Hey guys
I’m no electronic engineer or hardware expert but I noticed this is the forum to go to when you want to talk some ! There’s some super well educated people on here who really know their stuff.
I made a new master system mainboard- but I’ve lost the enthusiasm I initially had.
The schematics are AN ABSOLUTE MESS- The boards “ok”
It loads the bios. Outputs correct audio when I botched in a 1.5k pull-up into the audio circuit .. I flashed a Japanese (2.1?) bios onto an MC27C256B and that loads. Alex Kidd loads and responds to controller inputs. The front silk says 3k3 but I used 330ohm as per French schematic it’s based off.
Everything looks ok on my little pocket O-scope
But the graphics are garbled.
It won’t boot carts
Likely issues: (most likely to least)
the way I re-interfaced the vram with the VDP.
The ram being SRAM as opposed to XRAM with pin one being NC floating. I figured there must be a reason they always use NEC xram as VRAM but not always as system ram.
My VDP didn’t quite survive the transplant
Anyway , the schematics an absolute mess , and I’m quite embarrassed and ashamed of this.. but the fun parts laying out the PCB so forgive me
What I’m getting at, is I’ve released the kicad files publicly on sms power for anyone wanting to complete this project.
Cheers
SMSII Mainboard prototype public release
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VajSkids Consoles
- Posts: 123
- Joined: Tue Jul 07, 2020 10:22 am
Re: SMSII Mainboard prototype public release
What was the motivation for making a new board?
Drop in replacement with new features with some parts transplanted from an original SMS, or a from ground up new machine with off the shelf parts?
Drop in replacement with new features with some parts transplanted from an original SMS, or a from ground up new machine with off the shelf parts?
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VajSkids Consoles
- Posts: 123
- Joined: Tue Jul 07, 2020 10:22 am
Re: SMSII Mainboard prototype public release
Oh - i wanted to make one from scratch! You can get the VDP new off ali express and I got 2 I/O controllers from a random chinese site - and they seem fine! It has the pause hack integrated into the board so you just solder in the gate. Easy!kamiboy wrote:What was the motivation for making a new board?
Drop in replacement with new features with some parts transplanted from an original SMS, or a from ground up new machine with off the shelf parts?
I did lose patience and transplant a VDP as the VDP isn't here yet.
These quad inline packages are a nightmare and the only sockets I can find have a MOQ in the thousands. Not only that, but they're in Germany - my last few orders from Germany have being cancelled due to the current corona virus issue.
TBH i don't get jailbars on my modded systems, but a quick google and youtube will show you the extent people go to to get rid of them when they are there!
Basically i wanted to see if I could keep the clock traces away from anything video related (which there's less of as it contains no onboard video encoder) and see if I could get a perfectly clean picture! It's also using the highest tolerance/ quality capacitors I could find, and just looks sweet + I wanted to get a bit more proficient at Kicad which I just picked up a couple months back.
Re: SMSII Mainboard prototype public release
Is it designed to fit into any existing SMS shell?
In any regard it sounds like a fun hobbyist kit, to build ones own Master System from the ground up. There are many similar kits for vintage computer systems, why not one for a console?
Good luck with mustering the motivation to complete this. Perhaps now that it is made available for all the community could give a hand in completing it.
Cheers
In any regard it sounds like a fun hobbyist kit, to build ones own Master System from the ground up. There are many similar kits for vintage computer systems, why not one for a console?
Good luck with mustering the motivation to complete this. Perhaps now that it is made available for all the community could give a hand in completing it.
Cheers
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VajSkids Consoles
- Posts: 123
- Joined: Tue Jul 07, 2020 10:22 am
Re: SMSII Mainboard prototype public release
yeah the 0402 components were good fun.
The solder doesn't just take to it instantly like the larger components - no matter what flux i tried (I have jelly and a thick liquid one thats too hard to clean but is great flux and a more watery liquid one i tend to favour)
They're so tiny you try and keep them in place with tweezers but then accidentally move them, or they stick to the iron. I got 6 down of my initial 10 pack then had to get more lol (lost them)
Got them all on there - should have protoyped without bypass caps at all ! Or used 100nf like other systems but the board wouldn't look so nice. The 56pf clock caps are 0402 as well..
Had a quick look over some pinouts and the board yesterday actually - off a quick run through and double check I can't find a reason for it to load the BIOS/BIOS's perfectly and run alex kidd etc but not load a cartridge... a 32k cart doesn't look like it requires half as many connections as that so a good way would be to get 32k carts running first and see what is wrong after that.
The solder doesn't just take to it instantly like the larger components - no matter what flux i tried (I have jelly and a thick liquid one thats too hard to clean but is great flux and a more watery liquid one i tend to favour)
They're so tiny you try and keep them in place with tweezers but then accidentally move them, or they stick to the iron. I got 6 down of my initial 10 pack then had to get more lol (lost them)
Got them all on there - should have protoyped without bypass caps at all ! Or used 100nf like other systems but the board wouldn't look so nice. The 56pf clock caps are 0402 as well..
Had a quick look over some pinouts and the board yesterday actually - off a quick run through and double check I can't find a reason for it to load the BIOS/BIOS's perfectly and run alex kidd etc but not load a cartridge... a 32k cart doesn't look like it requires half as many connections as that so a good way would be to get 32k carts running first and see what is wrong after that.