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PostPosted: Sat Jun 22, 2019 1:39 pm 
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Hi! I am new to this forum and also new to modifying/fixing snes consoles. I have my original SHVC NTSC console from the United States which I bought many years ago. It has always worked perfectly until a few months ago when the video image suddenly lost all colors and got an inverted (negative) black and white picture. I am connecting my snes to my HDTV through an RGB SCART cable connected to an OSSC line doubler. The cables and OSSC are not the issue because I have tested them with my RGB-modded SNES mini console and have not had a problem.

I have tried to fix the issue by doing the following:

Replaced all smd capacitors with brand new capacitors bought from console5.
Replaced the 21.4772 crystal oscillator with a brand new one.
Checked connectivity of everything that I could test on the mother board, but found no issues.
Replaced the voltage regulator with a 5-volts, 2 amp regulator bought from console5 as well.

Since none of the above seemed to fix the problem, I tried soldering pins 20, 21 and 22 from the BA6592F video encoder directly to the corresponding RGB pins of the multi-out through a cable and 75ohm resistors, and did the same for the csync, but connected it directly without a resistor.

After this, I still got the same black and white inverted (negative) image.

I then tried soldering a 470 uf, 6.3 v capacitor to legs 2 and 3 of the voltage regulator. Amazingly, I got just a tiny bit of colors; blue and yellow (which were in incorrect places), but the rest was still black and white and the image was still inverted (what is supposed to be in dark colors shows as white and what is supposed to be in light colors shows as black.

I am wondering if what I have is a faulty CPU or PPU1, PPU2. Any ideas? Have anybody had this problem before? I would hate to throw away this console, it has a sentimental value to me!!


Attachments:
File comment: After soldering the 470uf capacitor
IMG_20190622_183523.jpg
IMG_20190622_183523.jpg [ 1.92 MiB | Viewed 5834 times ]
File comment: Before soldering the 470uf capacitor
IMG_20190622_183848.jpg
IMG_20190622_183848.jpg [ 2.08 MiB | Viewed 5834 times ]
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PostPosted: Sat Jun 22, 2019 2:22 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
Since the picture seems to be mostly right, but with wrong colors, I'd assume it's a broken PPU2 (which contains the palette memory)


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PostPosted: Sat Jun 22, 2019 3:55 pm 
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Is it too complicated to replace the PPU2? Where can I get one?


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PostPosted: Sat Jun 22, 2019 4:22 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
SMD rework is something that people can do without too much risk to the parts involved. It helps to have the right specialty hardware, and a lot of practice ahead of time.

As far as sources of PPU2s ... only other SNESes.

A while ago, DogP made a nice writeup of various SNES parts failures, and using SNESes to repair the rarer (but almost identical) NSS.


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PostPosted: Mon Jun 24, 2019 3:07 am 
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Joined: Sat Jun 22, 2019 1:06 pm
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Hi, thank you so much for answering! I got lucky and was able to buy a PAL version of the 1-chip01 snes console from Ebay for about 30 Euros. My plan is to mod the board to be able to play both, PAL and NTSC cartridges and install it inside the outer shell of my broken SHVC snes console. Does anybody knows exactly what do I need to make this mod? I have basic soldering and unsoldering tools and some 21.47 hz crystals.


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PostPosted: Mon Jun 24, 2019 8:50 am 
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Location: Seattle
I remember the differences between PAL and NTSC for 3chip SNESes, but I don't remember what changes are necessary on a 1chip SNES. There's this old thread...


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PostPosted: Thu Aug 01, 2019 3:16 am 
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Joined: Sat Jun 22, 2019 1:06 pm
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Hi!
Thank you for posting the link to the old thread, it has been very helpful. I am almost done with the mod; I connected almost everything, but I still have a question. Is the 2.2kOhm resistor, which is necessary between the CPU and the 5-volt line, also necessary between the 5 volt line and pin 9 of the video encoder and pin 4 of the lockout chip?

I was going to connect these two pins directly through the switch to the 5-volt line without a resistor, but want to avoid damaging any of these chips if I do it without a resistor.

I'll post some pictures when I'm done with the mod, and explain everything I did in case somebody else here in the forum needs the info.

Thanks!

Alfredo


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PostPosted: Thu Aug 01, 2019 11:24 am 
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I'm afraid I have no idea what you're talking about - would you link to the exact posts you're using as reference?


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PostPosted: Thu Aug 08, 2019 2:59 am 
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Joined: Sat Jun 22, 2019 1:06 pm
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No worries, I figured it out! I did not need the resistors for those connections after all. I am now done with the mod and it works flawlessly; no color or graphic issues. I will be posting pictures this afternoon and a little diagram of how it works.

cheers


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