Yellow tint after caps replacement

[televizora]

Today I replaced the caps of old pcb with pentium4. Now the internal video outputs yellow, where should be white. I had a hard time replacing the caps, it was extremely difficult to unsolder them. I have had no issues with other boards, but this particular was pain in the... I damaged something or what? The PC otherwise works just fine. Its not the VGA cable. Usually it's much easier to replace the caps on mobo. Have experience with other mobos. Even crancked on max temp I was barely able to unsolder the caps. I wasted more than hour on 7 caps. The solder just refused to melt.

[Topcat]

Re: Yellow tint after caps replacement

My guess is you probably created a solder bridge and shorted something or inadvertently knocked a component loose. I'd check it over very closely, even use a magnifier if possible....it could be something VERY tiny. THis has happened to me before...not the 'yellow' symptom, but other symptoms it created. Some of the horrid RoHS solder during the RoHS transition years was extremely difficult to work with.

[televizora]

Re: Yellow tint after caps replacement

My guess is you probably created a solder bridge and shorted something or inadvertently knocked a component loose. I'd check it over very closely, even use a magnifier if possible....it could be something VERY tiny. THis has happened to me before...not the 'yellow' symptom, but other symptoms it created. Some of the horrid RoHS solder during the RoHS transition years was extremely difficult to work with.

I replaced 1 cap near the chipset, that is also the integrated video. Even with 50W soldering iron, crancked on MAX temperature(I almost never go to the max, even when reworking motherboards) it was very difficult to unsolder, even considering the fact that I tried to apply a low temp solder and melt the joint that way. The tip just sticks to the joint, but I cant unsolder the cap. The thermal compound under the chipset was just a thin layer of yellowish residue.
I looked at the mobo, but saw no apparent solder bridges or shorts. It took me more than hour of cursing to remove and replace just 7 caps.
Otherwise this is still somewhat capable Pentium IV 3Ghz 3GB DDR2 computer system.

[Topcat]

Re: Yellow tint after caps replacement

I replaced 1 cap near the chipset, that is also the integrated video. Even with 50W soldering iron, crancked on MAX temperature(I almost never go to the max, even when reworking motherboards) it was very difficult to unsolder, even considering the fact that I tried to apply a low temp solder and melt the joint that way. The tip just sticks to the joint, but I cant unsolder the cap. The thermal compound under the chipset was just a thin layer of yellowish residue.
I looked at the mobo, but saw no apparent solder bridges or shorts. It took me more than hour of cursing to remove and replace just 7 caps.
Otherwise this is still somewhat capable Pentium IV 3Ghz 3GB DDR2 computer system.

Maybe something got fudged up between the layers of the board. What happens if you add an external GPU (AGP or PCIe, not sure which it is)?

[televizora]

Re: Yellow tint after caps replacement

What happens if you add an external GPU (AGP or PCIe, not sure which it is)?

Everything is just fine with external GPU. And Windows7 otherwise works just fine. The problem is not due incompetence, it was just waay to difficult to remove and replace the caps. It's a PCIE board with DDR2 RAM. After I spent an hour with this board, I thought that It will not boot ever again. It booted and works, but with yellow tint on the internal video. With PCIE video card everything is ok.

[Topcat]

Re: Yellow tint after caps replacement

You've lost your blue drive on your onboard GPU, which is a classic solder bridge, trace damage, or component knocked off. To create a white raster, it takes an equal drive of red, green, and blue. If you remove the blue, what's supposed to be white will be yellow.

[televizora]

Re: Yellow tint after caps replacement

To create a white raster, it takes an equal drive of red, green, and blue. If you remove the blue, what's supposed to be white will be yellow.

Yep, I know this. But I was no near the integrated GPU itself, but near the power supply of the chipset/IGP/. If it was a power supply failure, I think that much more would be wrong, than a yellow tint. I will recheck the board.

[televizora]

Re: Yellow tint after caps replacement

I found no solder bridges, all caps are soldered with right polarity, every joint seems ok. I lost more time than I can spend on this machine, so I just put a dedicated video card on the PCI-E slot and closed the case.

[momaka]

Re: Yellow tint after caps replacement

You've lost your blue drive on your onboard GPU, which is a classic solder bridge, trace damage, or component knocked off. To create a white raster, it takes an equal drive of red, green, and blue. If you remove the blue, what's supposed to be white will be yellow.

^This.

Follow RGB lines from VGA connector back to Northbridge. Somewhere on the way, they should be going through ferrite beads and may also have a few low-value ceramic bypass caps to ground. Check that ferrite beads are not broken off or damage and also check that ceramic caps are not shorted to ground.

I've had to do this kind of repair on many discreet GPUs that I got from eBay. Usually the cause is improper handling, but could also be a faulty solder joint from the factory that just appeared now as you flexed the board around while working on it. If this is not the case, also check the RGB pins in the VGA connector. Sometimes, they can become pushed in and short on the back of the connector.