Voultar wrote:Pin 154 of the ASIC is the "compensation pin", it's supplied with a (C11) 47nF couple cap that goes into +5V.
Now keep in mind, C11 is a 47nF that's 20%. It could be 37.6nF up to 56nF. Depending on the age/performance of this capacitor, it can be inadequate to slow the response down. If the response rate is too fast you're going to generate too much current. This feedback node is going to realize it's generating too much current, too late. This is when you get the "wobblez" at the beginning of the stage until the feedback network finally lines it out. Much like Gigaboots' captures, you can clearly see this occurring.
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1) No, this phenomenon isn't a problem with the 1CHIP ASIC itself, or its design. It's simply a matter of an aged component that may have lost performance or was slightly undersized by Nintendo. Cheap bastards..
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3) Is this a wide-spread issue? Not in my experience. I've sampled several 1CHIP systems when designing my own little doodads for the thing. I know RetroRGB has done extensive testing as well. It's certainly out there and systems can be affected, but I don't believe it's impacting more systems than it isn't.
I'm fascinated by why consoles with the stock C11 capacitor can have such a different degree of the ghosting problem. I have a 1CHIP-02 which displays the problem prominently, while my Mini doesn't visibly have it at all.
In the theory that it's caused by an aged or poorly-performing 47nF cap (and my reluctance to introduce the top black bar glitch), I thought it would be interesting to just try replacing C11 on my 1CHIP with an equivalent brand new 47nF cap with a stricter +/- 5% tolerance.
To my disappointment, the result is little or no change in the ghosting.
Ruprit wrote:Posting to confirm that Voultar’s recommendation has successfully removed the vertical banding and ghosting on my Super Nintendo Jr. Before Voultar found the source of the problem, I recapped the system and it made the banding and ghosting much more prominent. Glad to have everything fixed and I dare say the colors look even better than before the fix. Though that’s probably a placebo.
Ruprit's experience is interesting, no? I can add my anecdotal example that both my 1CHIP and Mini have been fully recapped, but again only the 1CHIP displays the ghosting. (I can't remember whether the 1CHIP had any ghosting before I recapped it. I only tested it briefly in stock condition before starting to mod it.)
But it does make me wonder if the other additions to my 1CHIP have anything to do with amplifying the ghosting (78S05 vertical line fix, 10uF IC-decoupling caps for jailbar fix, dejitter).