Six Switch Problem: Color Degredation

[StanJr]

I'm playing on a sixer (not heavy) and when I flip it on, the colors are all correct. However after about 5 or 10 mins of gameplay, the colors have darkened about 3 shades. The games are still visible and playable, but the colors are wrong, darker. Flip the system off and back on, the colors are correct again, and then slowly they darken.

 

For instance, Ms. Pac-man's first maze has light pink walls and a blue field, but after several minutes on my system the walls are dark pink and the field is almost black (maybe indigo?)

 

I thought at first this was a switch box or TV issue, but I have swapped out a four switch and a heavy sixer and have no color issues at all. The problem must lie in the VCS, right?

 

So can anybody tell me what this is, and if I can fix it?

 

Thanks

 

Stan

[A.J. Franzman]

Unfortunately, this is most likely a TIA chip problem (swap it with one from another working unit to confirm). Replacing the chip will be the only fix if this is indeed the case. Be aware that it is normal for different TIA chips to display different hue (tint) values if no adjustment is made to the chroma delay (color) pot when swapping chips, but you are looking only at this specific brightness (luminance) problem -- don't adjust the pot until you've determined whether the TIA is bad. If the TIA from the problem console is bad, are you going to leave the one that you swapped in where it is, and get a replacement for the donor console; or will you put the donated chip back where it came from and get a replacement for the original problem console?

 

However, it could also be a bad component among or near the resistors which combine the 3 TIA luma outputs into a single analog signal (resistor-ladder DAC). If swapping the chips doesn't change the symptoms, it may take a lot of component testing, or a "shotgun" mass replacement to effect a fix.

[StanJr]

I *think* I am following you. It sounds like more in depth than I may be able to tinker with. Push to shove I may just give the system to someone who can fix it and get it going again, and just replace it with another system. I hate to, though, I've been playing on this system for like 6 years...