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Macross_VF1

Problem with flickering color

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I have a PAL Atari 2600 jr that I've just upgraded with this composite mod: https://www.console-corner.de/videomod.html. It's not the first time I've modded a 2600 with this particular mod, nor will it be the last and it has worked great so far.

However this particular 2600 have an odd quirk, when it's powered on it flicker between black and white, a distorted colour set and the correct one. If I leave it on for a few minutes the flickering gradually stops until I only get the proper set of colours. This has nothing to do with the B/W switch, nor does it have to do with the mod as it also happens when using RF. Best I can tell, it quite frankly reacts as if the colour information from pin 9 on the TIA chip isn't correctly supplied. Is it something as simple as the capacitors needing replacement or do I have a more serious problem?

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Check the output of the voltage regulator when first powering on the console. If it has been running, leave the power off for 10 minutes or so to make sure it’s cold (room temperature) before turning it back on and check the voltage immediately.  
 

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21 hours ago, DrVenkman said:

Check the output of the voltage regulator when first powering on the console. If it has been running, leave the power off for 10 minutes or so to make sure it’s cold (room temperature) before turning it back on and check the voltage immediately.  
 


The voltage regulator seems to output a steady 5V no matter if the console have been started cold or been powered on a few minutes. Even more strange is the fact that the flickering have stopped. I have done nothing else to the console, no changes, repairs or mods apart from the previously mentioned composite mod. It apparently just decided to behave itself.

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Glad the voltage regulator is good - it's a cheap part but does require desoldering the original from the board.

 

The next likely suspect is a the color potentiometer. It could have some corrosion inside it, or it could have a cold solder joint where it's connected to the PCB. If the problem recurs, I'd touch up the solder connections and then spray Deoxit into the color pot, cycle it vigorously several times and then let it dry. 

 

But in the meantime, if the system appears to be functioning normally, probably best to leave well enough alone for now. 

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I had forgotten about the color pot. Sure enough, as soon as I touched it, the colour started flickering like crazy. The solder joints didn't seem to be bad but I retouched them anyway. Also, while I don't have any electronics de-oxidizer spray at the moment, I figured I could use Isopropanol instead. Some twisting later and it seems to work as intended. 

Thanks for the help!

 

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