Problems modding a PSX 5552 model

[keropi]

AAAAArrrrggghhhh this is making me crazy!
After all those years I decided to finally install modchips to my 2 PSX systems and get rid of bootdisks once and for all... so I made my own multimode3 chips. Both my PSX systems have PU-18 motherboards.
Installed the chip to the 1st one, it was an instant success: us/jap games boot fine 

But the 2nd one.... it always dumps me to the AUDIO PLAYER!!!!  no matter how many times I installed the chip, not matter if I did the normal or stealth install, putting a game always dumps me to the audio player screen...

Here is the proper diagram (that works fine on my other PU-18 PSX)



and here is my install after countless times of soldering/desoldering in my attempt to make it work (I even tried some alternative points I found in other diagrams without success)



note that this system was never tampered with, never opened and never modified in any way (can't say the same for the other PSX that works - I got it 2nd hand some years ago...)

Any info/idea would be greatly appreciated, thanks! 

[l_oliveira]

You need to check if the PIC is programmed properly and some of the PIC programs are REGION specific.

Just to be informative, the board has zero tolerance regarding piracy devices, even if you're intending to use it as just region free mod.

[keropi]

I did made a simple check: took out the PIC from the working console, it still did not function. Then I took the PIC back to the working console and it was still working as expected... I start to think that this PSX might be broken in some way... 

[l_oliveira]

I said that some pics are programmed with code that works only on a single region of the console. Are you sure your console match the PIC you have ? NOT ALL MODCHIPS work on all regions of the hardware.

[keropi]

I have program mine with the PAL code, since both my PSX machines are PAL....

[l_oliveira]

I have program mine with the PAL code, since both my PSX machines are PAL....

Remove the chip from the supposedly bad machine and have a go with an original disc.

Well, the modchip works by injecting the ASCII code "SCEE" through an input pin of that MC68HC05 microcontroller (the chip with leads on the 4 sides on the picture).

The small chip right under it is part of the drive analogic circuit is supposed to separate the "SCEE" signal from the disc  wooble information. If the signal is detected by the MC68HC05 microcontroller (mechacon) it sends "SCEE" to the data buffer, the bios on the main CPU reads it and prints at the bottom of the screen (even if it does not match the displayed text in case of a wrong region disc.  That "SCEE" is both the copy protection and region protection).  

If the console is working properly, the mechanism I explained should work fine and an original disc should boot. In the case an original isn't booting, you should check for broken traces on the points modchips are soldered.