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Identify IC PlayStation 1 on PU-18 motherboard

helakustorm

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Hy,

I've had a modchip installed in this PlayStation 1 SCPH-55xx and that pad trace from that IC have broken; the pad is no longer there, the trace still exist.
Can someone help me identifying this IC and that pad? (I saw that the pad doesn't go somewhere else, it goes only to that pin on the IC)
PS1-55xx-motherboard.png

It has a serial 118 728.

P.S. this picture was taken from other source.

Thanks!

FINDINGS:
------------

I saw that pin 5 from the modchip was connected to that pad on the IC.

I think that pin 5 on the modchip is called gate_wfck (I'm not 100% sure) and that IC on the picture is:
IC 706IC with 4 analog circuitsA3821 8109 (SIDE B), uPC5023GR-compatible

My question are:
1. for what is used gate_wfck on a PlayStation? It has something to do with the region, cd-rom, video or the frequency clock of the modchip?
2. if pin 5 is left unsoldered what symptoms can you have on the PlayStation? Some games will not work?

By the way, the modchip is a PIC12C508/P. Another thing, pins 2, 3 and 7 are not connected anywhere. I don't know if this is a MM3 or a Mayumi modchip.

Thanks!
 
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Trimesh

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The chip is a semi-custom IC specially made for the PS1. It's part of the circuit that detects the wobble groove data on the disc to identify original discs.

That gate/wfck signal has two functions depending on the type of board it's installed on - on the older boards (including the PU-18) it's used as a gate signal to shut off the original wobble groove data. On the newer boards, it's a clock input (Write Frame Clock) that's used to chop up the transmitted data.

The most likely effect of it being disconnected is that the console will boot only copies and not original discs - when reading an original disc, the wobble data on the disc will interfere with the data being sent by the modchip and the result will be corrupted nonsense that the mechacon can't decode.
 

helakustorm

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So, for someone that doesn't want to play originals, only backups, he can let that pin unsoldered without worrying that backups will not work correctly.

As always the best :)

Best regards Trimesh!
 

Trimesh

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Correct - if you don't have any original discs then you can just leave that pin floating.
 

daifuku74

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Hello everyone. I am trying to salvage a PU-18 board that was butchered with a questionable modchip install. The person I bought from obviously didn't talk about the damage... The pad inside the red square from helakustorm's picture ("what that pin does?") is completely gone. Can a kind soul indicate indicate me what I should connect to pin10 of the chip to eliminate the need for the surface pad that's gone? btw I don't understand how this pad connects to something else since there is no via in its path. Thank you for your help!
 

Trimesh

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Hello everyone. I am trying to salvage a PU-18 board that was butchered with a questionable modchip install. The person I bought from obviously didn't talk about the damage... The pad inside the red square from helakustorm's picture ("what that pin does?") is completely gone. Can a kind soul indicate indicate me what I should connect to pin10 of the chip to eliminate the need for the surface pad that's gone? btw I don't understand how this pad connects to something else since there is no via in its path. Thank you for your help!

You don't need to connect anything to it - it does, indeed, just wire to pin 10 of the chip. If you are installing a modchip that uses pin 10 then just wire to the pin itself - if you aren't installing a modchip then you can just ignore the lifted pad.
 

daifuku74

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Thank you Trimesh for your valuable information. So what is the purpose of this pad that leads nowhere? Is that a test point or something?
I reworked the board the best I could, but the machine will only read original PS1 data discs as audio discs. I found there was a burnt trace between C722 and C723 on the other side, so I replaced them both and made a jumper to replace the trace, but no luck. I guess IC706 is blown due to the massive solder bridge that was on several of its legs originally. Is there any way to source a replacement chip besides finding a donor PU-18? Also, what will happen if I install a modchip at this point? Will it boot only backups and no originals? or something else? Thank you
 

Trimesh

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Thank you Trimesh for your valuable information. So what is the purpose of this pad that leads nowhere? Is that a test point or something?
I reworked the board the best I could, but the machine will only read original PS1 data discs as audio discs. I found there was a burnt trace between C722 and C723 on the other side, so I replaced them both and made a jumper to replace the trace, but no luck. I guess IC706 is blown due to the massive solder bridge that was on several of its legs originally. Is there any way to source a replacement chip besides finding a donor PU-18? Also, what will happen if I install a modchip at this point? Will it boot only backups and no originals? or something else? Thank you

I don't honestly know - I suspect that it and the pad below it are an unoccupied PCB footprint for some component, but I've never seen anything (except modchip wiring) actually soldered to it.

Even if that chip is nonfunctional, the console should still be capable of booting both originals and copies with a modchip installed, since it's sole purpose is to process the wobble groove signal from the CD. If you find it's not working then you can try completely removing the chip from the PCB - although this will obviously inhibit the ability to boot originals with the chip disabled.
 

daifuku74

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Correct modchip installation makes it work, originals and backups too, with IC706 unsoldered.
You're the man Trimesh! Thanks a lot
 
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