No color after composite mod

[jacl3]

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?

I'd rather grab it off the board to avoid risking heating the TIA, I think I'm going to build this circuit rather than the Ben Heck one as this gives svideo which can be easily combined to make Composite (svideo will probably look better anyway) and also goes straight off the TIA so I can avoid any other issues on my board.

 

 

 

If this mod doesn't work then yes, bad TIA for sure.

Edited May 12, 2017 by jacl3

[SignGuy81]

I'd rather grab it off the board to avoid risking heating the TIA, I think I'm going to build this circuit rather than the Ben Heck one as this gives svideo which can be easily combined to make Composite (svideo will probably look better anyway) and also goes straight off the TIA so I can avoid any other issues on my board.

 

 

 

If this mod doesn't work then yes, bad TIA for sure.

 

 

Yeah I would go with that one too. When I said straight from the TIA I meant electrically, not physically. So yeah, what I would do is just follow the schematic, first component connected to pin 9 remove it and then connect your wire and solder to the side going to the TIA. May have to remove 2 or more components on the lines you will be connecting to. I looks like for the TIA pin 9 you would remove R220 and C210 to isolate that pin.

[+DrVenkman]

 

 

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?

 

So to follow up with my comment the other day ... yes, I'd suspect a bad TIA - I say that now, because having installed the UAV board into my 4-Switch Woody that I *thought* had a bad RF modulator, I still had a crappy pictures, messed up colors, bad contrast and - tellingly - screwy display of Activision games with the rainbow logo and sunset skies. Swapped TIA with one from another machine and it looks great now.

 

So yeah, I think next step for the OP is to try swapping TIA and see how it goes.

[Osgeld]

not to toot my own horn

 

 

but if you didnt get color using my av board, then yes there is something else going on, cause that thing is the simplest circuit (even though its super complex in the chip itself) to get ttl signals into NTSC / Pal voltage spec's which is what all the various mod's more or less do

 

I dont think you have a bad TIA, but you might have a failing TIA, but you could have something else failing as well

Edited May 13, 2017 by Osgeld

[jacl3]

not to toot my own horn

 

 

but if you didnt get color using my av board, then yes there is something else going on, cause that thing is the simplest circuit (even though its super complex in the chip itself) to get ttl signals into NTSC / Pal voltage spec's which is what all the various mod's more or less do

 

I dont think you have a bad TIA, but you might have a failing TIA, but you could have something else failing as well

 

I am going to try to get another 2600 to install it on in the future, I am sure it works, I guess something must be messed up on my console.

 

I am also still planning to build that other Svideo circuit I posted here earlier, I am just having a hard time finding some of the resistor values locally and don't really want to do it with a ton of series resistors

Edited May 15, 2017 by jacl3

[SignGuy81]

 

I am going to try to get another 2600 to install it on in the future, I am sure it works, I guess something must be messed up on my console.

 

I am also still planning to build that other Svideo circuit I posted here earlier, I am just having a hard time finding some of the resistor values locally and don't really want to do it with a ton of series resistors

 

I can't remember but did you ever mention if you tried the Atari on a different TV? Also what brand and model are you trying it on?

[jacl3]

I tried it on 2 different tvs, one is a Sharp and one is a Dynex (Best Buy house brand) both are LCD tvs. On the Dynex it seems to only work some times, if I turn it on and off a bunch of times. On the Sharp I get picture always but with the results explained above.

 

I think part of it is the TV and it refusing the go color for a non perfect signal. But I have no room for a CRT

[SignGuy81]

I tried it on 2 different tvs, one is a Sharp and one is a Dynex (Best Buy house brand) both are LCD tvs. On the Dynex it seems to only work some times, if I turn it on and off a bunch of times. On the Sharp I get picture always but with the results explained above.

 

I think part of it is the TV and it refusing the go color for a non perfect signal. But I have no room for a CRT

 

I believe your assumption is exactly correct about the signal being to weak. I don't think there is a problem with your Atari now(pre mod components, especially seeing as it worked fine before the mod).

 

When I first modded two 2600s they worked perfect on my Hisense but not on a GPX. I increased the values like I asked you to do and it worked on the GPX, but the signal was still too low for a standard composite signal which is supposed to be 1V peak to peak while instead I had 600mV peak to peak. While both my Ataris play now on the GPX I bet if I hooked them to your Sharp or Dynex I'd have the same problem you do. I probably just increased my TV compatibility a little by increasing the resistors but need to keep working to get the basic composite mod a 1V peak to peak signal(that is also a good clean signal) all TVs can use.

 

Here is a post by another user, with a Sharp who may have the exact same issue that I've been trying to help as well. http://atariage.com/forums/topic/265301-composite-video-mod-whats-wrong/

 

I just gave him an update today as well if you want to take a look at it.

Edited May 16, 2017 by SignGuy81

[jacl3]

 

I believe your assumption is exactly correct about the signal being to weak. I don't think there is a problem with your Atari now(pre mod components, especially seeing as it worked fine before the mod).

