Atari 2600 Light-Sixer Video Gets Dark Intermittent Sync after Warmup

[+-^CrossBow^-]

1 minute ago, Maraakate said:

Sorry, what is UAV?  Do you mean like "Ultra A/V mod" or something like that?  Because, this board is basically a rehash of the old Ben Heck mod with an extra transistor to boost output so it didn't rely on attaching itself to that.

See the schematic above I linked to. It shows you which pins off the TIA go into the 4050 and further out from there to test. And no..they won't be steady signals unless what you are viewing is totally static image and doesn't have anything moving on the screen. 

 

the UAV stands for Ultimate Atari Video and is sold through The Brewing Academy. It feeds off the signals directly from the TIA into a new video processing circuit to provide good composite and excellent s-video output from nearly all of the Atari consoles minus the Jaguar and Lynx. But I only mentioned it as I'm quite familiar with it and like the fact that it doesn't require the removal of any components off the system so you can keep the RF intact and working as a backup and to help in troubleshooting.

 

[Maraakate]

3 minutes ago, -^CrossBow^- said:

See the schematic above I linked to. It shows you which pins off the TIA go into the 4050 and further out from there to test. And no..they won't be steady signals unless what you are viewing is totally static image and doesn't have anything moving on the screen. 

 

the UAV stands for Ultimate Atari Video and is sold through The Brewing Academy. It feeds off the signals directly from the TIA into a new video processing circuit to provide good composite and excellent s-video output from nearly all of the Atari consoles minus the Jaguar and Lynx. But I only mentioned it as I'm quite familiar with it and like the fact that it doesn't require the removal of any components off the system so you can keep the RF intact and working as a backup and to help in troubleshooting.

 

By static image, yes I think this is possible with the start screen of Kaboom!.  I noticed when the problem isn't happening the output on Pin 12 is stable.

[Maraakate]

Also, sorry I think I missed part of your post earlier with the diagram.  Right now, for no real reason, the A26 is cooperating so I have the scope on the 5V going into the mod PCB.  So far it is stable, waiting to see if it changes when the screen starts acting up.

[+-^CrossBow^-]

All of the signal eventually merge to pin12 but the 4050 is in the middle of that. That is why I thought about it. Not all models of the 2600 have a 4050 in them. But the 6 switchers do and it is known to go bad in them. Console5 even mentions this I think in their notes on the refresh kits since they offer the 4050 ICs for sale.

 

[Maraakate]

I suppose you are right.  It says on Console5 that it can cause no trigger from joystick or no sync on 6 switch models.  Still waiting on the unit to act up (funny it's been acting up this entire time until now!)

[+-^CrossBow^-]

6 minutes ago, Maraakate said:

I suppose you are right.  It says on Console5 that it can cause no trigger from joystick or no sync on 6 switch models.  Still waiting on the unit to act up (funny it's been acting up this entire time until now!)

Yeah...they do that...

 

Once they know you are onto them they mysteriously start behaving properly. 

[Maraakate]

Well of course, couldn't be that easy! 😄

 

I got bored of waiting, tried taking a heat gun at progressively hotter settings on the boards and no change.  Played the game for quite some time and realized I've been playing it for over 30 minutes.  So, put it back together (minus the top) quickly and been playing for another 30 minutes.  Got 5664 in Kaboom!, a personal best (normally I peak at 3300-3500).  Maybe it's magically fixed itself or the heatgun knocked something into place or a solder blob fell off the board (already checked for solder blobs before...).  No idea, but I'll keep playing and keeping an eye on it.  If it crops up again I'll start testing around the TIA with the scope and by the 4050.

[Maraakate]

Well it appears the problem now instead manifests itself from a cold boot.  I've noticed if I leave the machine off and come back to it a couple of hours later then the problem exists for quite some time then magically fixes itself.

 

This morning I powered it up, same problems.  So I tried wiggling things around, no change.  Took out the heat gun and ran it all over the logic board and switch board.  No change, except for the colour drift which is to be expected.

 

A couple of seconds on the mod board and then it popped right into place and was perfect.  So I'm not entirely sure it could be the mod board only because the video was wonky on Pin 12.

 

And yes, +5V is good going into that board.  However, I'd have to take a peek at the schematic.  Maybe something is intermittently ground on that mod board and/or changing amount of draw from being tapped to that mod board?

 

I'll reflow solder on it just to be sure.  Only thing I can think of after this is to get a can of freon and spray the boards once the screen is GOOD and see where it immediately gets hay wire after spraying and if that doesn't find it then it's time to bust out the scope.

[Maraakate]

Small update. I took some IPA and a tooth brush and cleaned up the boards.  While I was at it I noticed the audio line that goes into the power board was touching on the metal case.  I don't think this was exactly the problem, but doesn't hurt to fix it.  So I've fixed that.  So far, so good.  The ultimate test will be bringing it over to the GFs house and hooking it up to their LCD and seeing how it holds up on first boot.

[Maraakate]

Guess it was either cleaning the PCBs or that audio line touching the metal case sometimes.  In any case, it's been a couple of days and been using it every day seems fine.