Basic NES Reproduction Board Guide

Please look at the main entry for more information on how to prepare the ROM file!

Here’s a quick guide on how to populate my custom designed NES reproduction PCB. This is the “Basic” version that supports NROM, CNROM, AOROM, UNROM, and UOROM games.

Front Side

PRG ROM Chip

Needed for: All game types
Part Number: EPROMs: 27C256, 27C512, 27C010, 27C020, 27C040, 27C080; Flash memory: 39SF010, 39SF020, 39SF040
Function: Holds the Program ROM file
How to Program: Check the reproduction article for information (Steps 1, 3, and 4)

CHR ROM Chip

Needed for: NROM, CNROM
Part Number: EPROMs: 27C256, 27C512, 27C010, 27C020, 27C040, 27C080; Flash memory: 39SF010, 39SF020, 39SF040
Function: Holds the Character ROM file (sprite data)
How to Program: Check the reproduction article for information (Steps 1, 3, and 4)

CHR SRAM

Needed for: AOROM, UNROM, UOROM
Part Number: 6264 series
Function: Holds the ROM’s sprite data

CIC

Needed for: All game types (unless using a top-loader NES, modded NES, or clone console)
Part Number: Original CIC, or programmed ATTiny13
Function: Completes the region check and allows the game to run on the console

C1 – Electrolytic Capacitor

Needed for: All game types
Value: ~22 uF, at least 10 V rated
Function: Smooths out supply voltage for the board due to transients on the power supply, prevents quick changes in supply voltage when power is turned off. Please note to bend it over to the right, to avoid interference with the cartridge shell.

C2, C3, C4 – Ceramic Capacitors

Needed for: All game types
Value: ~0.1 uF, at least 10 V rated
Function: 
Filters out high-frequency noise that can interrupt the EPROMs, SRAM, and CIC

C5 – Ceramic Capacitor

Needed for: UNROM, UOROM
Value: ~0.1 uF, at least 10 V rated
Function: 
Filters out high-frequency noise that can interrupt the 74HC32

C6 – Ceramic Capacitor

Needed for: CNROM, AOROM, UNROM, UOROM
Value: ~0.1 uF, at least 10 V rated
Function: 
Filters out high-frequency noise that can interrupt the 74HC161

ROM/RAM Solder Pads

Solder the middle pads to either the left or right pads for either CHR ROM or CHR RAM. If you’re using NROM or CNROM, solder in the ROM direction. AOROM, UNROM, and UOROM require bridging pads in the RAM direction.

H/V Solder Pads

This is to set the mirroring mode for your game. Solder the middle pad to either H (horizontal) or V (vertical). This will vary from game to game. If you make a game, and the graphics are all screwed up, try soldering the other set of pads – this will often fix the problem.

Back Side

Solder Pads

Solder the pairs of pads together for your indicated board type. Make sure to solder all sets of pads, and make sure only one set is soldered at a time! Example of this can be seen below for an NROM game type:

Special Cases

For 27C256, 27C512, or other 28-pin ROMs

There is a slight oversight on the board when using 28-pin ROM devices. For the PRG ROM socket, you need to bridge socket pin 30 and 31 together. A new revision of the board will fix this error. See the picture below for what this looks like.

For Select AOROM games

Some AOROM games have issues with bus conflicts. I have only found a small handful of games that exhibit this behavior – if you are unsure if that is a problem for you, contact me and I will help you out!

To get rid of this error, there is a very simple fix you can do. We need to invert the CPU_R/W line from the NES cartridge connector, and run that to the unused /OE pin on the PRG ROM. To do this, all you need is an NPN transistor (2N2222 series seems to work best), a 1 kΩ resistor, and a 10 kΩ resistor (in a pinch, you can use two 1 kΩ instead). Lift up pin 24 on the PRG ROM chip, so that it sticks out of the socket. Then, wire up the transistor as follows (RB = 10 kΩ, RC = 1 kΩ):

CPU_R/W in the diagram can be accessed by soldering to pin 9 on the 74HC161 chip. The /CPU_R/W net (the inverse of the CPU_R/W) should be connected to the lifted pin 24 on the PRG ROM. It should look something like this:

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