

-a2a

[Amstari]

I've been following this tread for quite a while now and am pleased to let all the PAL users know that a good working PAL 2600 mod is on its way and will be available for sale as of the beginning of April, 2012!

 

We are a small business operating in Victoria, Australia and will be offering all our modded systems for sale worldwide at www.retrofix.com.au. With over 2 years experience with console modification services and sales we have had much interest locally in finding a good 2600 mod so after a few months of testing and changes finally have what we believe to be an excellent clarity S-Video & Composite mod using the FMS6400CS.

 

My apologies if this seems like advertising but I just thought there might be a few PAL users hanging out for a quality working & available mod

 

Will you be selling a DIY kit to modify your own console? Your website only seems to have consoles that have already had the mod installed.

Edited April 26, 2012 by Amstari

[omp]

Keen for a decent PAL composite mod as well. Have done the "simple" composite mod a few times for the video game store I work for, it looks ok for the cost of parts, but an improved mod would be the key.

[atariaddict82]

Are there .brd, .sch and gerber files available for the latest version of this board? I see towards the beginning of this topic there are gerber files; however, it seems that a lot has changed on this board since that post. I would like to have some boards printed, but would like to be sure that I have the most up to date files. Any help would be greatly appreciated!!

[Albert]

Greetings,

 

First, my apologies for not reading this entire thread. Can someone give me a summary of where this stands? I need several (5+) 2600 systems modified with s-video/composite/audio output to augment the modified systems I already have. I didn't have as many systems as I would have liked at the recent Portland Retro Gaming Expo.

 

Thanks!

 

..Al

[Game-Tech.US]

I need several (5+) 2600 systems modified with s-video/composite/audio output

 

I have a bunch of boards I designed from these schematics and I prolly have plenty of whichever console you want on hand including 6ers, woody and darth 4 switchers, Jrs, and Geminis.

PM me.

[Albert]

I have a bunch of boards I designed from these schematics and I prolly have plenty of whichever console you want on hand including 6ers, woody and darth 4 switchers, Jrs, and Geminis.

PM me.

 

I contacted LittleJoe and he's going to modify some systems for me, but thanks for your offer. It's good to know there are so many talented people in the classic gaming community.

 

..Al

[moonchilddave]

I was never 100% happy with the composite output, it never looked as nice as the rock solid s-video. I could see the TV I was using automatically adjusting the brightness as I turned the pots, and for a split second I 'd have excellent composite video, but then the TV would adjust making it too bright and washed out, and was forced to adjust the brightness down on the TV. This would reveal color clock skips in blues and other colors in composite, whereas s-video would be fine. Intuition told me that the sync signal was a little strong compared to chroma/luma, going into the fms6400 filter.

 

So I've made a small change the recent builds that I've done. I've substituted a 1.6K resistor in place of R3 which was 1.0k ohm. I also put 75 ohm output resistors on the composite, chroma and luma jacks per the applications notes for the FMS6400. Not really sure if the location makes a difference, but they appear to be right on the jacks in the application notes. Are they located there to reduce RF interference? The output resistors on Chroma and Luma aren't really needed, as far as I can tell, but installing them allows a single adjustment for Composite and S-Video.

 

I just bought and installed one of LittleJoe's boards (assembled)... I'm noticing the problems he mentioned here with the color being a bit washed out and having to adjust the brightness on the TV down real low. I assume this issue has not yet been solved? I went with composite as that is what my other systems use, and I have an auto switch that I'm using. The auto switch supports s-video and composite, but won't convert from one to the other, so I went with the lowest common denominator of all the systems - composite. Also, I like the look of a single jack for audio & video so I bought and used these:

 

http://www.probroadcastsupply.com/ctor-trrs-chassis-mount-snap-in-jack-grey-30-712/

 

http://www.amazon.com/gp/product/B000KW6VJ2/ref=oh_details_o00_s00_i00

 

Edited February 3, 2013 by moonchilddave

[+batari]

The mod started as a combination of the CD4050 mod from the AA FAQ, along with a copy of some of the 2600's own video circuitry, then run into a video filter/amplifier chip. I took another look at it all, removed/added parts by experimentation, and came up with my own mod. It looks pretty good in general, but I agree, the composite could be better. What seems to help is an additional 75 ohm load to ground on the composite line, but this "shouldn't" help in theory.

 

So I decided to redesign everything, literally everything, from scratch. I will take ALL TIA pins and lift them (no longer are we relying on ANYTHING on the 2600's board) and put them together to try and recreate a proper NTSC signal.

