Famicom av mod instructions?

[Da Bear]

If you don't mind desoldering the transistor 2SA937 originally used in the Famicom you should use that one. It's marked Q1 on the motherboard and placed next to the PPU.

[Xious]

That one can't answer, as the truth is non-conclusive. I personally think that a few NPN transistors have the best quality; others swear by PNP. The reality is that it is very subjective, and that ultimately, 'best quality' is based on too many factors, especially personal opinion. In truth, for this type of application, NPN and PNP are essentially identical.

PNP and NPN don't in and of themselves make any prominent difference; the actual frequency ranges, and the waveforms involved differ between different models and materials, but I won't say that the physical charge makes a difference, aside from how it's implemented / integrated (e.g. direction of flow).

You can buy a selection of RF video amps and see which you prefer. In fact, you could build it around a 12BY7 vacuum tube (as I'm considering doing for my own amusement) if you desire...

For now, you need to correct the flaws in your existing installation. before worrying about transistor types.

P.S. I thought that the first (and most early) Dendy models were RF only, PAL units... Essentially complete clones of the Taiwan Famicom, of very close; maybe like the FC with a Makko kit.  I'll need to look at that again.

P.P.S. I honestly don't see the appeal either of desoldering the '937 or of reusing it. Additionally, you will most certainly need to re-wire the entire modification if you do. Simply removing Q1 will cut the feed of video to the RF modulator, and thus to the video bridge, which is where you have connected your existing modification. I think that if you fix the problems as I outlined before, you will be fine...

You never did clarify if your video problem was the distortion (wavy lines),  like the status / life bar area on your photo, or if it is something else you are seeing.

[Padoca]

Hi everyone, i tried this mod today, and got decent results with a couple problems as follow

The major problem is a green bar around the middle of the screen, getting some ghost effect from graphics around the right side of the screen:

http://www.youtube.com/watch?v=Dvt6pUehv-s


EDIT:
Made another vid where its more visible

http://www.youtube.com/watch?v=er7f5IydKbo

And of course i have the vertical bars, tried using a 470uf and 1000uf capacitors betwen 40# and 20#, with no results, and a 100uf  betwen 22# and #40, nothing too:

http://www.youtube.com/watch?v=0W__hI1oG28&;


They are far more visible than show in the video due all the reflection on the TV



The bars doenst bother me much at the moment, you can only see then in games with light colors like Kirby and Mario. That green bar in the middle appears only when theres a black backgroung.

[Pikkon]

For one did you try your famicom on a crt tv instead of a flatscreen.

[kokie]

So , is there anyone suscessfully modded their system vertical line - free with out problem? CAn you please write the instruction for your mod.

[famifan]

Dendy
No. Dendy have AV. Dendy is shit.

why did you think so?

original 'dendy classic' have both AV and RF outputs and provide clear lineless picture on the AV. No annoying jailbars!
Main dendy's disadvantage is PAL system which plays game more slower than on NTSC system due to another framerate.
Post Merge: January 18, 2012, 10:39:19 am

What kind of PNP transistors have best picture quality?

by the way, the cheap general purpose low-power low-voltage transistors were used in famicom video circuit. And they work like a charm!

personally, i use for AV-modding kt3102 and kt3107 - they had similar functional characteristics. And they are cheap, too!

if you want to use better transistors just try to find out similar transistors with the lower noise output level then original one have.

[famifan]

just adding 2 cents from my own av-modding experience.

i've used video amp circuit from famous Dendy famiclone, because it has correct brightness and color signal level.

only shielded cables were used and Q1 (2SA937) were desoldered from the PCB.

initialy, the circuit were connected directly to PPU 21st pin and image still contains recognizable vertical lines.
but after video_out pin were lifted out from the PCB, the lines had become more unnoticeable, then before.

all pictures are attached.

[Domino82]

Could someone who has done this recently do me a huge favor and please post *exactly* what parts they used (and where they got them if at all possible)? With the details given on the guide, when I go to look for the transistor, resistors, and capacitors, the number of different options are mind-boggling. Perhaps those other details don't matter, but I'd rather use *exactly* the same parts as someone else who has successfully done this, if you know what I mean.

Many thanks!!

[Da Bear]

This is what I use when I AV mod Famicom

1 x 300 ohm resistor
1 x 110 ohm resistor
1 x 220uF capacitor
1x 2SA937 transistor from the Famicom (Q1)

Optionally add an extra 220 uF capacitor that you solder between PPU pin #22 and #20 to reduce some jail bars. I also remove the trace between PPU pin #21 and Q1.

[jpx72]

For my HVC-GMP-02C I am using these for the video part:
BC 178  - PNP tranzistor
330 ohm resistor (couldn't find 300)
120 ohm resistor
220 ohm capacitor (for 16V)

For the jailbars:
470 uF between PPU pins #20 and #40. Trace between PPU pin #21 and Q1 NOT removed, not even cut.

