help needed with sort-of-working-but-not-quite-yet-av-mod

[omega-xis]

Hi there,

I recently received a famicom from someone which we want to pace at events throughout the Netherlands, we only have one problem: all our TV's are HDMI-only 
we do however have AV->HDMI upscalers to deal with retro-consoles, therefore I decided to AV-mod my famicom.
we followed this guide:
http://www002.upp.so-net.ne.jp/jsrc/densi/fcav.html
since it uses the exact same HVC-CPU-07 motherboard.
After installation this is what we ended up with:
https://www.dropbox.com/s/1gnw0jboc013pvy/av-mod.mp4?dl=0
I looked at the schematics from the av-mods from this forum and it appears that they use different resistors and no capacitor, so what should I do?

[famifan]

hi

according to the b/w picture it definitely looks like there's something wrong with video amplifier. The signal is too weak, so the TV can't even recognize the color subcarrier and produces only very dark and unstable image.

I believe that every AV mod schematic will do basically the same, even if the schematic could be quite different. As long as video is amplified correctly it will just work fine on the most of TVs.

Do you have other transistors around as I highly doubt the installed one is doing its job fine? Could you try a different schematic?

Does your AV-HDMI upscaler work with other devices fine?

[omega-xis]

Hi there,

I can try a different schematic but then I need to order extra parts. I'm thinking the 22Kohm resistors are a bit too much.
I'm using the 2N3904BU-TO92 transistor with a 47uF capacitor as described in the tutorial from the link.

Yes the AV upscaler works perfectly with other devices. I also tried routing the AV signal through my analog audio mixer to amplify the signal which makes the picture a little more clear, but far from perfect.

is the problem the video amp from the famicom itself or from my mod?

[famifan]

is the problem the video amp from the famicom itself or from my mod?

sorry for confusing, under video amp i mean the part of AV mod circuitry related to the video part of the signal.

i think, there's a problem with the mod. faulty transistor or wrong pinout maybe?

[FAMICOM_87]

try this way
http://jpx72web.blogspot.bg/search?q=famicom+AV
I tested it worked well , and you do have to disable RF

[omega-xis]

ok so I stared at it for a long time and discovered my transistor was wired wrongly, now it's the correct way in I get this:
https://www.dropbox.com/s/o706u9o5p7su3kq/VID_20170605_115535.mp4?dl=0
Still a lot of interference, does that have to do with the RF still being connected?

[FAMICOM_87]

It looks like a broken PPU  what about RF is it distorted like AV mod?

[omega-xis]

cant really test R/F i don't have the switch-box. which is why i'm AV-modding it.