Sega Neptune - Building a Sega Neptune

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The PCB can be ordered prepopulated from JLCPCB or PCBWay

DVIZIX's 3D shell is private.
https://www.pcbway.com/project/shareproject/PROJECT_NEPTUNE_8295fd26.html

I only know of one other shell that was in dev. on twitter and haven't heard from that person in a long time.
I would like a shot at printing one as well.
That explains why I can't find the stl. It doesn't exist. Guess I'll use the Genesis Model 2 shell. I did order the board from JLCPCB but without components. Not sure what I'd be missing without it being populated?
 
That explains why I can't find the stl. It doesn't exist. Guess I'll use the Genesis Model 2 shell. I did order the board from JLCPCB but without components. Not sure what I'd be missing without it being populated?
Pre-populated with the most common components.
Saves time and in some cases, money.

Of coarse, the model 2 shell will work just fine.
Its proof to me tho that the Neptune shell itself has far more appeal than what's really inside it.
At this time it is, and I could be wrong, the second most expensive way to play Sonic the Hedgehog.
But there all some cool new games for the 30 year old system.
(including one killer re-worked app called DOOM)
 
Last edited by MicroNut99,
Pre-populated with the most common components.
Saves time and in some cases, money.

Of coarse, the model 2 shell will work just fine.
Its proof to me tho that the Neptune shell itself has far more appeal than what's really inside it.
At this time it is, and I could be wrong, the second most expensive way to play Sonic the Hedgehog.
But there all some cool new games for the 30 year old system.
(including one killer re-worked app called DOOM)
That's why I wanted to do it. For the awesome looking shell. Doom Resurrection is also pretty cool. I'm also hoping to put in an HDMI connector as well. Haven't really looked into it.
 
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That's why I wanted to do it. For the awesome looking shell. Doom Resurrection is also pretty cool. I'm also hoping to put in an HDMI connector as well. Haven't really looked into it.
A stripped down RetroTINK x2 Scart to HDMI will fit.
There maybe other upscalers that also work.
But I dont know about quality.
If you find something cool then let me know.
Thanks!
 
I got the boards as in 5 of them. No components, which I may regret. They have a nice interactive diagram that shows which components go where. I wonder if I can get most of this off the Sega Model 2 board? Found a photo of what it should look like. Like, 48X 100nf capacitors? At least they're 0805 which makes them easy to install. Only $9 off Amazon for 200x of them. I have capacitors but not 48x of them. Considering how many plastic like components are near things I'm going to hot air parts on, I'm better off putting in the chips and SMD components before electrolytic caps and the cartridge slot. Here's a crappy Model 2 diagram if I wanna switch parts to the Neptune board. Which I probably will.
NepuneC4U.jpg
UkJpYBfcky11Xovp.huge

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Soldering the two main Sega Genesis was pretty easy, but the SRAM chip drove me nuts. The problem was where it goes, because instructions aren't clear. I figure it goes where the board labels LHP6323 since everything is belongs to something else. I tried going by videos and photos of what other people did, and they put in a SANYO LC331632M-12, which is also a 512K-bit SRAM chip. Anyone can confirm that's where the Toshiba chip goes? I'll continue this tomorrow.
PXL_20260227_054330082.jpg

PXL_20260227_054343897.jpg
 
Last edited by Dukenukemx,
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Soldering the two main Sega Genesis was pretty easy, but the SRAM chip drove me nuts. The problem was where it goes, because instructions aren't clear. I figure it goes where the board labels LHP6323 since everything is belongs to something else. I tried going by videos and photos of what other people did, and they put in a SANYO LC331632M-12, which is also a 512K-bit SRAM chip. Anyone can confirm that's where the Toshiba chip goes? I'll continue this tomorrow.
The pinouts and even description between the SANYO LC331632M-12 and Toshiba TC511632FL chips look the same to me, so it's pretty safe to say that it's where the IC goes.

