Another VCS with no colour after composite mod

[Another VCS with no colour after composite mod]

1. 2.47V DC / 0.138V AC

 

2. I'd rather not mess with that cable right now but it's an interesting thought

 

3. Sadly no oscilloscope here, only a logic probe

 

Thanks!

[Another VCS with no colour after composite mod]

 
Ya know, there is one other possibility.  I think it had been suggested to try on a different TV back when you were having the color problems.  Now that the color problems are solved, does the non-digital TV look any better?  I'm curious because that weird blocking looks similar to MPEG-based issues.  Perhaps the TV is creating its own problems, then trying to filter them out?
 

I have tried 3 TVs...

[Another VCS with no colour after composite mod]

BTW - watched your first video on this project today. I enjoyed it quite a bit, but whatever dark magic you used to make yourself and Lady Fractic look like 10 year old kids freaked out my eyeballs.  

Haha glad you liked it. That was a Snapchat filter I found, along with some bluescreen fun.

[Another VCS with no colour after composite mod]

Thanks. This has been my suspicion as well based on advice from Luke/Console5, so I have a new PSU en route from him as we type. 🤞

[Another VCS with no colour after composite mod]

Here are the AC readings at various +5V DC points:

• Voltage regulator: 0.005V AC
• TIA: 0.005V AC
• RIOT: 0.001V AC
• CPU: 0.004V AC
• Inductor: 0.005V AC

What does this tell us and how can I use it to help the noise? Any other places to try? Thanks!

[Another VCS with no colour after composite mod]

Sorry didn't notice you said AC mode.

 

What does that test for specifically related to the picture noise? AC interference?

 

 

[Another VCS with no colour after composite mod]

That blue Matrix streaking shouldn't be happening.
 
If you put the meter in AC mode and measure the +5V at various points, what do you read?

Solid 5V at the regulator and pins of each chip. Any other points specifically to test?

[Another VCS with no colour after composite mod]

After replacing the ribbon cable that connects the switch unit on this heavy sixer with a new Dupont assembly, for some reason the picture quality improved fairly significantly. My only question now is whether I should be expecting better composite video quality on a 1977 revision 2 heavy sixer than this?: https://photos.app.goo.gl/7MU1NqU7JqrEuEW46

[flat ribbon cable]

Before and after:

 

Picture quality improved significantly!

 

[Another VCS with no colour after composite mod]

Ok thanks. I don't think the Jack is the issue, but I'll try that as a last resort. I'm just waiting a new PSU which is currently the #1 suspect.

[Another VCS with no colour after composite mod]

A.S.A.P. man... 
 
Another suggestion I was going to toss out was to wire in an actual RCA jack temporarily off the composite output and tie it to ground along the mainboad somewhere to see if that would rule out the AV jack currently being used.
 

Right. Where would I wire it to? Directly to the Atari main board? I thought there were resistors required in between?

[Another VCS with no colour after composite mod]

Well, you could see if there is continuity between the outer conductor of the video plug at the TV and a ground point on the Atari.

Yup there is.

Luke at Console5 suspects it's my after market DC transformer. Makes sense. I'll try a better one.

[Another VCS with no colour after composite mod]

I'm no expert but have you tried a different TV?
 
I had one TV that no matter what modded system I used I got similar symptoms (color for a second then gone, garbage on screen, etc...) I tried a different flat screen and it was fine...
 
 
Just throwing it out there....

Thanks yes I tried that. Same on both the widescreen LCD and a Sony BVM.

[Another VCS with no colour after composite mod]

Possibly.  You should try to pinpoint the most effective location for affecting the picture quality.  If it's the AV plug itself, (looks like it's a stereo headphone jack?), then it could be that you have a bad connection in the jack itself.  Or it could be, for instance, that the AV cable has a defect where the ground wire doesn't quite make contact with the plug.  Something like that.

Ah sadly I tried all that and there's just no rhyme or reason. Anything and everything can affect it. It could just be that a SMD board isn't the way to go and is prone to interference. I am going to swap the ribbon cable that connects to the switch board, though I doubt that's the cause.

[Another VCS with no colour after composite mod]

13 minutes ago, ChildOfCv said:

Is the interference affected by moving the AV cable or playing with the plug?

Yes very much so. Also touching the voltage regulator sometimes does it, or moving the PCB up and down separate from the top 6-switch board (when I have them out of the case).

 

I've tried changing the composite wire to a better one but no difference.

 

Sounds like you might have an idea what's going on though...?

[flat ribbon cable]

Please disregard. I just realized I can use headers and Dupont cable. I hadn't expected that the spacing standard would still be the same but it is.

[flat ribbon cable]

Bumping this question. Anyone know of a replacement wire with sockets? Thanks.

[Another VCS with no colour after composite mod]

14 minutes ago, -^CrossBow^- said:

The really odd artifacts in that video go away as soon as they start the game. So the graphic rolling bars etc are showing up when the game screen is doing the color cycling in DK as I believe it does when you plug it in, turn it on and just leave for a second or so. 

