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PostPosted: Tue Feb 14, 2017 12:46 pm 
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Hello Everyone,

I'm brand spanking new here. Found this looking around for some information on what's going on with my NES when I'm attempting the initial stages of a Hi-Def NES install. Seems like the people here are some of the best to ask.

I've done the cap replacement in the Power/RF module. The system started up just fine after, so that was a great sign. I then proceeded to desolder the PPU and CPU. This was my first attempt at such an ambitious desolder job, but otherwise I'm pretty comfortable with an Iron. After some work, I was able to get the chips out and the new sockets mounted. When I put the chips into the new sockets, I get the dreaded blank white/pink screen when powering it on. I've checked continuity between the Chip pins and the opposite side of the motherboard and I get the continuity I expected just fine. At that point, I ran out of time and haven't yet returned to the project.

With those symptoms does anyone have any suggestions on what the culprit may be? This is the original 72-pin connector, but I've never had trouble with it in the past and it fired up without hassle before the removal of the PPU/CPU. Does that behavior suggest problems with either specifically the PPU or CPU so I know which to focus on first? I found a schematic online, it's the one with the orange background. I was thinking of checking continuity with the pin connections listed between the pin connector and CPU/PPU. Is that a reasonable place to start?

Any suggestions greatly welcomed and appreciated,

Noch


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PostPosted: Thu Feb 16, 2017 8:25 am 
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Joined: Tue Feb 14, 2017 11:39 am
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Here's some more information that will hopefully help. Last night, using the schematics I found and my eyeballs, I did continuity testing between each pin on the PPU and CPU and the other devices. I did get successful continuity between the parts I could identify on the schematic or the next VIA along the trace for ones where the label was illegible. So it appears that there aren't any broken traces. I then lightly tinned each pin on the motherboard for the 72-pin connector to make sure they had good contact as they had a couple scratches from removing/reinserting the connector. I'm still getting the blank white screen. One time I turned it on, I had a few video artifacts beyond the complete white screen.

Have I fried one/both of the CPU/PPU chips?


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PostPosted: Fri Feb 17, 2017 9:04 am 
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Going on the assumption that I have indeed damaged my PPU and/or CPU in my poor attempt to safely remove them from my motherboard, Where would people suggest getting new ones these days?

I've been looking around on evilbay and CL for the bare chips and/or other consoles. No luck on bare chips and consoles are very pricey in these places. I'm nervous about buying another system though and destroying more chips in another fruitless attempt at this mod.


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PostPosted: Sat Feb 18, 2017 10:50 am 
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I had similar problems on the past.
In fact, it was a problem with the socket itself, that I could only spot by testing it with the connected IC and touching the probes on the top part of the IC's terminal and in the botton of the board.

I never had a fried CPU or PPU from just removing it from the board, but maybe you could try some clone CPU/PPU pair, try searching for UA6527 and UA6528. They're NTSC clone CPU/PPU respectivelly. Unfortunatelly they have some issues :-(.

I've found some clone pairs cheap here.
The real thing is pretty more expensive, here and here.

A wish you the best!!


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PostPosted: Mon Feb 20, 2017 12:14 pm 
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Joined: Tue Feb 14, 2017 11:39 am
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Thanks,

On that advice, I did double check connectivity from each of the IC pins to the bottom of the board and that passed with flying colors. In the mean time, I did order some clone chips from AliExpress. It's fine if they're a little wonky if I'm mostly using them to test if the board is fine.

I've also won an auction for a Pace desoldering station. It's older but should be a nice unit. I'm now determined to get good at this without breaking stuff and getting a quality tool never hurts. Unfortunately, it doesn't help with the current situation.


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