Author Topic: Fixing bad CV1000 Graphics NAND blocks without any soldering  (Read 154 times)

Offline buffi

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Fixing bad CV1000 Graphics NAND blocks without any soldering
« on: October 26, 2021, 03:21:28 AM »
Thought I'd just make a small cross-post of this here, since it should be relevant for people who are not on Arcade Projects forum.

A while ago there was a Espgaluda 2 sold on YAJ that had sprite issues when bombing. https://page.auctions.yahoo.co.jp/jp/auction/x1005199728
The dude buying it sent it to me to let me have a look at it, and I managed to fix the issue by remapping the relevant sprites to clean blocks on the NAND, that had some data that had gone bad. PCB has since been returned to new owner which seems happy with it.

To quote mame source code:
"Cave often programmed the u2 roms onto defective flash chips, programming around the bad blocks.
As a result these are highly susceptible to failure, blocks around the known bad blocks appear to
decay at an alarming rate in some cases, and in others data has clearly been programmed over
blocks that were already going bad"


When this happens, one option is to just burn a new one and swap it, but now that CV1000 JTAG is fully documented (by me here: https://github.com/buffis/cv1k_research/tree/main/JTAG), this is very fixable without any soldering.

There's a full writeup on the procedure I did to fix the PCB here:
https://www.arcade-projects.com/threads/espgaluda-2-cv1000-repair-of-bad-u2-nand-using-jtag.19108/

There's quite a few steps, but it should be very possible to do the same procedure for other PCBs with similar issues. Don't attempt unless you know what you are doing though.

Offline emphatic

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Re: Fixing bad CV1000 Graphics NAND blocks without any soldering
« Reply #1 on: October 27, 2021, 03:19:15 PM »
Wow, that's very awesome. Does this mean that bad sound can be fixed as well in games such as SDOJ?

Offline buffi

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Re: Fixing bad CV1000 Graphics NAND blocks without any soldering
« Reply #2 on: October 27, 2021, 05:55:58 PM »
Nope. Sound roms are completely unrelated unfortunately.