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I have opened a few Playstation 2 consoles to fix or clean them so far and I have never seen this weird little board before. It is connected to where the ribbon cable for the front panel (power/reset and eject buttons) usually goes and to a 2-pin connector that is usually for a cable that comes from the optical drive. Now those two cables are instead connected to that board.

It really looks like a hardware patch to fix some sort of problem of this particular motherboard revision. There is also a slight possibility that this is homemade, who knows.

The PS2 that this comes from is a PAL SCPH-30003 with motherboard revision GH-012, sub-revision 1-682-236-11.

Motherboard:

enter image description here

Weird little board connected to the motherboard:

enter image description here

Zoom on the little board (front):

enter image description here

Zoom on the little board (back):

enter image description here

user3840170
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olliebulle
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  • IIRC the red/black is simply power. Otherwise it could be anything from delayed reset to locking the eject. – Raffzahn Dec 21 '23 at 09:48
  • @Raffzahn If I’m reading the PS2 service manuals correctly, that connection should be for the limit switch that indicates the tray is open by shorting a specific control line to ground. – Austin Hemmelgarn Dec 21 '23 at 13:22

3 Answers3

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This is the v4 PnP Key, an early solderless modchip that was used in combination with a swap disc to play import or backup games.

enter image description here

There was also the v5/v6/v7 version that could be hooked to newer PS2 revisions where the optical drive was using only flat cables.

enter image description here

I found the information by using the Wayback machine on a modchip store's website and browsing during the years that the PS2 was relevant. Here is the link for the curious ones: mod-chip.com in 2004

Thanks to @kouta-kun and @Mark Morgan Lloyd for pointing me in the right direction. Since I am very familiar with how traditional PS2 modchips work and are installed, I did not even suspect that this board could be one.

olliebulle
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That seems to be a modded PS2. The "12C508A" is a PIC often used in modchip boards for both PS2 and PSX. Sadly I can only find info about that specific modchip from other people asking about it1 so it seems to be a pretty niche variation (and not a common one like say, the Matrix mod).

1:

Laurel
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kouta-kun
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    Yep, even if it weren’t for the fact that the visible BOM looks like it’s for a modchip, stuff like this where a small board is installed inline with one or more connections is almost always a modchip in older game consoles. Dynamically rewriting data on the fly is just about the only practical option for any kind of complex mod in such systems. – Austin Hemmelgarn Dec 21 '23 at 12:36
  • @AustinHemmelgarn actually now that you mention rewriting data it does seem like it's not in a position to be useful for a modchip. Most mods I've seen need access to some sort of bus, while this only seems to intermediate the power/eject buttons according to OP. Maybe some sort of help for magic swap? – kouta-kun Dec 21 '23 at 12:58
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    Not just the power/eject buttons, but if I’m reading the service manual correctly, also the switch that indicates when the tray is open (that seems to be the wired connection it’s intercepting). My guess is that it’s something designed to trigger a specific bug in the controller for the optical drive, which may in turn translate to helping with Magic Swap, or may just be to trigger a specific type of glitch for stuff like speed running. – Austin Hemmelgarn Dec 21 '23 at 13:25
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I'm not a gamer but it looks like a sibling of "Unknown 6" on The Playstation 2 Modchip Archive:

chip lower left corner

The visible differences appear to relate to how the power is brought onto/off the PCB.

Laurel
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Mark Morgan Lloyd
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    Please augment the answer with an explanation of the purpose of the modification. Otherwise it is a link-only answer, which is discouraged. – Leo B. Dec 21 '23 at 22:24