SOLVED: black screen with 60hz/no composite after crystal mod

General information to do with the PlayStation 1 Hardware. Including modchips, pinouts, rare or obscure development equipment, etc.
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kaliki
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SOLVED: black screen with 60hz/no composite after crystal mod

Post by kaliki » May 28th, 2020, 4:03 am

Hi everyone, I am new here, I usually do mods but not much into ps1 but modchipped them several times and psio installed a couple ones without any problems.

yesterday I tried to do add c-sync and ntsc crystal mod on a pu-22 I already modchipped times ago with mayumi v4 I think (it was working ok)

c-sync: no problem at all, video was displaying

then i tried to do the crystal mod and something went wrong, I cut trace going to pin 196 of gpu and feed it via 220ohm with a 53.69 mhz crystal taken from a ntsc mega drive (i took 5v from the av pinout)

I noticed that after ps logo screen things go black, so I put everything like was before this but I have black screen and no games running with ntsc games, pal games play fine.

If I go back with sync on composite video I noticed that I got no more composite signal (luma and c sync work)

I probably did something wrong as I see that xtal on board is 17.73 and not the 53.203 but I cant understand why I have these problems now, someone could help me understandin this?

thanks

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really dont understand where was my fault but now everything works....I put high pin 13 of video encoder, and powered the ntsc mega drive xtal with 3.3v (i tought it worked only with 5v), I m quite happy cos wasted hours yesterday troubleshooting...still dont know if composite now works but I dont give a f has c sync is working nice

rama3
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Re: SOLVED: black screen with 60hz/no composite after crystal mod

Post by rama3 » June 2nd, 2020, 12:08 am

You probably followed a tutorial for PU-18 or ealier boards.
Your PU-22 is very different, as you noticed with the 17.73 oscillator feeding a PLL, that then generates the required system clocks.

Your PU-22 can be modified, but you need to keep the PLL circuit for PAL mode.
For NTSC mode, you need to disconnect the "N" pin on the gpu and connect it to your 53.69 oscillator.
Watch out though: the 9000 series service manual has the "N" and "P" pins reversed.

So these are the crucial points:
Disconnect the correct GPU clock input pin (by default the N and P inputs are linked!), and feed in your external clock.

kaliki
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Joined: May 27th, 2020, 4:24 pm

Re: SOLVED: black screen with 60hz/no composite after crystal mod

Post by kaliki » June 6th, 2020, 3:33 am

Thanks for your reply, actually I got 53.69 mhz oscillator feeding both 196 and 192 pins, probably the pins u refer as p and n and things seem to work perfectly

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