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PostPosted: Mon Jun 05, 2017 1:18 am 
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Hi there, this is my first message on board.

I have a HVC-CPU-07 Famicom and I tried to do AV mod yesterday. Everything was seemed fine after mod, but unfortunately I touched PPU's few legs with screwdriver when console is running and probably PPU is damaged. Graphics are glitched right now (like this: image from another user's post).

It's probably caused by PPU or SRAM failure, right?

Getting another Famicom is really expensive here. As you may know, some UMC chips easily found from Aliexpress (UA6527P cpu, UA6538 ppu).

Can I use these UA6538 as replacement on my Famicom? Is it compatible to original 2C02?

Also can you suggest SRAM chip for my Famicom?

My Famicom's board photo is attached to this entry.

Thanks in advance.


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PostPosted: Mon Jun 05, 2017 2:34 am 
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Joined: Sun Jun 12, 2011 12:06 pm
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Location: Poland
1. I think you broke the PPU, I talked few weeks ago to guy who also was playing with PPU and oscilloscope (probably he shortcircuited some legs) and PPU started to occasionally display artefacts (in fact it looked like in some moments of playing unused OAM sprites had random x/y/value). After replacing PPU, all started to worked

It looks like nametables aren't properly displayed so maybe there is chance that VRAM is broken instead

2. use UA6528, UA6538 is for PAL, but Famicom is NTSC.

3. Hard to find 2K sram nowadays (especially in narrow package). What I was doing when fixing is to replace ordinary 2K sram with 6264 8K / 62256 32K (which has 4 pins more) and tie them to VCC, you will also need to do some wiring with !WR.


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PostPosted: Mon Jun 05, 2017 3:14 am 
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@krzysiobal good to hear that, thank you! :)

I've checked Lidnariq's wiki page after my question. UA6528 is true chip, you're right.

My Famicom has 2 different SRAM chips: first one is MB8416A-15-SK, second one is 6116ASP-12. Can I use 2x MB8416A-15-SK as replacement for two chips (or 2x 6116ASP-12)? Are they identical? Asking this because I found seller for MB8416A-15-SK from alibaba.

krzysiobal wrote:
1. I think you broke the PPU, I talked few weeks ago to guy who also was playing with PPU and oscilloscope (probably he shortcircuited some legs) and PPU started to occasionally display artefacts (in fact it looked like in some moments of playing unused OAM sprites had random x/y/value). After replacing PPU, all started to worked

It looks like nametables aren't properly displayed so maybe there is chance that VRAM is broken instead

2. use UA6528, UA6538 is for PAL, but Famicom is NTSC.

3. Hard to find 2K sram nowadays (especially in narrow package). What I was doing when fixing is to replace ordinary 2K sram with 6264 8K / 62256 32K (which has 4 pins more) and tie them to VCC, you will also need to do some wiring with !WR.


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PostPosted: Mon Jun 05, 2017 4:04 am 
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Location: Poland
several wrote:
first one is MB8416A-15-SK, second one is 6116ASP-12. Can I use 2x MB8416A-15-SK as replacement for two chips (or 2x 6116ASP-12)? Are they identical?

Yes.


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PostPosted: Mon Jun 05, 2017 4:33 am 
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Thank you so much!

krzysiobal wrote:
Yes.


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