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No color after composite mod


jacl3

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Put the 15 in place of the 22 and got the same result just black and white. Am starting to think it might be the amp as Osgeld suggested, I may leave it like this till I get Osgelds driver to swap in unless you guys have another idea for me to try.

Edited by jacl3
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Put the 15 in place of the 22 and got the same result just black and white. Am starting to think it might be the amp as Osgeld suggested, I may leave it like this till I get Osgelds driver to swap in unless you guys have another idea for me to try.

Yeah may be, I'm all out of ideas now I thought for sure that was going to be it after seeing the video with it jumped. Sorry you went through all that for nothing.

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I'm having fun with the project to be honest,

 

ya know that's the key right there, dont let it become unfun, sometimes that requires taking a step back, you will get it, and you will enjoy doing it and the results

Edited by Osgeld
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I played Frostbite for a while with the 15pf in and the video began to bounce (up and down but not rolling) as it did when I had the 75ohm resistor between ground and video out. Both of you guys have been awesome so far with the suggestions. I put back the 22 and it no longer bounces. The games are still playable in black and white so at least there is that. Maybe it is just something with my driver circuit as you suggested.

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I dont think you did anything wrong, but those transistor amps require fiddling to your specific unit, so does mine but its more of "oh its too dim or bright change the 1 resistor and be done with it" but for all atari 2600 models that resistor is 1.5k

 

where as a coleco gemini wants like 1k and a 7800 wants 2.2k, point is im not trying to bias a transistor on a passive resistor mixer to be in spec to be 1/3rd of a 0.7 volt signal, might as well be blind without a scope, screw that im buying the 56 cent chip and 10 bucks for 100 pcb's custom made from china heh

 

maybe not the most economical way for a home hobby guy wanting to do 1 system, but I do enough 2600 mods that it saves me money to do it that way

 

I dont want to give away every board I make, they do cost money, but I dont mind helping someone out who is having fun and putting effort into trying, and its not like I am using some magical special circuit, its copy paste direct from the datasheet lol

Edited by Osgeld
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I agree about the amp circuit Osgeld. I had similar issue but mine was a TV wouldn't even recognize the signal at all. One in living room did but not my other one. Video out was only 200mV peak to peak with the mod. Swapped out the 2.2k and 3.3k ohm for 4.7k and 6.8k and then it recognized the signal and played fine. Signal still not where I wanted it though as a video signal should be around 1V Peak to peak and I was getting 600mV after swapping the two resistors so not sure if there would still be compatibility issues with other TV sets. I tried changing just one resistor value didn't make any difference couldn't get above 600mV p-p due to colors started bleeding when I went higher resistance values. After playing with pots in place of the two resistors on mine while watching my oscilloscope I felt I had the highest signal and best looking picture when I just doubled both the resistor values.

 

Anyways yeah that is probably a similar issue here as well, just maybe his TV isn't recognizing the color burst because the video output is too low but is able to see the rest, and by bypassing the 22pF cap it strengthened that part just enough for the amp to push out a little more for the TV to recognize it but wasn't smooth due to cap being bypassed but at least explains why he had good color(although not a smooth picture due to cap being bypassed) when he jumped the cap.

 

Either way i agree with Osgeld on what the issue was. You could try changing the resistor values if you have them but I wouldn't go out and get them if Osgeld is already sending you something to replace the mod with. Glad you had fun working on it too.

Edited by SignGuy81
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Osgelds circuit arrived today, I soldered up leads and put it in my console with my breath held, unfortunately it is still in black and white, but much brighter than it had ever been before.

 

He also suggested swapping another capacitor so I tried with and without swapping that.

 

Following SignGuy81s suggestion, I put in a 4.7k and 6.8k, still black and white!

 

I went out and got two 10K potentiometers and wired them back to my original circuit and I was able to get it in color! The video is not very bright but it still works though, my guess is something else is wrong/has been swapped at another time in this console.

 

I am keeping my eyes out for another 2600 as this one is not in the greatest external condition but I have had tons of fun working on it so far.

 

Just wanted to keep you guys posted.

 

For the record this is a Rev 5 board.

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I just posted a bunch of garbage so I edited to remove. Been a long day. Can't figure out how to remove that pic below but that isn't for your board.

