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Homebrew ColecoVision replacement mainboard


fieroluke

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On 10/21/2021 at 1:29 AM, fieroluke said:

Actually I haven’t. Since my board will contain at least some of the SGM capabilities including RAM and sound (so hopefully some SGM games will run on it), and the expansion bus on my board only supports the Atari expansion module I’m not sure how Opcode Games will feel about it.

 

If you work out a licensing fee with him he would likely be fine on the original SGM side, or at least that's what I believe eventually happened with the CollectorVision Phoenix. I don't know about the SGM2 as it isn't out yet and it is designed to output its own video.

 

This is a really cool project you have put together. Lots of people have talked about it but to see someone actually do it is cool.

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2 hours ago, zaphro72 said:

If you work out a licensing fee with him he would likely be fine on the original SGM side, or at least that's what I believe eventually happened with the CollectorVision Phoenix. I don't know about the SGM2 as it isn't out yet and it is designed to output its own video.

 

This is a really cool project you have put together. Lots of people have talked about it but to see someone actually do it is cool.

Well, I don’t see the why a licensing fee would be warranted. Adding 32K RAM (the only RAM chips in DIL package that are still available) to a Z80 and implementing one bit from a register to disable the ROM can be credited to the ADAM engineers if anyone. I’ve never even seen an SGM or schematics, so I didn’t copy anything either.

 

Besides, I’m not going to sell these things anyway, at least not built ones. Maybe blank boards at cost. This is a fun project, and it would be cool to be able to run games that support those capabilities, that’s all.

 

Edited by fieroluke
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On 10/22/2021 at 9:59 AM, fieroluke said:

Besides, I’m not going to sell these things anyway, at least not built ones. Maybe blank boards at cost. This is a fun project, and it would be cool to be able to run games that support those capabilities, that’s all.

I would be all/in for populating blank boards. I volunteer as a QA tester.

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Fixed the color issue (intermittent connection of a critical cap)! Big thanks to @Falonn! Now black really is black, saturation could be better, but that may be the TV. 
 

so I’m pretty happy with it now. Adam ram and ay-sound are working, going to test sgm game soon.

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Very cool. Is the video output RGB or composite or both? I think it should be both and use the same Din jack as the model one Sega Genesis, that way SCART (RGB) and composite cables could be shared/readily available.

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Also you should consider putting thru holes to allow original power switch and reset to be installed. A rebuilt power switch is very reliable and I only experienced a reset switch issue a couple times out of many hundreds of consoles I worked on. This allows for a perfect drop in for original case and physical buttons.

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1 hour ago, Yurkie said:

Very cool. Is the video output RGB or composite or both? I think it should be both and use the same Din jack as the model one Sega Genesis, that way SCART (RGB) and composite cables could be shared/readily available.

For NTSC there’s composite output (could be test it, don’t have a 9918), with the 9928/9929 there’s RGB and b/w composite & color composite with the expansion module (again untested because I do have one).

the RGB is the Genesis 2 Mini DIn connector.

 

1 hour ago, Yurkie said:

Also you should consider putting thru holes to allow original power switch and reset to be installed. A rebuilt power switch is very reliable and I only experienced a reset switch issue a couple times out of many hundreds of consoles I worked on. This allows for a perfect drop in for original case and physical buttons.


I actually added that with the next board revision today. Since I can’t get original buttons, there are also replacement buttons that are available today that drop in also.

 

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  • 1 month later...

Rev. B (third iteration) boards showed up today! They look gorgeous as usual, with minor improvements:

 

The board now fits both NTSC and PAL machines, and now the original power switch fits as well as an alternative (similar) switch still being made today. Same goes for reset switches: Coleco original or modern alternative!

 

There are now also two alternative locations to feed power: rear of the console (preferred for PAL machines) or near Controller jack 2, routing cable through stock power jack hole.

 

You can follow the progress at my ColecoVision blog: DIY-ColecoVision

 

 

 

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  • 4 weeks later...
1 hour ago, Nateo said:

Excited to see how this progresses. I have what might be a perfect candidate for a transplant with this board given that the RAM in a CV I've been working on has rusted itself onto the mainboard.

