AV Famicom with peculiar graphical glitches.

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ArchieNash
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AV Famicom with peculiar graphical glitches.

Post by ArchieNash »

So about a month ago I got a grey AV Famicom because my other AV MODDED Famicom had REALLY strong jailbars. However, when trying it with my KrzysioCart, there was glitchy tile flickering on some sprites. I kinda dismissed this at the time since 1) I could still use og cartridges fine and 2) I was upgrading to an everdrive soon. However, after using the everdrive, certain games (most notably Rockman 6) had other weird graphical glitches. Is this something to do with the PPU or is it a severe case of interference (Which is what I think it is)? Thanks for any responses (I'm new here btw so let me know if I've done anything wrong).
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krzysiobal
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Re: AV Famicom with peculiar graphical glitches.

Post by krzysiobal »

1) Your console has buggy RP2C02G-0 PPU that requires 100R resistors to be soldered in series with the CPU data bus.
2) This looks like your TV has some problems with sync (?), no idea what causes that, maybe non-stable power, caused by high current consumption of the everdrive? Or maybe everdrive does something in the background with PPU SCOLL that I am not aware of.
Image My website: http://krzysiobal.com | Image My NES/FC flashcart: http://krzysiocart.com
ArchieNash
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Re: AV Famicom with peculiar graphical glitches.

Post by ArchieNash »

Definitely not anything wrong with the tv since the footage is from my capture card and it looks the same on every tv that I try
But I will check the PPU
ArchieNash
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Re: AV Famicom with peculiar graphical glitches.

Post by ArchieNash »

How would I know if the RP2C02G-0 is going wrong
and
where would I solder the resistor?
Thanks
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krzysiobal
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Re: AV Famicom with peculiar graphical glitches.

Post by krzysiobal »

I mean the console is sending some broken video signal that causes TV lose its sync, but when I played your video in slow down, it affects only the background. Energy bar, that is displayed using sprites, is not affected. Something that would happen if the PPU scroll is written in the middle of frame.

Does it have similar behaviour on other games? Is so, can you make a list of few games that have such problems and those that do not? Maybe there is something wrong with the IRQ counter (PPU A12 jitter?)

Every RP2C02G-0 has this issue. In krzysiocart, you can solder them here (don't forget to cut the track underneath them):
resistors.jpg
Image My website: http://krzysiobal.com | Image My NES/FC flashcart: http://krzysiocart.com
Fiskbit
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Re: AV Famicom with peculiar graphical glitches.

Post by Fiskbit »

#1 does indeed look like the issue fixed with in-series 100 ohm resistors on the CPU data lines. It is believed to be caused by signal reflection. The resistors must be near the cartridge, not near the PPU. It is very common for modern cartridge hardware to trigger this issue, and as a result, cartridges such as the PowerPak and Everdrive N8 Pro come with resistors in the cartridge. Except for the FDS RAM adapter, it is very uncommon for contemporary cartridges to trigger this. If possible, you should consider adding resistors within the KrzysioCart.

As krzysiobal says, this problem seems to only occur with the RP2C02G-0 PPU. However, most consoles came with such a PPU, so cartridges should ideally be designed with this in mind.

#2 looks like a problem with IRQs. The sprites are unaffected and that screen has parallax scrolling, which makes use of the cartridge IRQ to scroll differently at different parts of the screen. My best guess is that it's dirty, so make sure your cartridges and cartridge slot are clean; try using isopropyl alcohol and a qtip on the cartridge, and insert the cartridge into the slot while still wet to try to transfer dirt from the slot to the cartridge. If you're seeing this behavior specifically on a flash cart, make sure the flash cart is using the newest firmware.
ArchieNash
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Re: AV Famicom with peculiar graphical glitches.

Post by ArchieNash »

I'll probably be doing this tomorrow since it's getting late in the uk.
By the way I only have 82ohm through-hole resistors at hand. Will they do the job?
(Also opening the krzysiocart is gonna be a nightmare)
Fiskbit
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Re: AV Famicom with peculiar graphical glitches.

Post by Fiskbit »

infiniteneslives did some testing last year and said that resistors between 30 and 100 ohm fixed the issue, so value-wise, those should be fine.
ArchieNash
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Re: AV Famicom with peculiar graphical glitches.

Post by ArchieNash »

Ok tomorrow I'll (quite literally) crack this thing open)
One other thing is that, In contrast to what krzysiobal said, in every game on the cart (and even the menu) the sprites are affected (but only past tile $08 in fceux's sprite viewer). On games like Tetris this is barely noticeable since it only uses 8 sprite tiles on screen most of the time. But on most of the NES library, it's very apparent. This is why I think the life bar is very unaffected since most of it is the first 8 tiles.
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krzysiobal
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Re: AV Famicom with peculiar graphical glitches.

Post by krzysiobal »

In the summer I was lucky to borrow one of those famicoms with failty RP2C02G-0 for tests and one of the following fixed the issue:
* adding those 100R resistors (I added them there, so looks like culprit might be the 74lvc245 5->3.3V buffer

Code: Select all

                         +----------+                      +----------+ +----------+
                         |  5V SRAM |                      |3.3V FLash| |3.3V CPLD|
                         +----------+                      +----------+ +----------+
                           ||||||||            +--------+    ||||||||     ||||||||  
[cart connector]=DATA BUS==++++++++----[100R]--|74LVC245|====++++++++=====++++++++   
                                               +---------

* DISABLING CPLD's internal pullup resistors on the data bus(really no idea why pullups on the 3.3V side makes such difference).

Your version must be quite old, because starting from April, it already contains the resistors + pullups are also disabled.

You can open the cartridge using bare hands.

I discourage soldering THT resistors, you can easily lift tracks that way + they are too big and there will be issue with closing the shells.
Image My website: http://krzysiobal.com | Image My NES/FC flashcart: http://krzysiocart.com
ArchieNash
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Re: AV Famicom with peculiar graphical glitches.

Post by ArchieNash »

I've put in the resistors (albeit quite badly) and it all works! Obviously the case is not gonna go together but I'll remove some of the ridge at the bottom of the case to get it to fit.
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