Famicom av mod instructions?

[2A03]

if you cut and up carefuly the leg 21 and solder of top separate to the motherboard, reduced the jailbars to minimun

I just did this to my Fami today and it didn't change anything. I'll see if I can get a reading from the voltage regulator when I can and maybe replace it with a new 7805.

[Da Bear]

Hey Da bear,
I have a model that is doing the same thing.  One thing I did find is that the buzzing would totally disappear when controller 2 was not attached.  As soon as it was attached it came back.  I know it was not the controller as I have a few spares and they all did it.  Try this and let me know if the buzzing goes away.

The problem is not in the controllers since I have not had them attached at all to this board.

I believe it will. That increase is insignificant. I have famiclones that run on 9V without any voltage regulator (they run fine on 5V too).

I have measured my current modded FC, but I haven't desoldered the original transistor. It had strong jailbars so I attached the capacitor on the PPU and they dissapeared. The voltage on 7805 is 5,01 - 5,02V. My setup (it's HVC-CPU-GPM-02C)

I'm gonna try change the voltage regulator to one I know gives 5v+ to see if it makes any difference.

I also read something about building a filter between PPU pin #22 and the Xtal here: http://www.famicomworld.com/forum/index.php?topic=3093.0
Anyone know how this filter looks like and how to properly connect it?

Edit: I see that you are using shielded cables but you havn't connected the shield to ground. Am I right?

[jpx72]

Hmm this is what "NTSC 2C02 technical reference" by Brad Taylor says about pin 22:

/SYNC: this signal when zero, will force the status of colorburst control,
scanline and pixel counters/flip-flops used inside the PPU to definite
states. Generally, this is the means of which two 2C02s connected together
in a master-slave config (via the EXT bus) can syncronize together; the
master PPU's /VBL line feeds the vblank information to the slave's /SYNC
input. On Famicom consoles, this pin is always tied to logical one. On the
NES however, this pin is tied in with the 2A03's reset input, and as a
result, the picture is always disabled while the reset switch is held in on
an NES.

I am not reading there anything about any filter amp...

I couldn't figure out the circuit around pin 22 on NES from the available NES schematics (too blurry)...but probably it's connected together with CPU pin 3 (RST) and then connects after CIC near the reset switch...

EDIT: It may be a lone shot but if pin 22 is connected to logical 1, then you can try to desolder it from the PCB and insert a 0,57 - 1k resistor between the pin and VCC. Maybe one small capacitor between the pin and GND too...

[Da Bear]

I have now replaced the 1000uF capacitor, voltage regulator and xtal. No difference in jail bars, back to square one I guess
But the buzzing noise dissapeared when i changed the voltage regulator, always something.

[Da Bear]

Okey guys!
Some more discoveries on pin #22!

I found this site yesterday. The mod is just about the same as the one where using here with the exception of a capacitor between PPU #22 and GND (PPU #20)
http://translate.google.se/translate?sl=de&tl=en&js=n&prev=_t&hl=sv&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fplayoffline.wordpress.com%2Fmod%2Foldfcfba%2F

I had another Famicom that gave bad lines so I soldered a 100uF capacitor (did't have 47uF as above site suggested) over #22 and #20 and the lines became very very faint with a crappy built AV board. They tend to get even fainter when I get them fully assembled.

Please note that I'm still NOT using ANY capacitor over +5v and GND.

Just mind the polarity of the capacitor!


Yes, I've removed the trace from #21 to Q1 completely.
Post Merge: November 03, 2011, 05:34:09 am
Oh...forgot to mention this.

If you hear a buzzing noise from the speakers and it's not the mic in controller 2 thats faulty it's probably the power switch that have bad/dirty contacts inside. Jerk it back and forth to clean the oxide inside and the noise should disappear.
Post Merge: November 03, 2011, 08:15:32 am
Updat on the capacitor between #22 and #20.
I managed to find one 47uF and I soldered it into my Famicom that gave very very faint lines (very hard to see) and now I can not see any lines at all from that machine. None!