Right that's what I've seen. So is that "normal"? The actual gameplay isn't terrible. But also not great. There is a band of interference moving up screen and general noise. Another video. Watch towards the end: https://photos.app.goo.gl/xuNeHM2NuXTggXsu5

[Another VCS with no colour after composite mod]

2 hours ago, ChildOfCv said:

Hmmm.  Ground point looks like it should work.  But that is some weird interference, almost looks like something else is trying to butt in.

 

Maybe you could post a picture of the whole PCB in its current condition, to see if anything looks off.

I appreciate that. Here's hi-res pics.

[Voltage Regulator pads lifted up - repair OK?]

What was the issue?

It was something to do with this ¯\_(ツ)_/¯ https://r.tapatalk.com/shareLink/topic?url=https://atariage.com/forums/topic/311859-another-vcs-with-no-colour-after-composite-mod/&share_tid=311859&share_fid=4675&share_type=t&link_source=app

[Voltage Regulator pads lifted up - repair OK?]

Update: I fixed the issue I was having and the VR repair above seems to have worked and was not the cause. 👍

[Another VCS with no colour after composite mod]

55 minutes ago, ChildOfCv said:

Well, I went by the Atari VCS Service Manual.  It has 2 revisions and schematics for the 2600A, and one for the 2600 sixer.

 

 

Your picture shows R215, but in the service manual that's R213.  That seems to be a misprint, because there's also a R213 near the TIA, in the same drawing. And I can't find a R215 anywhere else on the drawing.

 

R216 is where sound mixes into the composite video.  I'm not sure why they didn't have you remove that one, but I have a suspicion that that's the one you should have removed instead.  That does seem to fit the theory of Tynemouth's instructions, at least.  Then the yellow wire connects to the side of R216 that faces the composite video resistor ladder (should "beep" on one side of R215 and R222-R224 and R234).

 

http://www.robotsandcomputers.com/computers/manuals/atari2600_fsm.pdf

 

What can I say. You're a genius! It works!

 

I believe the issue was Tynemouth thought it was more complex than it actually was, telling me the part numbers would be different for my heavy sixer to the ones in their instructions for the light sixer. Whereas in reality they are the same part nos. So I was advised to remove R215 when actually the way I did it before that by removing R216, was correct. But to be fair this was probably my fault as I had another red herring at that time with a faulty TIA chip which is why we were trying other things.

 

Long story short, the only resistors that needed removing were R209 and R216. Here's how the board is patched now. Yellow goes to the bottom of R216 as the top pad gave up on life:

 

Moving on, the picture quality isn't great. Is there anything I can do to fix the various issues exhibited in this video? Other issues include some vertical roll at times. Would the place I've patched to ground cause this or is that unlikely?

 

Thanks for all your help and for getting me close to finished with this project!

[Another VCS with no colour after composite mod]

R215 is supposed to patch the color output into the composite signal.  So, make sure you didn't eliminate any of those from the board.

Thanks, I'll check the other things, but per my photo I did remove R215. Are you sure that's the same on the heavy sixer as what you're referring to? I was directed to remove it by another person.

If I reinstate R215, then looking at my circuit, where should the yellow wire patch into?

Thanks!

[Another VCS with no colour after composite mod]

3 minutes ago, x=usr(1536) said:

Dumb question: does this happen immediately after switching on the 2600, or does it happen after a period of time?

 

The way that things are happening intermittently makes me wonder if it's not a heat issue.  Any components getting uncomfortably warm?

 

Oh, and voltages - those still looking good?

 

Also, what happens if you revert the mod back to stock?  I know it would suck to have to do that, but could potentially show up which side of the equation the problem is sitting on.

 

Basic questions, I know (and I'm aware of your background, so know that you know that ), but figure it's worth mentioning regardless.

Not a dumb question at all. The issue is apparent immediately upon power up. Sometimes I get colour for 1 second then it goes to B&W. So the system is cold (not a heat issue I'm pretty sure).

 

I get 5V to all 3 chips and the composite wire. Not sure where else to check specifically but feel free to let me know.

 

I'm probably not able to revert the mod due to my sanity!

 

Thanks!

[Voltage Regulator pads lifted up - repair OK?]

Hi guys, unfortunately whilst replacing the voltage regulator in a Rev B Heavy Sixer, the 3 pads lifted off the board. Normally I'm super careful, and this isn't an excuse (I do feel bad), but there seems to be an issue with the locking pin/anchor of the heat sink on the VR. At the factory, before I touched it, it looked like they'd tried to solder the anchor to the ground trace, but the solder never took and wasn't holding the anchor at all. The anchor was loose from the board.

This meant all the strain was on the VR pins and their pads. I'm guessing that because the heat sink was dispersing the heat so fast, they couldn't successfully solder to it.

 

Anyway, I went ahead and repaired as follows using house electrical wire for 2 reasons:

1. To take the traces to their next pads
2. To add support so these 3 wires now act as sturdy legs

 

It is much stronger now, and I get solid continuity from the VR pins to their destinations. However I am having picture quality issues (keeping these threads separate in case it's a red herring), and wonder if the repair as I have carried it out, is acceptable? Can you see any reason this repair would cause issues if the continuity is good?

 

(The anchor remains unsoldered to ground because it just won't take any solder. Does it have to be grounded? Surely that wouldn't affect the picture.)