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Appee

Posted Fri Jan 13, 2023 1:10 pm

Remember how I thought there was something wrong with my 1080 monitor's composite? I am beginning to suspect it's my commodore's video output. My 40 line works only as s-video on a second monitor I own. The composite doesnt seem to work. Today I finally got an rgb cable to connect to my 1080 and the screen is red, has the letters starting mid screen and the letters are distorted. If it was just rgb I could blame the vdc, but the vic 2 or something between it and my composite output are causing issues also.

My instinct is to recap and re seat the chips and see what happens. Now I need to figure out how to identify what caps I'll need and then the best way to order them. I've never done this sort of thing before but I feel like it's about time to try.

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Appee

Posted Sat Jan 14, 2023 1:30 pm

Naturally I may have found a solution by reading. Apparently Commodore 128s produce digital rgb instead of analog which is what my Amiga 1080 was set to. So maybe just maybe adjusting that setting will make the difference. The 1080 does have a digital rgb/cga option. When I can test it, I'll let you guys know. That'll solve one of the video mysteries.

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Appee

Posted Thu Jan 19, 2023 3:15 pm

Newest update. Rgb on the Commodore is digital so that was my only issue on that front. I can't get composite video out but s video works. My suspicion is that whatever governs the composite/Luma is weak and needs chroma to act as a boost in signal. I forget think this because my jvc (which can handle both PAL and NTSC signal) can display sharp s-video but my amiga 1080 monitor is only sharp if I give up color. I wonder if recapping will solve the obvious issues.

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Appee

Posted Tue Jan 31, 2023 9:21 pm

Newest update.
I have consulted a service manual and a dedicated 128 group. The conclusion is consistent that the problem is likely a bad rf modulator as it might interfere with other outputs. I haven't cracked open the case yet, but they've emotionally prepared me for board damage. So I'm on the the right track and now I might have to solder past my skill level to bypass the modulator. Fun...

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intric8
Seattle, WA, USA

Posted Wed Feb 01, 2023 9:17 am

I took an RF modulator off a C128D a few years ago. A friend of mine had made a new version of sorts. I'd wanted access to that port hole out the back for a drive switch he'd designed, and didn't want to cut the case.

What we didn't realize was the C128 completely depended on the RF modulator - much to our astonishment. Even with his replacement we could never get it to work w/o the original in there. He'd scoured the schematics and believed he'd accounted for every single little thing.

In any case, I had to put things back together like they had been originally.

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Appee

Posted Wed Feb 01, 2023 11:53 am

So no bypassing it would seem. I've been procrastinating at looking at the potential damage. I'm really hoping it's an easy recap and maybe adding a stint to a trace so to speak.





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