For the audio output I have added a 47 uF (10V) capacitor:
output  o-------- -[47uF]+ ------o Famicom

Everything bought in local electro shop. I'm used to services there, those guys can always help and give possible alternatives.

[famifan]

mine is hvc-cpu-07 rev.07 bоard

1) Q1 is desoldered,
2) PPU pin #21 is lifted out of the PCB
3) 1500uF aluminium electrolytic capacitor + 0.1uF ceramic capacitor between PPU power pins.

part:
1) 1 x KT3107E - PNP transistor (replace parts are BC 212, BC 556, 2SA970, 2SA1049, and others)
2) 1 x KT3102E - NPN complementary transistor for KT3102E
3) 2 x 220 Ohm resistor
4) 1 x 2200 Ohm resistor
5) 1 x 75 Ohm resistor
6) shielded signal cables

this circuit drives 75 Ohm output load that is more preferable for all tv sets.

audio is connected directly to the #46 cartridge pin.

[jpx72]

About the audio output - when connected directly to #46 cartridge pin, by connecting this output to audio card of a PC, there is only buzzing sound. So adding the sound output capacitor is a good idea.

[famifan]

most of the audio capture devices have capacitors on the inputs, unless you are using extreme professional hi-fi systems ^_^

So adding the sound output capacitor is a good idea.

yes, the idea is good. This capacitor is used only for removing the DC current from signal.
i dunno how it can remove buzzing sound, because any sound that you hear contains only the AC waveforms.

http://ompldr.org/vY3M0cQ/btdd_fc.ogg here my sample. Normal FC sound with little interference from video signals.

[jpx72]

i dunno how it can remove buzzing sound, because any sound that you here contains only the AC waveforms.

I am not talking about low buzzing sound in the background, but completely buzzed output (not hearing any melody). Maybe it's not affecting all sound cards, but probably all on-board ones. Sometimes it's needed to electrically (galvanically) separate two electrical components (in this situation Famicom and PC card), and that can be done with adding a capacitor between them (to compensate two different ground potentials).

[bitmerge6502]

I just bought a famicom from EBAY & tried several mods with no luck . It is a model: HVC-001, board revision: HVC-CPU-07 (1984, but mine has the 1983 RF modulator?), serial # H7766073. I am currently trying kyuusaku's mod because Da Bear is using it & it looks as he has the same model Famicom as me. Before I did anything I  hooked it to a NTSC tv (several LDCs then then tried later on CRT) via RF on cable channel  U.S.A. 95 & 96). picture & sound come in fine on all TVs i tried (albeit picture is fuzzy & has interference, but my RF RCA plug is tarnished). Then when I tried my 1st mod, i can get a (faint) picture, but it is not stable, skewed, and wrong colors. from my EE experience it looks like a different tv system or wrong Hz, but i got it working using RF & model# seems correct U.S.A. & I purchased it from a Japanese ebay seller (not HK). I do have a computer monitor that will do PAL, but it will tell me with the on screen display which tv system it uses if it switches to PAL (which it doesn't). I tried different spots on pcb to tap video (& ran it direct from pin21 to RCA in on TV), isolated pin 21 & removed OEM transistor (2SA937). i tried different spots for ground & separated spots to ground video shield & mod transistor ground. i tried various mods; using pnp/npn variations. even doing these things, i still get roughly the same signal, just different degrees of distortion & interference of the video signal. I'm almost at the end of my "wits' end" & don't want to buy a kit if i'm just making a simple mistake or am just ignorant of some obscure knowledge about the particular famicom I'm using. I am also worried if i do buy a kit & still have bad luck. one other thing i noticed is I'm using a generic PSU made for USA NES it outputs 9vdc (unlike the OEM ac/ac PSU) @ 850ma. I also used the SEGA Genesis (1st gen, model MK-1602) AC adapter (9vdc, 1.2A). but my meter only gives 4.8v on the voltage regulator. So I replaced the 7805 regulator (Radio Shack# 276-1770) & it now reads 5.0vdc, but did noting at all to improve picture (in fact, i saw no change at all). I also heard problems with U.S.A. being 110vac & japan being 100vac. But I think i eliminated this problem by using a U.S.A. ac/dc (rectified) transformer & new regulator it shouldn't matter, correct? Seems like as long as I'm still getting a clean 5v on the board it shouldn't interfere? I also noticed the PPU (RP2C02E) & CPU (RP2A03-E) is the same as a U.S.A. NES I have laying around for parts. I am considering swapping them (PPU first), & see how both systems are affected. My parts NES is already socketed from the time when I was about to add a "Copy Nes" from RetroZone. If that doesn't help, I'm at a loss. I might also try replacing the caps on the voltage regulator circuit & any that are inline with ground-->VCC and ground-->video. I know the Famicom works, so If this problem just becomes an unexplained mystery, I will just restore the OEM RF & make due.  I specialize in mostly digital electronics, so video is somewhat new to me. I would appreciate any experienced advice or info anyone could give me. [I'll add pictures as necessary]