I have tested this on 2 machines now, one with very bad lines, and one with very faint lines.
The "bad" machine with capacitor now gives as faint lines as the good machine without capacitor. The good machine with capacitor = no lines!

jpx72: Maybe time to update your guide on your homepage?

[2A03]

Nice discovery, I'm going to try that on my Famicom and see if it helps. Maybe I'll even try it on my top loader and see if I can get line-free video out of it.

[jpx72]

I managed to find one 47uF and I soldered it into my Famicom that gave very very faint lines (very hard to see) and now I can not see any lines at all from that machine. None!
jpx72: Maybe time to update your guide on your homepage?

Hey very nice!
I would still be curious to know the results of desoldering the RST pin (#22) and inserting the resistor there, in combination with the capacitor you've placed there too. This:

This way it would be pretty close to a NES ciruitry.
Maybe you can try it on the "bad" machiine, just be carefull not to break the pin22.

[2A03]

Tried the capacitor on both my Famicom and NES top loader as well as a top loader I modded for someone on Sega-16. I can't say it's completely eliminated the lines, but it has reduced them significantly, especially on the top loaders.

[jpx72]

My setup (it's HVC-CPU-GPM-02C)

Edit: I see that you are using shielded cables but you haven't connected the shield to ground. Am I right?

Forgot to answer you on this - the shielding is grounded, it's just not visible on the photo.  Also the R110 and C220u are not visible there, because I soldered them near the cinches (on the other side of the cable that goes from my famicom).

2A03 - thanks for the feedback! I will definitely try it too!

[Da Bear]

I'll make a try with the resistor.
Post Merge: November 04, 2011, 05:25:36 am
So, I lifted pin 22 from the board and soldered the resistor between the pin and +5v and the capacitor between GND and pin 22.
Result: The lines came back 

Refitted the pin and my capacitor and the lines became faint again.

[jpx72]

Thank you for the test! Oh isn't that great when somebody helps with testing ideas?

So this is not the right way...  Ok, I'll post my results when I test the #22-47uF-#20 on my setup. Will try both with #20-1000uF-#40 and without it.

[Da Bear]

All here make's a great modding team. Knowledge is nothing if you can't share it

When you are on it, try caps from 47uF to 220uF on #22-#20. I don't think it makes any difference with bigger cap, but who knows.

[NintendoKing]

Tried the capacitor on both my Famicom and NES top loader as well as a top loader I modded for someone on Sega-16. I can't say it's completely eliminated the lines, but it has reduced them significantly, especially on the top loaders.

That right there is a break-thru! I would love my NES Toploader to have that mod for sure!

[Xious]

As I recall, part of my research pointed to the lines being caused by the signals of PPU Pin 25 (A13) becoming commingled with the ground plane. If you draw a video signal directly from A13 (may have been Aq2), you will notice vertical bars that overlay exactly where the stripes fall. This video contamination is what I was, and am (when I get back to it) working to rectify.

To test this, wire your A/V board to everything but the video signal, and connect the lead from your amplifier (that normally goes to 2C02-p.21 'Video') to 2C02-p.25 'A13' and look at the video display from that signal. Compare it to the position of the lines, and you will see exactly what I mean in vivid detail. The A13 signal travels very close to GND in several places, so re-routing it is possible, but extensive.

(I didn't go that route, although I played with the idea, as it is not ideal. You'd need to life the traces and use shielded jumpers to connect the paths by hand in order to change it. I'm exploring other options...)

You may want to play around with this information...  Use it as you see fit: Perhaps you will find it useful, as the best way to fix this problem is to circumvent the cause, not merely deal with the symptoms.

[2A03]

Tried the capacitor on both my Famicom and NES top loader as well as a top loader I modded for someone on Sega-16. I can't say it's completely eliminated the lines, but it has reduced them significantly, especially on the top loaders.

That right there is a break-thru! I would love my NES Toploader to have that mod for sure!

That can be arranged if you'd like...