Atari 2600 "Heavy Sixer" - wrong colors?

[AdamAnt316]

Hello everyone. I just dug out my Atari 2600 "Heavy Sixer". Unfortunately, it seems to have issues with colors. After being turned on a few minutes, some of the colors go screwy. One example I've seen is that the greenish backgrounds of Pitfall! turn pinkish. Any idea what the cause might be, and if there's a solution? Thanks!
-Adam

[jjessop]

There is a hole in the RF casting that will give you access to a 500K pot with a small flatblade, move that around a bit to clean it up and set at the right colors. This pot sets the schmidt trigger level going into the TIA for the color burst phase (tint) of the video out.

If that does not do it (95% certain it will) the crystal ocscillator if off freq, rap it with your finger or the TIA is flaking out.

Good luck,

JJ

[AdamAnt316]

There is a hole in the RF casting that will give you access to a 500K pot with a small flatblade, move that around a bit to clean it up and set at the right colors. This pot sets the schmidt trigger level going into the TIA for the color burst phase (tint) of the video out.

If that does not do it (95% certain it will) the crystal ocscillator if off freq, rap it with your finger or the TIA is flaking out.

Good luck,

JJ

Thanks for the reply. The fact that the colors start out normal and then go wrong suggests to me that something is overheating. Could something be drifting after warmup? Another thing is, the changeover seems to be sudden, and more noticeable for some games than others. Hope this helps.
-Adam

[jjessop]

.....nothing is overheating, trust me, nothing get's warm on the main board of a 2600. You will find a heatsink on the switchboards 7805 regulator and even that's not needed.

The pot is probably dirty and jumping between values due to dust and age. Take it all apart and clean with some 99% IPA or tv tuner cleaner and it will work I bet.

JJ

[AdamAnt316]

.....nothing is overheating, trust me, nothing get's warm on the main board of a 2600. You will find a heatsink on the switchboards 7805 regulator and even that's not needed.

The pot is probably dirty and jumping between values due to dust and age. Take it all apart and clean with some 99% IPA or tv tuner cleaner and it will work I bet.

JJ

I've seen defective integrated circuits do some odd things when they come to full operating temperature. I have a CD player which runs fine for several minutes before the audio cuts out; spraying one of the ICs with freeze spray brings the audio back briefly, until the chip heats up again. I've also had a Commodore 64 which would run for about 15-20 minutes before one of the ICs (not sure which; apparently one of the ROM chips) would overheat, and the computer would freeze. That's why I figured it might be a defective IC which is causing the colors to go haywire once it "warmed up" enough. In any case, what would be the best way to access the innards of the cage area? I know these early 2600s have shielding up the wazoo, so I'm not sure what to expect when I open it up. Again, thanks!
-Adam

[jjessop]

Adam,

Before you open the casting try turning the pot a few times back and forth via the access hole in the lower left corner top side. The casting is held by 4 #2 phillip screws and pops right off. Disconnect the ribbon cable from the switch board and you can pull the PCB out, no need to remove the switchboard. The dissasembly is simply and straightforward with the more difficult part getting the plastic case snapped back in place.

There is a 16 pin 4050 CMOS Hex Buffer for the lum lines and triggers mid PCB on the right, it's VERY static sensitive so make sure your grounded.

Do not mess with the coil and it's hex ferrite slug, that's the 4.5 mhz audio oscillator adjustment.

Not to brag....I have fixed more 2600's than anybody in the world. Spent at least 3 years of my 7 at Atari fixing these PCB's on the production line to the tune of 50 per hour

Good luck,

JJ