AES Color Problem

Been working on this one for a while now. I've got a 3-5 AES that has had a color problem that I can't seem to fix.

It actually looks pretty close to okay, but white and shades of white appear light blue. It shows a palette ram error on the diagnostic.

So far I've recapped it, replaced the palette ram chips, replaced the palette multiplexer chips, reflowed every solder joint in that area, checked continuity and impedance on every resistor, and did the RGB mod. After all of that I'm pretty much stumped. Couldn't find any similar issues in searching, either.

Are the color bars even? I’d say check the DAC.

The color bars look pretty bad. I'm also now noticing the top of the screen has a red gradient to it as well.

I replaced both video DAC chips with new ones as well.

I never pulled up the color bars but I had what seemed like the exact same problem recently on an AES 3-5. Turns out in my case that it was caused by conductive RA flux residues after socketing the RAM and BIOS. I don’t normally clean it until after I finish the work/troubleshooting, but this time it was seemingly causing the trouble. Cleaned it with 99.9% iso and the problem went away... instantly and seemingly forever.

I was using this stuff:
https://www.sra-solder.com/mg-chemicals-4896-227g-sn60-pb40-x-040-no-clean-leaded-solder-1-2-lb

They actually misidentify it as “no clean” in the product name/description!

Not the DAC chips, the actual video DAC which is a bunch of resistors. Check the set for Red itself.

CZroe said:

I never pulled up the color bars but I had what seemed like the exact same problem recently on an AES 3-5. Turns out in my case that it was caused by conductive RA flux residues after socketing the RAM and BIOS. I don’t normally clean it until after I finish the work/troubleshooting, but this time it was seemingly causing the trouble. Cleaned it with 99.9% iso and the problem went away... instantly and seemingly forever.

I was using this stuff:
https://www.sra-solder.com/mg-chemicals-4896-227g-sn60-pb40-x-040-no-clean-leaded-solder-1-2-lb

They actually misidentify it as “no clean” in the product name/description!

Click to expand...

Gave it a good scrub and it didn't seem to help. Reflowed all of the resistors in the DAC array, also didn't help.

Dr. Meat said:

Gave it a good scrub and it didn't seem to help. Reflowed all of the resistors in the DAC array, also didn't help.

Click to expand...

Not reflow, check the values. Make sure they didn’t go bad.

Just to make sure, they are the ones in the top left corner of the board.