https://www.alldatasheet.com/datasheet-pdf/view/40652/SANYO/LC331632M-12.html

https://www.alldatasheet.com/datasheet-pdf/view/1460318/TOSHIBA/TC511632FL.html

The only other place where it'd fit is IC7, but that's for the DRAM.
https://www.alldatasheet.com/datasheet-pdf/view/134839/OKI/MSM54C864.html
 
Got the easy part done. All the major chips are on the Neptune board. I'm at the hard part where I need to source all the surface mount devices that need to be placed on the board. Before I go hunting on Digikey and AliExpress for parts, is there anything else I can salvage from the Genesis and 32X? Besides controller and cartridge ports. I'm definitely going to try and source as many components as I can from them, besides electrolytic capacitors. I don't trust the brand caps Sega put in these consoles.
PXL_20260303_000631092.jpg

PXL_20260303_000642359.jpg

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Did some looking around and I think I need these components for sure. I need help confirming if these are the parts I need. I have a booklet of SMD caps and resistors from my many attempts at fixing Nintendo Switch's.

I need 8x Resistor Networks & Arrays 10K OHM 5% size 0603.
EXB-V8V103GV
https://mou.sr/4smahHw

1x TL972IPWR Operational Amplifiers
https://mou.sr/4aMKW3B

1x THS7374IPW Video Amplifiers 4-Ch
https://mou.sr/4cXbyQA

1x LQH55DN471M03L Coil RF Inductor.
https://mou.sr/4u5HCYP

1x CAT16A-222J4LF Resistor Networks & Arrays 2.2K OHM 5% size 0603
https://mou.sr/4rN2Fh5

4x Capacitor Arrays & Networks 33PF 50V 10% size 0603
https://mou.sr/3Nc8WnC

2x Resistor Networks & Arrays 4.7K 5% CONCAV SQUARE 4X0603
https://mou.sr/4aNN2QI

1x Switching Voltage Regulators 3-V to 17-V input vo ltage 4-A FCCM mode
https://mou.sr/40C82ns

1x Feedthrough Capacitor 2200 PF
https://mou.sr/4b3BZS8

3x Bipolar Transistors - BJT NPN GENERAL PURPOSE
https://www.mouser.com/ProductDetail/onsemi/MMBT3904LT1G?qs=HVbQlW5zcXUYZ2Fy0YF3FQ==

1x Buffers & Line Drivers Tri-State Octal A 59 5-SN74ACT241PW A 59 A 595-SN74ACT241PW
https://mou.sr/4cY7tf4


Just updating the parts list. I don't want to order again and pay for shipping twice. I did find four 10k resistor arrays on the 32X board and they seem to fit just fine. I thought I found six but the two I found near the cartridge slot are large and have more connections. I also found three NPN SOT-23-3 transistors labeled L5, which I think may work just fine in the Neptune board? Would like help with this one because I'm no electronics expert. I can melt stuff off a circuit board and melt stuff on, and that's it.
PXL_20260303_163254322.jpg

PXL_20260303_163709285.jpg
 
Last edited by Dukenukemx,
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I need help identifying a part I need. D801 says I need a 2A RECT D_SOD-128. I'm assuming it needs to be a 2 amp rectifier size SOD-128, but is it a diode rectifier and if so which way does it get installed?
 
Is there a board viewer for the Cosam neptune board? I'm not getting 5V or 3.3V and I can't figure out why? The buck converter is putting out 1v or 0.8V depending on where I test it.
 
I completed the board and it doesn't output anything. TV doesn't even pick up a signal. There are components I missed because I have no idea what if any I put there. They are marked with an asterisk. Anyone have a clue what goes there?
PXL_20260504_033716405.jpg

unknown components neptune cosam.png


**EDIT**
A person that goes by the name RGBeter from Reddit has given me the info. This board isn't as well documented as it should be. Here's what is needed for anyone doing this. Also, this section deals with composite video output, which explain why I see nothing when I turn on the board.
955es3rgq1zg1.jpeg
 
Last edited by Dukenukemx,

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