▲ 14 r/consolemodding
Master System 2: Complete Recap and New Audio Circuit
u/Impossible_Current35 — 4 days ago
u/Impossible_Current35
▲ 7 r/consolemodding
I’ve improved the board of my AV Famicom
First of all, please excuse me if anything is unclear—I’m new to electronics and I’m using a translator.
I bought an AV Famicom from China with the NESRGB clone already installed, and when I used it with my Everdrive N8, it produced a terrible humming noise, along with a lot of video interference. After analyzing it, I saw many areas for improvement and decided to rebuild most of it based on my own ideas.
In summary, I’ve made the following modifications:
- I replaced all the ceramic decoupling capacitors on the board—originally 10nF—with 100nF X7R MLCCs; there are 12 in total.
- I replaced the original 7805 with a 1.5A LM340T5.
- I soldered a 47uF electrolytic capacitor to the 7805 input to correct the poor design of the input power rail.
- I increased the capacitance of the 7805 output electrolytic capacitor from 1uF to 220uF
- I added a 100uF + 100nF polymer capacitor to the second main power rail on the board, just past the cartridge port. Based on my measurements of the board, this rail runs through the cartridge’s secondary power pin, and I can’t see where it goes from there because the board is covered and there are no publicly available schematics, however, I suspect it powers the crystal circuit and the memory chips.
- For CPU decoupling, I soldered a 100uF + 100nF electrolytic capacitor.
- To decouple the PPU, I soldered a 1uF MLCC directly to the PPU’s 5V pin and left the original decoupling capacitor at 100nF. Since the latter is located 12mm away from the PPU, it is not effective for decoupling, which is why I soldered directly to the PPU’s power pin.
- I discovered that using the video ground for the audio on the AV port’s common ground causes audio interference. Therefore, I cut the original audio trace and added an RCA port (Rean, Neutrik), connecting it directly to the audio circuit’s output with a shielded AWG24 cable. I obtained the ground by lifting the solder mask and soldering to the board’s ground plane (see images)
- I have replaced the audio coupling capacitors with audio-grade capacitors
I also modified the original power supply since it has a center-tapped transformer and a two-diode bridge, which is quite good and uncommon in linear console power supplies:
- I replaced the original electrolytic capacitor and increased its capacity to 3300uF (audio grade)
- I added an additional 220nF CBB at the output of the rectifier bridge
- I shortened the DC cable to approximately 25 cm and wrapped Kapton tape around the transformer’s laminate.
The improvement in audio and video quality is dramatic; the RGB video output is now very clean, and I’ve managed to reduce background noise in the audio by more than 23dB—probably even more—in addition to eliminating intermodulation and improving audio linearity without using any bypasses and with only minor modifications to the board, so I’m very happy with the result.
It’s likely that by obtaining actual schematics of the board and conducting a more in-depth analysis, a few more things could be corrected, but at this point, without making more aggressive modifications, any further improvement will be marginal.
I captured the audio output after completing the improvements, with the EverDrive connected. Reddit's compression makes the audio sound distorted:
I've also uploaded the audio to Google Drive in case you want to listen to it without any loss of quality:
https://drive.google.com/file/d/1-ucVv0zwxrlxUd7CHy_IqxRAr2oNtUE4/view?usp=sharing
https://drive.google.com/file/d/1lqKK7pMnlwd_-idQX_pI2ns_hkcXCJ5b/view?usp=sharing
- Tokkyuu Shirei Solbrain (Shatterhand):
https://reddit.com/link/1t8q884/video/e7tpu09oqc0h1/player
- Teenage Mutant Ninja Turtles III:
u/Impossible_Current35 — 12 days ago
▲ 0 r/consolerepair
Mi super famicom tenía interferencias y zumbidos en el audio así que he cambiado los condensadores y he realizado algunas modificaciones y correcciones en la placa y fuente de alimentación original. Para ser la primera vez que sueldo electrolíticos radiales en superficie creo que todo ha quedado bastante solido.
Tras analizar los esquemas he realizado las siguientes modificaciones y correcciones:
Donde iban los electrolíticos SMD he soldado radiales estandar de muy bajo ESR y con una tolerancia de voltaje mucho mayor que los originales y en C62 (botón de reset) he soldado un cerámico 1206 de 2,2uF.
La consola usa 4 condensadores de 100uF para los acoplamientos de video, 2 en paralelo para la señal de Luma y otros 2 en paralelo para la señal CVBS, los he sustituido por 2 electrolíticos de 220uF que es mucho mas limpio que el diseño original.
He cambiado el regulador lineal 7805 por un LM340T5 y he mejorado el desacoplo de la salida del mismo soldando un electrolítico de 100uF en los pines del regulador.
He aumentado C63 (Filtrado y desacoplamiento de entrada del 7805 ) y C64 (Base del transistor C2412) a 47uF.
He puesto una ferrita de 3,5mm en el cable del interruptor.
En cuanto a la fuente de alimentación he sustituido el electrolitico original y lo he aumentado a 3300uF (Grado de audio), he añadido un CBB adicional de 220nF en la salida del puente rectificador y he acortado el cable a 25cm aprox.
u/Impossible_Current35 — 24 days ago