NES PRG or CHR ROM Piggybacker adapters

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pausuri
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Joined: Wed Oct 02, 2019 2:24 pm

NES PRG or CHR ROM Piggybacker adapters

Post by pausuri »

Hi! I'm just starting in the NES/Famicom repros and I'd like to start translating my Jap games into English, I found a really interesting adapters in OSHPark that can be installed in the back of PGR and CHR maskrom chips:

https://oshpark.com/shared_projects/cDNEAA5d

I've tried to look for some info about this adapters but I can't find any so I decided to orders some and give them ago.

Once I've received them I burn some 29F040 but the only thing I get is a black screen when I test it.

Let me break my process down just in case I missed something:

I've used a MC3 game, SBM3.
I used FamiROM to split the ROM in CHR and PGR using the eprom size option of 512K.

Eprom burned with my GQ-4X4 using the bin format option.

With the original maskrom I tried different configurations: OE pins to VCC on both maskroms, remove the chips completely but no avail at all....

Could anyone point me in the right direction ?

Thanks!

Image Image Image
Joe
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Joined: Mon Apr 01, 2013 11:17 pm

Re: NES PRG or CHR ROM Piggybacker adapters

Post by Joe »

You've attached them to the wrong side of the board. They're supposed to replace the mask ROMs.
pausuri
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by pausuri »

The half castellated holes and the adapter name “piggybacker” adapter gave the impression that they would go in the back side of the cartridge, I’ll do some testing tomorrow, I’ll desoldering them and fit them with the right orientation

Thanks for that
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Ben Boldt
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by Ben Boldt »

Are you sure about that Joe? I agree that “piggyback” suggest you did do it the right way. Maybe you should check the pinout before powering it again.
Joe
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by Joe »

Yeah, I traced how a handful of the flash ROM pins are wired and compared it to the Nintendo mask ROM pinout. It definitely goes component-side.
FrankWDoom
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by FrankWDoom »

voultar sells a thing that matches your description. there is an installation video on the product page

https://voultar.com/index.php?route=pro ... duct_id=78
pausuri
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by pausuri »

Just a quick heads up, following Joe's advice I carefully removed everything and re solder the adapters where the original CHR and PRG maskroms were and the game finally boots up but with garbled graphics, I can play it and no issues with the sound.

I re solder all the point in the adapters and pcb just in case but same result... at least is it a step forward the right direction...

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Ben Boldt
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by Ben Boldt »

That looks like a problem with one of the lower PPU address bits (PPU A0, A1, etc). First check a different game that you didn't break your famicom/NES. Next check for bridges and opens of these A0/A1 signals. It would be a good idea to test continuity directly from the PCB edge connector to the CHR-ROM chip.

Edit:

It looks like PPU A0 is always high. This could mean it is open or shorted to 5V. Notice how all incorrect tiles are supposed to be 1 tile to the left:
ppua0_1.PNG

Edit 2:
Notice how these background color tiles are torn, it indicates that PPU A0 is open and not shorted to 5V:
ppu_a0_floating.png

There should be a connection between these 2 points (pin 25 edge connector to pin 12 am29f040 CHR-ROM):
open_circuit.png

Especially check this solder point:
check solder.png
pausuri
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by pausuri »

Hi Ben, there's continuity between 25 edge connector and pin 12 am29f040.

I'm about to start to check the edge connectors and the AM29F040 legs and check if there's any bridge or no connection at all

The Famicom works fine with other un modded games
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Ben Boldt
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by Ben Boldt »

I guess I don’t know how to explain your screenshot any other way except PPU-A0 being open… I suppose it could be a broken rom chip from when it was installed backwards but I don’t know.

Sometimes probing a bad connection physically causes contact to be made… my best advice is to retouch the soldering on all of the A0 solder joints. (Edge of new PCB and on the rom chip).
pausuri
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by pausuri »

Thanks for your advice Ben (and Joe) I found the issue! There was a bridge between the 8 and 9 leg of the eprom, after removing it, SMB3 worked with no issues!
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Ben Boldt
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by Ben Boldt »

After being confused by what you just said, I realize each tile is more than 1 byte... I am pretty sure it 2 pairs of 8 bytes (16-byte chunks) for each tile's pattern data. So A3/A4 makes more sense and A0 couldn't make sense based on your image. I am glad you were able to figure it out and nothing got broken.

https://wiki.nesdev.org/w/index.php/PPU_pattern_tables
scrofula
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by scrofula »

good evening friends. the installation of adapters provides for full contact with the plane without the use of adapter conductors. so the wifi modules are installed for example.
"Castellated pads"
Attachments
castellated-daughter-board-logitech-keyboard.jpg
scrofula
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Re: NES PRG or CHR ROM Piggybacker adapters

Post by scrofula »

I ordered myself in black, they will arrive soon
2vVDaSjB1bE.jpg
scrofula
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Joined: Sun Nov 27, 2022 10:05 am

Re: NES PRG or CHR ROM Piggybacker adapters

Post by scrofula »

2JAsIp3sbKI.jpg
I received them along with others. I will put it where possible.
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