 

Ah darn haha I saw the post on my email and I opened the browser hoping to find a solution!

 

I bought the Atari off Kijiji just a week and a half ago so I don't know if the board is the original from the case, the case says CX2600A but the board says 1980 Rev 5

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Due to the way that it acted when you jumped C209 it is if it helped increase the signal and gave you near perfect color and picture other than the jaggedness like you described I would think it is still something on that color burst line that is the problem. I would try swapping out that 47pF cap too on that line and see if that does anything. It is C210.

 

 

EDIT:

It is like the signal is week for some odd reason on that particular line coming out of the TIA before the signal gets mixed. This is why I suggested the larger resistor values which helps increase the signal going into base of transistor but apparently those still weren't enough to boost that particular part of the signal, but then you put the 10k pots in, not sure exactly where you have them set but larger resistance helped increase the signal enough to get you your color.

 

So here is what I'm thinking. If the 47pF cap isn't the issue, that I'm wanting you to try then instead just take out the 6.8k ohm resistor(R210) and replace it with a lower value, I'd say 4.7k ohm that you have, and if that doesn't do it then go down to 3.3k ohm. But try both of those for R210 on board and see if that helps. Some odd reason that particular line is weak.

 

EDIT 2:

If you verify same problem after swapping out both caps on that line, and also that you have a 5V signal going by the schematic on R220 and R211(both 1k ohm resistors) on the 5V side going by the schematic.then I would suspect a problem with the TIA chip but you could also do an ohms check on all the resistors on that line to be sure they are okay. But as long as it is still producing a signal but just weaker just lowering that 6.8k ohm resistor may make it work.

Edited by SignGuy81
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Ah darn haha I saw the post on my email and I opened the browser hoping to find a solution!

 

I bought the Atari off Kijiji just a week and a half ago so I don't know if the board is the original from the case, the case says CX2600A but the board says 1980 Rev 5

Maybe have a solution now. Check above ^

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I got it!! I put a 75 ohm between the video out and ground and kept adjusting the two pots until it looked right, without the resistor it kept bouncing, I felt like I was playing with the vertical hold on an old TV but I finally got it locked!!

 

Without the 75ohm I managed to find a place where the color looked good but couldn't get it to stop bouncing no matter how fine I played with it.

 

Sometimes I had it working on some games but not other, finally the right balance!!!

 

 

Thank you guys so much for all the suggestions, now time to expand the collection :D

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glad you got it working

 

Can you do an ohms check on your pots and get back with what values you had to use for each. Also even though you still got it working, it should have worked with Osgelds board so something still may be iffy with it but as long as you got it that is great! :)

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glad you got it working

 

Can you do an ohms check on your pots and get back with what values you had to use for each. Also even though you still got it working, it should have worked with Osgelds board so something still may be iffy with it but as long as you got it that is great! :)

 

Ok so the 3k3 has been replaced with a 1k8

 

And the 2k2 and been replaced with 11k2 (I truly though 10k pots only went to 10)

 

I de-soldered the pots to check their values so they were isolated from the circuit.

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Sorry to keep replying to myself, it seems I can only edit for a few minutes then I lose the ability. Either way reading closer on Ben Heck site I just noticed he says "And that's it! So simple even I can do it! Remember you'll still need to hook up the Atari 2600's color delay potentiometer, which basically lets you set the picture's tint (but without it you're in black & white land). Rewiring that thing is covered in my book.".

I guess it is more of an advertisement for his book, leaves me a bit disappointed.

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Ok so back to the drawing board, the 5 games I played yesterday worked pretty well some games still bounce uncontrollably, I am thinking that I will do Ben Hecks composite video Rev 2 as found here http://benheck.com/book/support/Atari2600VidMod.htm

 

Honestly I don't think any mod is going to to help until you find the underlying problem. The 2 resistor & transistor mod isn't working, and also the board that Osgeld sent you. The problem seems to be before the signal is picked up by the mods you are trying. Unless maybe you do a mod that picks up everything directly from the TIA and has it's own resistors and such which may bypass whatever problem is on the board but I don't know of a mod that does that completely. I do know of one that does partial though which is Longhorn's mod in which case you do have to lift pins 6 and 9 of the TIA and connect directly to those, which may be a good thing because I believe still there is a problem after pin 9 of the TIA or the TIA itself.