Have you checked out my blog? (Link in post above)

 

im currently testing the expansion module #1. It basically works, but my Genesis 2 cable is hardwired to RGB, so my TV doesn’t switch to Composite when I plug in the expansion module. I get sound but no picture. I do see composite video on my oscilloscope though, so I blame my TV.

 

my Tv only has Scart, so I must come up with adapters to continue testing…

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15 minutes ago, fieroluke said:

Have you checked out my blog? (Link in post above)

 

im currently testing the expansion module #1. It basically works, but my Genesis 2 cable is hardwired to RGB, so my TV doesn’t switch to Composite when I plug in the expansion module. I get sound but no picture. I do see composite video on my oscilloscope though, so I blame my TV.

 

my Tv only has Scart, so I must come up with adapters to continue testing…

So have you been able to test the board on an NTSC TV so far?

 

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23 minutes ago, fieroluke said:

Have you checked out my blog? (Link in post above)

 

im currently testing the expansion module #1. It basically works, but my Genesis 2 cable is hardwired to RGB, so my TV doesn’t switch to Composite when I plug in the expansion module. I get sound but no picture. I do see composite video on my oscilloscope though, so I blame my TV.

 

my Tv only has Scart, so I must come up with adapters to continue testing…

I did check out the blog! And I'm very grateful for your documenting the development of this project!

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44 minutes ago, Pixelboy said:

So have you been able to test the board on an NTSC TV so far?

 

Afaik the TV is Multistandard, but the Coleco is RGB anyway, so the only part that’s NTSC or PAL is the expansion module itself, and I only have a PAL one (and only PAL Atari carts as well)…

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35 minutes ago, fieroluke said:

Afaik the TV is Multistandard, but the Coleco is RGB anyway, so the only part that’s NTSC or PAL is the expansion module itself, and I only have a PAL one (and only PAL Atari carts as well)…

If you need an NTSC EM#1 and a few NTSC Atari 2600 carts, I can help you out.  :)

 

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I have one of @fieroluke’s boards. It is a true work of beauty! Although I am decent with electronics and soldering, populating the board is going to be quite a bit of work for me. I will need to project manage this and break it down into small steps that I can do daily for probably a few weeks. 
 

If the v2 board production is ramping up, I would like to get a group order going for the components. Anyone willing to volunteer to head that up? I would, but I already have a few projects on backlog. 
 

Would love to see a skilled video tutorial for this a la those of @-^CrossBow^-

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I wouldn't mind checking one of these out to see well it works with some my 2 trouble carts that are very picky about the CVs they will work on.

 

And putting together any project like this, you always start with the smallest components and then work your way up from there. If I did a video on something like that it would likely be done similar to how I did the Genesis recap vid where I sped it up from start to finish and barely spoke at all. 

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5 hours ago, phattyboombatty said:

I have one of @fieroluke’s boards. It is a true work of beauty! Although I am decent with electronics and soldering, populating the board is going to be quite a bit of work for me. I will need to project manage this and break it down into small steps that I can do daily for probably a few weeks. 
 

If the v2 board production is ramping up, I would like to get a group order going for the components. Anyone willing to volunteer to head that up? I would, but I already have a few projects on backlog. 
 

Would love to see a skilled video tutorial for this a la those of @-^CrossBow^-

Once I have tested all details of the current version (and this is a spare time thing), I’ll prepare the files to have the boards made including all or the majority of SMT components in China. That‘ll make component sourcing so much easier and building one should be possible in an evening or maybe a weekend.

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  • 2 weeks later...
  • 3 weeks later...

I finally made some progress with my replacement mainboard today! Using a small bios patch, I enabled intrinsic 64K ADAM RAM if no cart is inserted, and wrote a minimalistic cartridge header into RAM at $8000 before retesting for a cartridge. I used a boring Game name and copyright ©2222 because I hand coded the assembly and patched the bios. But the important news is: it worked as planned! 
 

So next I can test the USB port to actually download games through USB from a PC…

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