LC575 Display Color issue - no red output (update: resolved with reflow of analog board connections)

[wottle]

Just picked up an LC 575 to use for my Mystic Color Classic upgrade. I was told it would power on but no image, so I thought maybe the analog board may be bad, which didn't concern me too much since I just want the logic board from it. However, when I got it home, I was pleasantly surprised to find that it booted just fine, including the original hard drive functioning (there were some great classic games on there). My guess is the seller didn't realize you needed hit the power button on a keyboard and was just hearing the CRT powering up when plugged in and the physical switch turned on.

There is one issue with it, and Im hoping it's not a logic board issue, but wanted to get an opinion from the group. So, the problem the computer has is that it appears as if the video signal is missing it's red component. I can see blues and greens, but no reds. It doesn't appear to be something with the RGB adjustments on the CRT, as I adjusted the levels on the back and I can make everything have a red tint.

I will probably follow @JDW 's example and try throwing it in the Color Classic to see if the problem exists there as well. If so, clearly it's an issue with the logic board. I still need to recap as well, but waiting for the caps to come in. I'll update this when I try it in the CC.

 

[wottle]

So things did not go well putting the 575 board in the Color Classic. After putting it in trying to boot, my color classic just makes a weak click with a blip of the power light. I had just started it up with the CC board and it booted fin (no HD, but got the no system disk icon). After getting into this state, I figured maybe something with the 575 board is causing problems (too much power draw, maybe) and now the CC won't boot with the original CC board. Is it possible the power supply or analog board was close to dying and the extra power for the 575 board (with the 040 processor) pushed it over the edge?

The 575 logic board still seems fine, as I put it back in the 575 and it booted fine (with no red output still).

I have a CC analog board recap kit coming, so hopefully that will fix it. In the meantime, I'd love to hear theories on what I've done to my machine.

 

[wottle]

OK, second update. I was able to get the CC to boot after leaving it powered on (switch turned on without pressing the power button on the keyboard). While I still can't get my 7.1 disk with the System enabler on my BlueSCSI to be recognized, I can get it to show the "Welcome to Mac" screen using a stock 7.5 disk from my RaSCSI before it crashes. And on that screen, I see that the red output is fine. So it seems my 575 logic board is fine as far as showing all colors.

Now I just need to figure out why it won't boot off the 7.1 HDA I created for it. More to come.

 

[wottle]

Just realized I never posted my update. The booting issue was a user error on my part. I hadn't formatted the SD card properly. My CC works great with 7.1. Up next will be a recap of the analog and logic boards, and hopefully updating it to 640x480 once the analog board is cleaned up.


As for the lack of red output, on a Youtube live session a while back, @Branchus recommended checking the analog board connector, so I'm hoping to crack open the 575 to inspect the solder joints on the analog board. I'll post with whether I found anything and if a reflow or re-solder resolves the issue.

 

[wottle]

In case anyone runs into a similar issue, I was able to resolve it using Branchus' suggestion of looking at the analog board connectors. I reflowed all of the connectors between the CRT and the analog board (paying particular attention to the red connections. When I reassembled after reflowing / adding a bit more solder, the red colors were back the the display looks great.