Famicom AV Mod with garbled screen.

[Dzordz]

Hi all, I've done the Famicom AV mod but I always get a garbled screen when trying to turn on the console. However, the sound is fine.

Details: I don't know which kind of model is the Famicom cause the back of the console shows it's HVC-002 and the box shows it's HVC-001 (I suppose that it's a HVC-002). The board shows the next kind of CPU: HVC-CPU-07:



I've tried 4 different mods and only works these with the same result: garbled screen.

1. http://www002.upp.so-net.ne.jp/jsrc/densi/fcav.html -> But I use a 4,7uF capacitor instead of 0,47uF as suggest in this website. The transistor I use is NPN 2SC1815 as suggest this website http://www.briconsola.com/esp/p23.htm (and the same site too).

2. http://nfggames.com/forum2/index.php?topic=4055.0 -> I use a 3x300ohm in serie, and 82ohm the other resistor. It just works like the other mod: garbled screen.

The 2 mods I've tried that it didn't work are:

3. http://www.briconsola.com/esp/p23.htm

4. http://old8bits.blogspot.com.es/2013/03/famicom-mod-av-para-el-modelo-esquemas.html

I tried to change the transistor to a BC546 but with this It didn't work (it shows black screen).

I don't know where can be the problem (maybe PPU ?). I've been researching in some forums but I can't find the solution.

Pictures (The game is Rockman 5, but I've been trying with Double Dragon II, Ninja Ryukenden, Punchout with the same results):







Picture of the mod (it can be confuse but I REALLY follow the next scheme)





Video:

View My Video

Thank you in advance !!!!

[80sFREAK]

Be sure, that slot is clean. This graphics issue has nothing to do with video circuitry.

[Dzordz]

Be sure, that slot is clean. This graphics issue has nothing to do with video circuitry.

Hi, thank you for your advice but how could I know if the slot is clean ? I've cleaned the cartridges but I don't know how to check if the slot is clean or not.
Post Merge: May 06, 2013, 05:38:12 pm
I've tried to clean as it suggested here, but it doesn't seem to work. There's the same f******* garbled screen

http://www.youtube.com/watch?v=bWg2k736KZ4

[famifan]

if you checked the slot connectivity there is definitely something wrong with CHR part. Try to check decoder and SRAM

[Dzordz]

if you checked the slot connectivity there is definitely something wrong with CHR part. Try to check decoder and SRAM

Hi, I've checked this PDF http://www.benheck.com/Downloads/NES_Famicom_Pinouts.pdf to identify the CHR's points and I think I know where are all these pins ... but I'm sorry, What have i to do now whis this pins ? Thanks.

[P]

It's strange that all your games have the exact problem so you might want to check your Famicom as well. Begin with a continuity check with a multimeter between these and other points.

[Dzordz]

It's strange that all your games have the exact problem so you might want to check your Famicom as well. Begin with a continuity check with a multimeter between these and other points.

Ok, I'll begin now with my tester. I'll notify you when I finish.
Post Merge: May 07, 2013, 02:20:53 pm
All is OK :S I don't know where can be the problem ... maybe the PPU is blown ?

[Gippy44]

I'm experiencing the same issue, did you ever figure this out?

[famifan]

I'm experiencing the same issue, did you ever figure this out?

i got the system with the same issue too.

http://www.famicomworld.com/forum/index.php?topic=12651.0 (i pucrhased the system from that thread)

i'm going to get UMC drop-in replacement for PPU fro aliexpress just like http://www.famicomworld.com/forum/index.php?topic=13029.0