GBDSO

GBDSO

GBDSO Website : http://swelectronics.co.uk/Gameboy/DsoDemo/DsoDemo.htm
GBDSO Elektor article : http://www.radanpro.com/Radan2400/TestShematics/GameBoyScope.pdf
GBDSO BOM list (2019/02) : https://docs.google.com/spreadsheets/d/1vu9Xc1Mw5STfz_mAsAOrmmyRrHJMRS4_JKM7iif-KBE/edit#gid=0

Max Voltage Ratings

• +/- 16V on 1:1
• +/- 50V on 10:1

Do NOT exceed the max voltage ratings or you risk damaging the cartridge and the Game Boy.
I'm not responsible if it blows up!

Schematic

PCB

Game Boy test

Since the big v2 update on 2021/01/08, this GBDSO board works on both channels.
See pictures below:

Official game cart dimensions

Below you'll find the dimensions for the PCB of an official game (Pokémon Yellow JAP).

Programming the AT27C256R

The first jumper JP1 selects either 5V to pin 2 of the PROM (VPP) and VPP from the unused 5th edge connector.

The second jumper JP2 cuts the power going to the rest of the board.
While in programming mode, the PROM needs 6.5V to VCC and I'd rather not have it power to the rest of the board.

To program the PROM, leave JP2 open and set JP1 so that the edge connector VPP is connected to the PROM VPP.
When programming is done, bridge JP2 and set JP1 so that 5V go to the PROM VPP.

GBDSO PROM to PDIP28

Any decent Universal Programmer should be able to program the PROM on the cart.
You can see the adapter board on the 3D rendered board above.

The Game Boy connector uses the Xunbeifang GNI172 footprint made by obskyr from the gbdev discord.
You can find other Game Boy connectors made by Gekkio here: gekkio-kicad-libs.

The Xunbeifang GNI172 can be found on aliexpress.

To program the PROM, leave JP1 open and close JP2 as shown below.

Plug the adapter board into a Universal Programmer and set the target device to DIP28 AT27C256R.

Note: This part of the board has not been tested yet, so I hope it works.

Original GBDSO

Original GBDSO pictures from November 2000 courtesy of Tauwasser on the gbdev discord.

BOM list

Total Price: 31.31€
Total Components: 70

Replacement parts

The input opamps MC33182D is not being sold anymore, at least not on digikey.
So looking around I thought the TL062 would be a nice replacement but the numbers weren't quite similar.
I've looked at the TL072 and this one looks pretty good, the only downside is that it isn't a low power opamp.

If we compare the current consumption from the TL072 and the MC33182D, the TL072 uses 5 times more current (1.4mA typ.) than the MC33182D (420µA).

Looking further into the MC33182D I found this old forum post talking about replacing it on a GBDSO : edaboard forum
They talked about the TL082, LF412, TLE2082A and TLE2602. Someone used that last one as a replacement for the MC33182D, although digikey has it priced at around 2$ per unit...

Looking at the information page on TI's website, this is what they say:

The TL206x devices are pin-compatible with other TI BiFETs; they can be used to double the bandwidth of TL06x and TL03x circuits, or to reduce power consumption of TL05x, TL07x, and TL08x circuits by nearly 90%.

That power reduction is crucial for long lasting batteries.
For now though, I'll try the TL062 I currently have and will try the TL072 on a later date.
I'll also try to find a suitable, pin-compatible, low power replacement opamp for the TL072.