A/V Mod Problem - lots of White noise

[mada0]

  Well this is my first post in this awesome community that I've been reading for a long time

The problem: I followed this http://jpx72.detailne.sk/modd_files/fc/avmod.htm way to do the A/V mod and It went good, even without the copper thingy the vertical bars were barely noticeable, the thing is, I just got a copy of Metroid FDS version and as soon as I started to play I noticed that the "special effect" sounds were not being played at all , i.e. the Opening / Closing Door "blooop" and all that good stuff.

My FC rev is HVC-CPU-07 I took the sound with the 220mF capacitor from the SOU soldering point at the first time, now I tried to take it from the pin 46 at the cart slot and the Special Effect Sounds are playing but there is no image   (My TRC TV AV channel starts to move like crazy when I put the RCA video cable in, so, I weld again the audio output to the SOU point and the video works perfectly but without the SE sounds.

[jpx72]

I found out that the SOU soldering point is placed before the extra audio from cartridge is mixed in, so you did ok to solder your sound to pin 46.
But you are doing something wrong, video should not be affected by the sound output, have you used the capacitor on the pin 46 too? Check twice where your ground is connected (shielding of the audio cable).

[mada0]

In fact, the image doesnt appear in the TV screen without the sound rca plugged in

Here are some pics of my mod to check if its all correctly done :/

Video Output

As you show, I used the pin 22 as a 5v output.




Sound Output
Red wire goes from GND on the rf unit to the Sound shielding

[2A03]

It looks like you're getting 5V for the video amp from pin 22 of the PPU and not pin 40.

[jpx72]

Pin 22 of the PPU is connected to +5V. Check the schematics, 2A03.

But your mod, mada0, seems ok, are your wires ok too?

[mada0]

In your mod is needed to isolate de Pin 21 and then solder it to Pin B of the A937 in HVC-CPU-XX boards?, cause, I was following the "old" schematic and today I cheked up that u posted a new one.


Actual status:

Sound Ok Np clear as hell:

Video: Only AV Channel flickering and noise when powerup, black screen.

Isolated Pin 21 from PPU soldered to B on Q1, A/V cables checked Video cable shield soldered to C on Q1, Vsignal cable soldered to (-) 33uF capacitor, this one soldered to 100 this one soldered to E on Q1, /150R this last to pin22, +5V taken from 22, and 0.1uF ceramic capacitor between Pin 20 and 22, I dunno what to do more  

[2A03]

EDIT: NM.

[jpx72]

I really don't know where the problem can be. Try pin21 to + on capacitor 33uf and then directly to TV. Shield anywhere on GND. No other components. You should have video, not nice, but at least you can test if it works.

Old and new schematic is the same, only added the isolation of pin 21.

[2A03]

Why not try this mod instead:



I've modded loads of NES top loaders using this circuit and it's never failed me.

[mada0]

I connected pin 21 through capacitor directly to the RCA and the same result, if I connect only the SOUND RCA I get Noise in the TV Speakers, when I put the VIDEO RCA , then the noise stops and the TV AV channel starts to flicker, I turn on the Famicom, and I get crystal clear sound but no image only black screen flickering.

Maybe the HVC-CPU-7 is "special" with some signals?

I checked all +5V points Im getting  4,78V, so Pin 20 is no the problem, and I have signal in all the wires.

[2A03]

The HVC-CPU-07 is really no different than any other Famicom or NES once you've isolated pin 21. Have you tried the circuit I posted?

Also I should mention that the 220 uF cap on the audio is unnecessary, just wire the audio straight up without any extra components.

[80sFREAK]

mada0, are you sure that all parts are alive?

[mada0]

Well the voltage is gettng reduced by the resistors and the capacitors were bought new I checked the continuity so all seems ok   ,I mean if all works when SOU is used to bring out Sound it should mean that all parts are ok, righ? despite the RCA stuff and all.

Im going to try solder sound without capacitor, btw the only thing I didnt do was putting the ferrite bead, but as I saw it was optional I thought it wasnt necessary.

[UPDATE]

Ok, I made up my mind and changed the RCA cables I was using to another ones I got cutting some PSX RCA video cables (I have plenty) and now its working , the video doesnt dissappear when I pull out the RCA sound cable so now its all working fine ^^, it seems that all this problems were thanks to the poor shielding quality of the first ones I used. Thank You everyone for bringing help so fast  

Well, I started to test the games and all went fine... except from Metroid, the game plays and sounds well but when i choose the save option it dont work (one problem after another) I never get the message to change to side A once save the file.

[jpx72]

I thought the problem will be the wires, I once disassembled whole famiclone just to find out that the video wire was simply "degraded" or "disintegrated", it was all black inside, like it was a 100 years old. Was from a chinese clone I bought two years ago. The new chinese materials are really dangerous!

[mada0]

Long time no see, Im modding another Famicom 07 revision and im trying the new diagram, and I have some questions are you 2-3 still here? (2 years later  )
Post Merge: June 09, 2016, 04:24:22 am
I ended doing it right but im having a problem with a lot of white noise