Famicom av mod instructions?

[famiav]

Ok, I do what you say to me (220uF 1uF ceramic +) = no difference, I still have these bars, they are not refined ...

[famiav]

http://imageshack.us/photo/my-images/43/12042012101.jpg  . Yes, I have a voltmeter, but  I do not know anything special in electronics and I do not know me use this device ....

[famiav]

Yes, that's what I put as my electronic components for video output ... But with this mod  , you have no jail bars ?  or they are fine?
Post Merge: April 12, 2012, 06:10:52 am
Sorry, 47 uF is for my audio output, for video output, i used a 220 uF, I do this schematic, i've got a beautiful image, better of my AV Famicom, look at my message : http://www.famicomworld.com/forum/index.php?topic=4713.msg109867#msg109867

[famiav]

I've got beetween pin 1 and pin 2 : 5,07 V
Post Merge: April 12, 2012, 06:45:53 am
I just put my line on the square "VIDEO" instead of pine PPU: I always jail bar, but the image is darker and more "runny" beurk... I will resolder my wire could before because he was there, the picture is really disgusting

[famiav]

Ok and if I replace this by a resistance of 330 R, what is the difference? because I did not have much material for desoldering so I wanted to know if it was really useful.

I do not know the brand of my capacitors, they are different brands.

Finally, I no longer believe that I can easily remove these bars, I think I'll wait for a clear, precise, easy, and that really works ...

[Da Bear]

Picture with black vinyl tape is "big mess of wires".

Of course it's a mess, it's my "trial and error" board. Trying my best with the small knowledge I have.

What is revision of PPU? E or G?

Revision E.
I found out that 1uF ceramic capacitor between pin 22 and pin 20(GND) almost solved the problem and adding 220uF in parallel doesn't change things much. Filtering power lines doesen't change things much. Picture improved, but on the big, especially blue, areas you still can see jail bars. Or maybe i am just too fussy or my TV too sharp?

Revision G have different PCB layout and pin 22 connected to +5V. however grounding pin 22 with 1uF ceramic capacitor almost removed jailbars.

If this is result of EMI, shield over the PPU should help. Will try this little bit later.
And i think i won  This 8Mpix image looks awful scaled, but in 100% scale you can roughly see, what i've got. Should try another camera.


CORRECTED
I think jail bars are result of noise from CPU on power line. You need to ground pin 40 CPU via  ceramic capacitor. I used 1uF capacitor. By the way just one extra 220uF capacitor in the right place will reduce jail bars quite a lot. I tried to feed PPU via LC filter, but no visible changes.

Ha! My poor old TV and it's picture settings All good for now. I am finally satisfied.

It's a rev E PPU.

Yes, jailbars come from noise in the power line. Have you traced the noise to the CPU itself? I might give it another go with the oscilloscope when I have more time.

As a sidenote, even the NES have a lot of noise in the power line. But there are no visible jailbars in the AV out and I have noticed that the NES picture is much brighter then the Famicom.
I would like to see on an oscilloscope how the AV Famicom behaves.

[Da Bear]

Very interesting, I'll take a look and make some of my very scientific rewiring
What I noticed before was that the noise is only present when a game is running, so we might be a few steps closer now to isolate the source of the jailbars.

Size matters, ask any girl

[jpx72]

Oh I enjoy your enedeavours guys, I hope you will make some tutorials for different revision boards in the future!

[famifan]

80sFREAK, are you going to show us the pics of your modded famicom MoBo? it will be rather helpfull for everyone

[famifan]

performed the same trick as 80sFREAK has done, soldered a lot of SMD 10uF caps on the power lines, about 15 pcs.

don't feel differencies/improvement, maybe because i cut some tracks a long time ago. Will try to solder Q1 again and use his av mod schematic.

Any throughts on this?

[famifan]

I don't think they are 10uF. Where do you take video signal from?

i don't think they are 10uF too, but when i measured everyone the capacistance meter showed right about 10uF.
have 2 meters, and they both agreed on 10uF, only few pcs have 8-9uF instead of 10, but this is really not the case. For the instance i checked a few 10uF el caps, they all have 10-11uF, so i totally relied on my measurements.

i didn't buy they just desoldered from broken PC MoBo (GA-8IPE1000-G)

video signal is taken from the lifted out from the PCB 21-st PPU pin and buffered by NPN transitor.

[famifan]

video signal is taken from the lifted out from the PCB 21-st PPU pin and buffered by NPN transitor.

can you draw the circuit with exactly parts you have?

already done this, please consider the picture  http://www.famicomworld.com/forum/index.php?action=dlattach;topic=4713.0;attach=1584;image
(rectangular boxes are resistors)

transistors: KT3107E and KT3102E (i'm sorry that datasheets on this crap is russian only) - just low-power general purpose transistors, nothing special.
Post Merge: April 22, 2012, 10:18:38 am

ok than, maybe just lower voltage than mine.

and for what voltage are yours?

[famifan]

thanks!

my transistors are okay, replacing them by another general purpose transistors changes nothing.

i lifted the pin because after lifting i see some improvements on the jailbars.

So, how the "2 transistors" works for you? is it better or worse? i guess that nothing changes.

[Da Bear]

Did some more testing this weekend.
Hooked up an AV Famicom to the oscilloscope and there was noise even in that board. Though it was mush less than the old Famicom it's still there.

Also lifted the power-pin from CPU and feed it separately from the Famicom with a bunch of caps but that didn't make any difference either.

A really good (and clumsy) power supply did make the lines fainter. But who wants a power supply bigger than the Famicom itself?

[Da Bear]

Haha, nice! Watching Super Mario running on the oscilloscope was fun to

Have not shielded the PPU. Might try that later. Finding time is my issue