 

When I first modded two 2600s they worked perfect on my Hisense but not on a GPX. I increased the values like I asked you to do and it worked on the GPX, but the signal was still too low for a standard composite signal which is supposed to be 1V peak to peak while instead I had 600mV peak to peak. While both my Ataris play now on the GPX I bet if I hooked them to your Sharp or Dynex I'd have the same problem you do. I probably just increased my TV compatibility a little by increasing the resistors but need to keep working to get the basic composite mod a 1V peak to peak signal(that is also a good clean signal) all TVs can use.

 

Here is a post by another user, with a Sharp who may have the exact same issue that I've been trying to help as well. http://atariage.com/forums/topic/265301-composite-video-mod-whats-wrong/

 

I just gave him an update today as well if you want to take a look at it.

So you're suggesting swapping out R222 from the 15k to something smaller? Maybe the 4k7? Then I can try with the pots to see if I can get a stronger signal?

[SignGuy81]

So you're suggesting swapping out R222 from the 15k to something smaller? Maybe the 4k7? Then I can try with the pots to see if I can get a stronger signal?

no, that was if using for example the earlier mentioned 4.7k and 6.8k was that I was off when trying to keep the ratio about the same as the 2.2k and 3.3k and was because the 15k was on the main board in parallel where the 3.3k was so it threw me off completely when I was trying to keep the ratio the same, instead I should have tried for as if I had 2.2k and 2.7k(2.7k is around what you have with 3.3k and 15k in parallel). So that basically meant that what I needed if I had 4.7k in the spot of 2.2k I should have instead went for 5.6k on the other one(and would have to desolder the 15k if putting in a 5.6k ohm resistor, or instead leave it in place and use a 9.1k(9.1k and 15k in parallel would be around 5.6k).

 

It basically would be like you doing the first thing I asked with the 4.7k and 6.8k ohm but instead of using the 6.8k you would put in a 9.1k ohm. This may increase the signal slightly but I'm not sure if it would be enough. Also the other thing I told him to try if it still doesn't work is to take out the 15k and then for the mod board try 6.2k where the 2.2k goes and 9.1k where the 3.3k goes.

Edited May 16, 2017 by SignGuy81

[SignGuy81]

So you're suggesting swapping out R222 from the 15k to something smaller? Maybe the 4k7? Then I can try with the pots to see if I can get a stronger signal?

 

I tried to think of the simplest solution to get a stronger signal to work for you and the other guy.

 

Going back to the 2 resistor/transistor mod what I did was just completely eliminate the 3.3k ohm resistor altogether on the mod board(like I say there is a 15k ohm resistor across that same path and trying to use higher values anyway so will just let this be the value for that one) and for the 2.2k ohm resistor put in a 10k ohm or slightly higher. I used 10k ohm because it was the easiest to find in my junk pile that I need to get organized. I then hooked my scope to the output while playing game and I had an 800mV peak to peak signal this time, the highest I've had. With my previous resistor adjustment I had 600mV peak to peak.

 

Doing this may very likely bring you color. All it is is putting the mod board back on and changing out the resistor(the one that is supposed to be 2.2k) with a 10k and then removing the other resistor(the one that is supposed to be 3.3k). That simple and gives you much stronger signal.

Edited May 16, 2017 by SignGuy81

[jacl3]

Well I realize it wasn't what you were talking about, but I tried swapping it out before I got this message, I put a whole bunch of different ones in place of the 15k R222. I was still not able to get solid picture from it. I am in the process of building the svideo circuit that I showed above (not the Ben Heck one but the other one) I will let you guys know how it goes. I am hoping to get it done in the next couple of days, still waiting on some of the components.

[jacl3]

Guys I got it, 100% working. No bouncing video, color is right everything looks good!

 

I ended up building the Svideo circuit Roxburry posted on AussieArcade. He explains how to wire it into a PAL Atari Jr but I figured I would take the risk and build it and wire it into the NTSC 4 Switch Woody.

 

I built the circuit and then got one of these

 

I bent up the Luma and Sync pins ( 2 5 7 8 ) up on that socket (not on the TIA chip but on the socket) and soldered leads directly to the bent pins.

 

I did not solder to the socket with the TIA chip in it because I was paranoid about overheating the TIA.

 

For Chroma I actually soldered a lead to the board on the 2600 directly below the socket where Pin 9 is (again I had the TIA out when I soldered).

 

Originally I did the same thing with the Chroma pin on the socket that I did for the Luma and Sync pins but it did not work for whatever reason but wiring Chroma (pin 9) to the board worked.

 

I am using the channel 3 and 4 switch to switch between Svideo and Component.

 

Yes the color from Component even works on the Sharp TV (so it may be relevant to dphirschler).

 

Is it worth building the circuit? Probably. Was it easy? Not particularly. I have not soldered something that complex in years (I realize it's not that complex of a circuit but it's a lot more in depth and complex than the 2 resistor transistor mod).

 

Was this whole experience fun and extremely rewarding? You bet your ass it was.

 

Thanks again Osgeld for sending me your circuit and for your suggestions, I will definitely try that in another 2600 in the future so it won't go to waste. Thanks SignGuy81 as well for all your suggestions. I would have probably given up without the feedback.

Edited May 19, 2017 by jacl3