Worklog PS1 Native VGA mod (15khz)

Wesk

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I recently picked up a SCPH5502 model PS1 for the intention of pairing with a PSIO. As my main CRT only has composite or component video input I felt I was required to purchase the HD Retrovision component cables to get the best video quality.

However the retrovision cables are quite pricey at over $70aud and I already have a VGA to Component transcoder (Which I use to get 15khz component out of my Dreamcast) so I did some quick searching and found that the PS1's GPU actually has H and V sync readily available.

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So I figured I'd take a roll on it and see if I could get native 15khz VGA. Using shielded coaxial wire I ran from the RGB lines and used some kynar for the sync lines.

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And well...it just worked. Razor sharp 15khz VGA natively from a PS1.

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Next step is to remove the system link port from the PS1 mainboard and design a mounting mechanism.
 

Wesk

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So here is the final design on the VGA mount, the top piece is designed so that when the case is closed there is just enough pressure on the top of the port that it won't move vertically.

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Wiring has been tidied up:

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Unfortunately due to the height of the VGA port the top shielding needs to be trimmed to accommodate it:

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A final look at the rear + bonus image:

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And here is a comparison between the standard composite output and the VGA modded output:

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STL's of the VGA mount have been provided if you want to have a go at this yourself. Your mileage may vary however as the vias for H & V sync will be different depending on the board revision but will remain the same on the GPU.

Now all I have to do is wait for the PSIO to ship....
 

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buzzyc

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Following Wesk's guide, I was able to successfully mod my SCPH55xx (PU-18) PS1 as well.
Although I don't have a 15Khz CRT at home, I stumbled upon this wiki and was delighted to see that I have 2 monitors at home that support 15Khz inputs:
List of modern monitors that support 15 kHz analog RGB signals - 15 kHz RGB Video (wikidot.com)
My BenQ GH24DHD and Acer KH2711 both successfully display the PS1's image. Interestingly it must be left in FULL display mode to work. Changing the picture type to something like Aspect or Pixel removes the 15Khz support, and all that is shown is "Out of Range"

Wiring to the VGA port isn't as clean as I'd have liked - but after an hour of desoldering and resoldering to determine the RGB order it got a little messy. Trust me though, no shorts, despite what the image may suggest

20210206_191908-reize.jpg


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To save everyone else the hassle, I have color coded the RGB points on the 55x board:
InkedBottom_LI (2).jpg


Here are a couple nice side by side's in the classic that is Disney's Hercules. Composite on Left, VGA on Right,
20210207_093412-Composite-Resize.jpg
20210207_093425-VGA-Resize.jpg


And finally because we're just tapping into the multi-out, the delightful side bonus that you can run Multi-out and VGA in parallel, allowing for real time side by sides comparisons!

20210207_095552-resize.jpg


Big thanks to Wesk for helping me out during this mod, and assisting with troubleshooting and validating everything!
I have a 7502 I plan to mod next, and will provide the H&V pad locations once found.
 
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Awesome work!

But since I am a noob with video signals, could post an image of pinout with numbers or colors, please? (Both main board and vga connector).

Cheers.
 

Wesk

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Awesome work!

But since I am a noob with video signals, could post an image of pinout with numbers or colors, please? (Both main board and vga connector).

Cheers.
@buzzyc has already provided an image with the colour line locations:
InkedBottom_LI (2).jpg


And Here is an image of the VGA port from the rear (Solder side)
6642fd5ea1f8aa45558f16785408f092.jpg
 

cfc_12

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How about the H&V on a PS1 Slim?

Btw, why didn't you use a PS1 Slim since its board is much smaller?
 

Wesk

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How about the H&V on a PS1 Slim?
No idea as I believe it uses a slightly different GPU package, you'll need to do some research.

Btw, why didn't you use a PS1 Slim since its board is much smaller?
Because this is the version I own? The PSones also lack the expansion port required to use SD loaders like a PSIO.


[EDIT]

A 2min wiki search shows that the pinout on the package is the same for the PSone GPU

 
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Stitches

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No idea as I believe it uses a slightly different GPU package, you'll need to do some research.


Because this is the version I own? The PSones also lack the expansion port required to use SD loaders like a PSIO.


[EDIT]

A 2min wiki search shows that the pinout on the package is the same for the PSone GPU

How about the H&V on a PS1 Slim?

Btw, why didn't you use a PS1 Slim since its board is much smaller?
The IC that handles the serial port still exists on both PSOne revisions, so you can wire a PSIO to a PSOne. It's just a lot of fiddly magnet wire and trace cutting bullshit, and there's no particularly neat way to do it without removing the CD drive.

Does give me an idea for the next build contest tho
 

Wesk

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The IC that handles the serial port still exists on both PSOne revisions, so you can wire a PSIO to a PSOne. It's just a lot of fiddly magnet wire and trace cutting bullshit, and there's no particularly neat way to do it without removing the CD drive.

Does give me an idea for the next build contest tho
Wasn't the access to the port disabled in the BIOS of systems that didn't have the port?
 

Stitches

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Wasn't the access to the port disabled in the BIOS of systems that didn't have the port?
Not sure about that, but this guy managed to do it and left enough documentation that it should be replicatable. He did it with 2 board revisions, but I just found out there are possibly 2 more revisions that aren't documented in the thread. So it might be a case of early revisions work, later ones don't?
 

Wesk

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Not sure about that, but this guy managed to do it and left enough documentation that it should be replicatable. He did it with 2 board revisions, but I just found out there are possibly 2 more revisions that aren't documented in the thread. So it might be a case of early revisions work, later ones don't?
If that's the case it might be time to design a flex.
 
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