159 replies to this topic

[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]

LittleJoe, on Wed Feb 29, 2012 1:01 PM, said:

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:

Quote

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]

batari, on Tue Apr 5, 2011 1:59 PM, said:

Thomas Jentzsch, on Tue Apr 5, 2011 5:16 AM, said:

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]

retrofix, on Thu Mar 22, 2012 9:57 PM, said:

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]

retrofix, on Thu Mar 22, 2012 9:57 PM, said:

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 by Amstari, Thu Apr 26, 2012 6:12 AM.

[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.