CoreGrafx output is blue - how to test/fix?

[thebigcheese]

Been busy with an RGB mod on my CoreGrafx and tonight I finally got everything looking relatively noise free. Popped it into my IFU to get it all put away and suddenly the video output is now tinted blue. Normally the text on the Everdrive menu is yellow, but out of the RGB out it is blue now (though, to be clear, I've also tested with other HuCards). Composite video still shows the proper colors. I've tested continuity on the cable and there doesn't appear to be any shorts there (though I don't have another cable to verify with). I've tested connections to and from the bypass board and done my best to verify connections on the board as well. Everything seems good, far as I can tell. I even tested from the outs of the board all the way to the SCART end of the cable and it's good. Is it possible the THS7374 went bad in all of this?

Here is a photo of the bypass board and connections: https://photos.app.goo.gl/7xcSdxEDpz1QfxVPA
And here is the underside, which is where I actually have the RGB lines connected: https://photos.app.goo.gl/JRCaMmeSTbqyd15Y6

I've resoldered every component on the board and all the wires and now I'm just stumped. I've also got a region mod in there, but that is working fine and I can't imagine that being related since composite video is working fine. I also put jumpers from input to output of the bypass board (attempting to see if any of the components are faulty) and the colors come out the same.

[NoAffinity]

You desoldered this from the HU6260, didn't you? Have you checked for shorts or cold solder there? Probably a quick reflow and check of the pins on that side of the HU6260 would be a good idea.

[thebigcheese]

You desoldered this from the HU6260, didn't you? Have you checked for shorts or cold solder there? Probably a quick reflow and check of the pins on that side of the HU6260 would be a good idea.

I did. I checked continuity from the pins themselves (rather than the pads) to the inputs of the bypass and it checked out, which suggests that there are no issues there. BUT I'm going to reflow all the pins on all chips tonight just to make sure. At some point I did accidentally pull up the pad connecting one of the analog grounds on the 6260, but I've used a jumper to connect that to another of the analog ground pins, so it should be okay. Incidentally, the black part of the chip is not conductive, right? I'm just use a resistor leg to jumper that and it definitely touches the body of the chip.

If it really comes down to it, I have a TG16 lying around that no one wants to buy because I repainted it and repaired a trace and the RGB mod is pretty ugly inside, so I can use that for parts instead if a chip is bad.

[thebigcheese]

Okay, with further testing I have come to a conclusion that makes no sense to me but I am forced to accept. I resoldered the chips and there was no change. I then actually loaded the test suite and discovered that I am getting red, green, and blue signals, but red and blue were swapped. This makes no sense because I am certain that all the connections match the right spots and furthermore, it worked with the right colors before. I have no explanation as to why the red and blue channels would have swapped, but, if I swap the wires then everything returns to normal. Very odd. Is it possible for the system to suddenly swap which color is coming out which pin?

[NoAffinity]

What monitor are you testing on? If it's a CRT, try a degauss.

[thebigcheese]

PVM and an HDTV through OSSC. Super weird. Maybe I just hooked something up wrong, I dunno. It's super weird. Anyway, working now.

[NoAffinity]

Well, I followed your pictures, without actually spending the time probing pins, and I got the exact same thing. Swapped red and blue, and it's now working perfectly, and yes, jailbars seem to be non-existent from hu card. Unfortunately, I only own one hu card, and when outputting from the SSDS3 through the internal mod, the interference is noticeably worse.

But, if you're not doing an SSDS3, this seems to be a good solution.

[thebigcheese]

Yeah, I think Voultar was saying that internal mods are pretty much crap when using an SSDS3.

Also.... oh my god, yes, I am an idiot. I can't believe how many times I looked at the expansion port pinout and still got red and blue backwards. I will have to update the guide. Anyway, I am glad to hear that aside from the SSDS3 it is a better way to route the wires! So at least I'm not a total idiot.