3DO RGB mod (3DO adventures part 3)

So following on from my previous adventures in 3DO where we found that 240p could be achieved with the BT9103 encoder https://assemblergames.com/threads/240p-output-on-3do-with-bt9103-encoder.66295/. The next step was to explore viable solutions for achieving a RGB output on the 3DO. As we know, the 3DO is unable to output RGBs natively (with the possible exception of the Creative Labs 3DO Blaster, citation needed). Previously the only option was to use Otakus Stores RGB mod but the store doesn't seem to be active/ available. So the next logical step was to search for or create an updated version of the mod. A total of 6 RGB 24bit 3 channel encoders were reviewed and the prime candidates were Rohm technologies BU3616K and Linear technologies ADV7125. Given the more simple and cheaper qualities, I settled on the BU3616K.

All we needed from the motherboard were 24bit RGB, sync, clk, 5v and GND. Using the datasheet for the similar BT856 encoder, we could tap the necessary signals we needed.



Next a PCB was designed, including an LM1881 sync stripper to obtain pure Csync from Luma.



Then the wires were soldered to the original BT9103 encoder



Alternatively there are vias near the CLIO chip that can be soldered too.







The result was good. The only issue was a slight horizontal shift of the image which can be resolved with further circuitry.



Unfortunately I don't have a capture card so the picture is on a camera so the image isn't perfect.

The next step will be so remove the BT9103 chip and replace with an RGB capable BT9107 chip, the pinout should be almost identical and will allow an RGB native 3DO.

I will make the final pcb design available once final tests have been completed.

Some testers have already kindly tried this design out and confirmed that it works on the VP536 encoder as well as the BT9103 encoder. Once the design has been confirmed to work on the BT9101 encoder, this design will be good for all models of 3DO (excluding Creative Labs 3DO Blaster and later Panasonic FZ-10 with the Anvil chip).

Edit:

More pictures uploaded. I've also edited the original board to include 220uF AC coupling capacitors on the RGB lines and a 480 Ohm resistor on the CSYNC out line to attenuate the TTL signal for TV receiver.



My original design had these in the SCART connector. This design is useful for people without the components in the SCART. For those with custom SCART cables, please refer to the original design.

Original Board available here https://oshpark.com/projects/JkzC7wJ7
Revised Board available here https://oshpark.com/projects/3VUzE6t5

 

Great stuff!

 

Why don't you add a plcc socket (you need to adjust the pinout as you are installing the chip upside down and rotated) so it's mostly plug and play?

Also that chip was used a long time ago, I saw a tutorial on a Japanese page. I even bought some, but didn't get my hands on a 3do yet.

 

Dang I have exactly the same idea.
It's been a year or so all the piece are laying around my apparement and I'm too busy to work on it. T_T

 

Thank you for the comments. I know I'm not the first to use the BU3626K to encode RGB for 3DO, I started to research different encoders and then realised it had been used in the past by a Japanese modder and also @airs from assemblergames. The Japanese modder used a 44pin QFP breakout board so I wanted to design a simple purpose made pcb to keep it tidy and include an LM1881 for Sync stripping. The idea of a 68 plcc socket is good for ease of install, I'm not sure how secure it would be for permanent install. I also thought of using different QSBs for the different encoders and keeping the same main design with a 28pin ffc connector.

I just wanted to put a simple design out there so people could use as is or modify to suit their needs. It would be interesting to see people's ideas. This encoder has only been used for VP536 encoders in the past but now we know the pinouts of the other encoders, this design will be suitable for all 3DO.

Cool. I definitely recommend finishing a design. 3DO with RGB out looks rather nice. I've been working on this since July and just wanted to get the basic mod out there. I will post more pictures and eagle files after the weekend.

 

Plcc sockets work well long term. Amiga community have been doing it for years.

The neobiosmasta also took the same approach

 

Edit: More pictures and Eagle files added to original post. Feel free to adapt and use to your needs.

 

Ok, finally got around to adding more content to this mod. I can confirm that this mod works on all 3DO encoders (excluding Anvil chip). A very big thanks to @kimaq and @Self_Control_Me for testing this mod on their VP536 and BT9101 encoders. Pics of BT9101 installation thanks to @Self_Control_Me.








Composite


RGB

I've also added a jumper to select between Luma and CSYNC just in case the user already has a sync stripper in their cable.

Here is a link to the oshpark board if anyone wants to order one for themselves.

https://oshpark.com/shared_projects/4CEnH9uI

If anyone wants a pre-made board ready to go, send me a PM and I will make some up if the demand is good.

And here are the new Eagle files if anyone wants to alter to their needs

 

Wow, great job!

 

Hey, I saw your post about buying a premade 3DO RGB board. I am interested in getting one. Would you be willing to do the install as well if I shipped it to you and paid labor etc?

Thanks,
Jordan Chastant

 

This doesn't have any horizontal shift fix right?

 

That is correct. This mod doesn't address any horizontal shift. It varies from setup to setup. I know you and another member on AtariAge are looking into solutions. This mod would need the picture adjusted at the TV/ monitor if there is any horizontal shift.

 

I was sorta hoping you had figured it out. I still haven't come up with a solution that doesn't have side effects. I've sat the project on the back burner for a little bit. Need a break from it.

 

Hey Taji could you try contacting me again on videogameperfection? I tried replying to your e-mail but it just bounces.

 

Sorry, I haven't managed to find a solution yet. I've been looking for an IC that can do the job. the amount of shift varies so a fixed value solution might not suit every setup but potentiometers are noisy. I know what u mean, sometimes u need to step away and come back with a fresh head.

PM'd

 

Great work Taiji, very tidy.

 

The 3do is always going to need a pot to adjust the shifted image

 

This is because the RGB mod uses a separate DAC to produce the analogue RGB but still uses the sync from the original DAC. The different pipeline delays causes a timing skew.

Some setups get it more than others. The problem is using pots can cause noise and unwanted sync issues. If u own an OSSC, u can adjust the horizontal position with that.

By using a 24 bit RGB DAC that also generates its own sync, u will get analogue RGB which doesn't suffer from horizontal shift.

Watch this space.

 

Any updates? Is this still the best solution for RGB mod'ing a 3DO? Or has somebody developed a board using a DAC that generates csync to address the RGB to sync timing issue?

 

I found a fz1 service manual and skimming through it I had a neat idea. It shows the pinouts for the controller port. I was thinking there is a way to mod controllers without audio jacks to have audio jacks. Either by taking a female db9 and wiring up l&r audio to pins 3&4 of the db9 with some sort of a pot for volume & plugging that into a jp2x p2 port or wiring something inside the controllers that don't have a p2 port, like the nakitech ones.
Just a thought.