 

Can you try to get everything back to the normal 2 resistor, transistor mod except put in 4.7k and 6.8k ohms, and then put one side and the wiper of your 10k pot in place of the 6.8k ohm on your Atari main board at R210 and set it for 6.8k ohm first but then lower the resistance down while hooked up and see if that does anything?

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I tried cutting the resistance of R210 down to 3k3 earlier today with no success, also checked and am getting 5V where I should.

 

I'm really not sure what is going on here but I am getting very disheartened at this point haha.

 

The ben heck mod ties directly to pin 2 (CSync) 5 (Lum 1) 7 (Lum 2) and 8 (Lum 0) off the TIA and adds its own resistors, it gets Chroma from a mystery spot, but this page here ( to get Chroma from between C210 and R210

AudioChromaHookup.jpg

 

 

You tie in to TIA pin 2 5 7 and 8 directly by removing resistors 216, 215, 214 and 217

Video_Mod_2005_2.jpg

 

as he shows here, they go straight to the TIA from there

 

Type_B_traces.jpg

 

My board looks the same as that on the back, I confirmed they go straight to the TIA.

 

This was his old mod

VideodiagramX.jpg

 

This is his new mod

Video_Mod_2005.jpg

 

I am thinking I will connect the Chroma wire here where I put the dot

wBFKSgP.png

 

Honestly though at this point I'm feeling like the project is becoming hopeless, until tomorrow.

Edited by jacl3
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I see what he did there, yeah he got the signal from between the C210 and R210 which means he tied into it before the resistance(keeping in mind that C210 and R210 are reversed by mistake in the FSM schematic) so thus the signal there would be stronger, which would be needed without a transistor just as shown in the original mod schematic, no transistor. Since you are doing the transistor mod and tying this signal into the base of the transistor if you connect wire from that same spot between C210 and R210 since before the resistor the signal will probably be way to strong.

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Honestly I don't think any mod is going to to help until you find the underlying problem. The 2 resistor & transistor mod isn't working, and also the board that Osgeld sent you. The problem seems to be before the signal is picked up by the mods you are trying. Unless maybe you do a mod that picks up everything directly from the TIA and has it's own resistors and such which may bypass whatever problem is on the board but I don't know of a mod that does that completely.

 

Bryan's UAV mod does that - I'm installing one in a 2600 (4-switch Woody) this weekend.

 

http://atariage.com/forums/topic/246613-new-video-upgrade-coming-soon/

 

http://atariage.com/forums/topic/260267-the-uav-rev-d-video-upgrade-thread/

 

He's just moved back to the U.S. and I don't think has any boards to sell, but has indicated he has ideas for further improvements. I have 4 of his boards now (two of the earlier Rev C and two of the more recent Rev D). All are in use or destined for use in my machines. The one I'm installing in the Woody is a Rev C.

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Bryan's UAV mod does that - I'm installing one in a 2600 (4-switch Woody) this weekend.

 

http://atariage.com/forums/topic/246613-new-video-upgrade-coming-soon/

 

http://atariage.com/forums/topic/260267-the-uav-rev-d-video-upgrade-thread/

 

He's just moved back to the U.S. and I don't think has any boards to sell, but has indicated he has ideas for further improvements. I have 4 of his boards now (two of the earlier Rev C and two of the more recent Rev D). All are in use or destined for use in my machines. The one I'm installing in the Woody is a Rev C.

 

 

I might try that one eventually, I'm getting another Atari tomorrow after work to play with. I didn't realize the newer Ben Heck mod tied directly to the TIA(while also removing resistors on board to eliminate any problems backfeeding) until I seen the schematic he showed above as I've never tried that. Hopefully a mod that does that whichever one he tries will bypass whatever problem he has on the board. If not would you agree with possible bad TIA?

Edited by SignGuy81
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I am also strongly considering doing this mod here tomorrow

pic_5.png

 

A bit more complex but not that bad

Just need to find the best place to grab pin 9 I guess

Since it has it labeled as TIA colour on the board I would think you would tie it directly to pin 9. Does this board also have a schematic that goes with it?

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