Repro freezing and screen garbage

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CowboyJunkie
Posts: 2
Joined: Tue Mar 26, 2024 4:24 am

Repro freezing and screen garbage

Post by CowboyJunkie »

Hi guys!

I recently got my SNESs out of storage and decided after recapping and repairing them I wanted to try making Repros,
thinking it must be cool to actually build the carts. A Flasher might be much more hassle free, but I prefer the actually "building"
of Hardware. Done quite a lot for the old Commodores (Like C64 and C16). I know how to solder and how to programm Eprom.

After my fair share of mistakes, I now have a basic hang of things.... but I have one repro which is giving me headaches:

I dumped the ROM myself from an original. The checksums and CRC are good.
LoROM, FastROM, 16MBit, US.
Burned it on a ST 27c160.
Soldered it into the Repro Board (Stanmoi)
Game starts, first level no Problem... start of second level: screen flashes, SNES freezes, fills screen with garbage.

First Guess: PPU Failure...
But NO. Burn In Test runs smoothly, no garbage, all test pass.

Second guess: the ROM. Dumped the Repro Board with my Sanni OSCR -> Everything checks out
The dumped ROM (from the Repro!!) works fine in SNES9X

Third Guess: Maybe the SNES after all???
Flashed the Dump from the Repro to my Tototek Super Flash -> works perfectly?!?!?

Fourth Guess: Maybe the Eprom?
Tried another Eprom -> same result

Fifth Guess: The CIC?
Removed the SMD Supercic from the Repro Board and soldered a 12F629 in... -> same result, crash in level 2

and of course I cleaned the Cart Connector in the SNES (was actually the first thing I did...)

I would appreciate any input! :-)

Regards,
John
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krzysiobal
Posts: 1037
Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland
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Re: Repro freezing and screen garbage

Post by krzysiobal »

1. Be sure that the ROM occupies whole memory (if it is less that the size of it, mirror it across whole memory)
2. Check if PGM/WE lines of the memories are tried to VCC
3. Check if the game requires RAM and repro-cartridge provides it.
Image My website: http://krzysiobal.com | Image My NES/FC flashcart: http://krzysiocart.com
CowboyJunkie
Posts: 2
Joined: Tue Mar 26, 2024 4:24 am

Re: Repro freezing and screen garbage

Post by CowboyJunkie »

@krzysiobal :
Thank you for the pointers.

1) The ROM was already at 16MBit (original dump). I compared the Dump to the NoIntro Database and it checks out.
2) The Rom was burned to an Eprom, I think PGM/WE is only found on Flash??!
3) The game does not require any RAM, Board ist configured for that.

Regards,
John
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