 

This is what I learned:

BLANK level is 0v

BLACK level is about 0.1v

WHITE level is 1.0v

SYNC pulse is -0.4v

COLORBURST is +/- 0.2v

AUDIO is about 1.4v RMS (??)

 

The negative voltages are a pain to produce and I don't think they are strictly necessary, so I shifted everything up by 0.4v. The circuit can be AC coupled to remove the DC offset if needed.

 

I have carefully chosen parts so I can get somewhat close to these values. I plan to simulate this circuit in PSPICE as well. I've also axed the CD4050... I really don't think it's necessary if this mod is done right and it actually makes some things worse. I used a pair of MOSFETs in a common-drain configuration to provide unity voltage gain but current amplification on both the Y and C subcircuits, then tied each to a load resistor. I expect that the output of the FETs should be "good enough" to produce a nice video signal on their own but I'll go ahead and run it through the filter anyway.

 

I'll post the new schematic after I have a chance to actually simulate in PSPICE, then build it and see how good it is, then tweak to try and match the actual NTSC spec as close as I can, and THEN connect to the TV and see how it looks. I don't have a solid timeline for this but if I do get somewhere, I'll post what worked.

[Uzumaki]

Is there a way to make AV mod that would squeeze the picture a bit so it'd retain 4:3 format on a 16:9 TV? My TV does not offer any option. And no I don't have the room for a second older TV. Either I get a 27" LCD TV or I get a crummy 15" LCD and 15" CRT.

 

The AV board I picked up off eBay is similar to Longhorn and with a little tweak on that 75 ohms issue I was able to get clean and ghost free image.

 

PS useful and must-do mod on pre-JR era 2600: LED for power on indicator. On the light 6 switch console I'm using, there's unused solder spot below the 5v regulator chip (7805) that has both +5v and ground. 200 ohms resistor and 3mm red LED on extra long wire and mounted to switch panel near the power switch.

[iesposta]

...

PS useful and must-do mod on pre-JR era 2600: LED for power on indicator. On the light 6 switch console I'm using, there's unused solder spot below the 5v regulator chip (7805) that has both +5v and ground. 200 ohms resistor and 3mm red LED on extra long wire and mounted to switch panel near the power switch.

 

Variation: Put the LED _in_ the switch!

[snstay]

Variation: Put the LED _in_ the switch!

thats cool did you have to drill through the switch to install the led?

[Uzumaki]

That doesn't look like standard 2600 switch. Interesting though but wouldn't using the switch a few times eventually break the wires to the LED?

[iesposta]

They kind of have lots of room to spring around and the throw is short:

[iesposta]

http://www.atariage.com/forums/topic/207471-atari-2600-led-power-switch/

This post has the video that gave me the idea, and more of my pictures.

[robertski]

That switch is rocking cool, Next I would add a pause circuit, and place the LED for it

inside the COLOR / BW switch, which I use for Pause, as I never switch into B/W mode anyways..

 

Keep on modding.

[alexlow8]

HI Guys,

 

I hope everyone hasn't lost intrest in this thread. I just got my assembled mod board from the electronicsentimentalities ebay store (ES), and just wanted to clarify a few things before I hooked it up, specificly what needs to be removed from my Atari board.

The online instructions form ES shows the removal of what appears to be R212 and C212 off the TIA Colour output (9) which appear to have the same component numbers on the PAL Rev. B board I have. The ES instructions also show lifting the 6, 9, 12 and 13 Pins on the TIA from the socket completely. As I see it, 9 is isolated once R212 and C212 are removed, so lifting this pin is unnecessary if the components are removed. 13 can also be isolated by removing R208 and C210. Pins 6 is LUM2 on the PAL TIA, and there is no BLK. Audio is single channel (No AUD1) and Pin 12 is used onfor the extra timing signal required for the PAL TIA.

The Rev. B board also has a CD4050 installed, which is connected to the CSYNC, LUM0-2 Pins on the TIA. I have been lead to believe that thes IC were not included on later boards, like the one used in the installation instructions provided by ES. This leads me to wonder if this component needs to be isolated fom the TIA.

If anyone can help I would greatly appreciate it. The TV in my gaming room has no analog tuner, so getting a quality mod working for my recently aquired 2600 is an absolute must.

[Rex Dart]

One thing I noticed is that you guys start with the FMS6400 right off the bat. Why is this? Looking at the datasheet, it appears to accept Luma and Chroma as inputs, and outputs... Luma and Chroma. I figure there must be some purpose, but can't figure it out.

 

I'm asking because I'm trying to add s-video to a picky Sega system (32x), and the only two options anybody's figure out so far are to either put up with blurry output, or this slapdash method that omits a lot of the existing video circuitry. Is there any possibility of the FMS6400 helping out here?