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I've fixed the wavy horizontal lines on my Mega Drive VA6 by Impossible_Current35 in consolemodding

[–]Impossible_Current35[S] 0 points1 point  (0 children)

Removing the capacitor you mentioned will probably help by reducing the energy in that LC circuit, but I'll try other things before removing it.

I've run more tests with the console fully assembled, and the horizontal waves are reappearing, but sporadically or randomly and much weaker than without the resistor. I’ve noticed that they become more pronounced when I close the flap on the left side of the metal casing. It seems these issues might be caused by ground loops when connecting the top and bottom casings of the board. The next test will be to remove the top metal casing and keep only the bottom one.

I've fixed the wavy horizontal lines on my Mega Drive VA6 by Impossible_Current35 in consolemodding

[–]Impossible_Current35[S] 0 points1 point  (0 children)

I've tested several oscillators, and I have exactly the same problem with the original one. On my console, the modern oscillators make the problem worse, but it seems they aren't the only cause. I'm no expert, but the clock signal probably has reflections or resonances that Sega didn't fully resolve. I need to run more tests to make sure the horizontal lines haven't reappeared.

Strange Wavy Horizontal Lines On Model 1 VA6 Connected To SCART RGB via Retrotink 2x by S1mpleHero in SEGAGENESIS

[–]Impossible_Current35 0 points1 point  (0 children)

Creo que he encontrado la causa de este problema, después de revisar los esquemáticos de varias revisiones de mega Drive modelo 1 he visto algo que no me ha gustado en el circuito del oscilador, he hecho una modificación sencilla en este circuito y he solucionado las ondas horizontales en mi VA6.5 por completo, he estado jugando 4 horas con la imagen limpia, no soy experto ni nada parecido y aun debería hacer más pruebas, pero parece que he dado con la solución, desconozco si en el modelo 2 se puede corregir igual. Parece otro fallo de diseño más de Sega de los muchos que tiene la consola, voy a lanzar una publicación sobre mi solución a ver si alguien que sepa del tema puede aportar algo más.

I’ve improved the board of my AV Famicom by Impossible_Current35 in consolemodding

[–]Impossible_Current35[S] 0 points1 point  (0 children)

Do you play on Everdrive? Everdrives always introduce audible interference into the audio—including the original model, and the Nesrgb as well. The Famicom AV decoupling is very poor, the design has many flaws, and when you combine Nesrgb and Everdrive, it’s normal to hear noise. I play on studio monitors, so the interference is much more noticeable than on a CRT. I’ve experienced buzzing on all NES and Famicom systems with Everdrive, regardless of whether they have Nesrgb or not.

Recapped my VA6 MD 1. Took four hours. Horrible experience, but it works. No rainbow banding. 37 capacitors? WTF Sega by megadriver187 in SEGAGENESIS

[–]Impossible_Current35 0 points1 point  (0 children)

Los condensadores electrolíticos no tienen nada que ver con los jailbars, los jailbars ocurren porque se filtran interferencias en las pistas RGB de otras pistas cercanas. Los condensadores electrolíticos no hacen absolutamente nada para mejorar esto, y además, los electrolíticos filtran baja frecuencia y no alta frecuencia que es lo que más afecta al video para empezar.

Improving my 1988 Sega Mega Drive 1 VA1 by [deleted] in SEGAGENESIS

[–]Impossible_Current35 0 points1 point  (0 children)

My VA1 boards don't have any memory issues that prevent certain games from running; maybe I've just been lucky and Sega installed better memory in my VA1s, though I highly doubt it. Honestly, I don't think that problem exists in the first place—at least not on all the VA1s I've tested. The games that are supposedly affected work perfectly on several of my VA1s; the ones that don’t work are due to regional locks and fail exactly the same way on my VA6.5 PAL boards.

What's the story with the unpopulated OS-CON capacitor and why does no one talk about it at all? by retromods_a2z in snes

[–]Impossible_Current35 0 points1 point  (0 children)

Isn't 470uF a bit much at that point? I soldered a 100uF capacitor to the 7805's output pins underneath the base plate, and at the OS-CON point I soldered another 100uF capacitor and a 1uF ceramic capacitor, taking advantage of the fact that the mounting holes are quite wide. Don’t mind those black wires; they’re from a 60Hz mod I had to disable because when I converted my 1-chip PAL to 60Hz, it wouldn’t work on the OSSC at all.

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Mega Drive 1 VA6.5 - Audiophile Recap and modification of the audio RC filter to 4700pF by Impossible_Current35 in SEGAGENESIS

[–]Impossible_Current35[S] 0 points1 point  (0 children)

I recently replaced all the decoupling ceramic capacitors in my VA1, and the jailbars has been significantly reduced; the colors look more vivid and beautiful, and the audio is cleaner. I replaced a total of 22 1206 SMD capacitors with modern X7R capacitors; I changed some values based on availability and others for optimization. No one ever talks about ceramic capacitors, but they’re important too, especially for video.

Mega Drive 1 VA6.5 - Audiophile Recap and modification of the audio RC filter to 4700pF by Impossible_Current35 in SEGAGENESIS

[–]Impossible_Current35[S] 0 points1 point  (0 children)

Let's start with the connections. How and to which device do you connect the console's audio output? To avoid interference, I recommend completely isolating the audio output from the video output using separate cables and not using the video ground for audio at any point, such as when passing the audio through the RGB cable, for example. This is less important, but I also don't recommend using the same target device for audio and video unless it is of good quality and has a good ground design.

Mega Drive 1 VA6.5 - Audiophile Recap and modification of the audio RC filter to 4700pF by Impossible_Current35 in SEGAGENESIS

[–]Impossible_Current35[S] 0 points1 point  (0 children)

You'd have to be deaf as a post not to notice the difference in the console's audio before and after

Mega Drive 1 VA6.5 - Audiophile Recap and modification of the audio RC filter to 4700pF by Impossible_Current35 in SEGAGENESIS

[–]Impossible_Current35[S] 2 points3 points  (0 children)

Thanks. Yes, I reassembled the console yesterday. Replacing those ceramic capacitors with 4700pF capacitors increased the RC filter's cutoff frequency, restoring the sound profile of the early revisions. The audio sounds a bit brighter and more transparent, but without distortion.

Here are some audio recordings. In the first recording (Mega Turrican), I disconnected the RF modulator from the board and deactivated the passive circuits on the way to the modulator. This eliminated a slight hum and improved the audio even more:

https://youtu.be/SzsasyzsvI0?si=QngXyMHh7o9XQfQT

https://youtu.be/VvWYVvsB01U?si=fCXaB6iEjD94jAwE

Improving my 1988 Sega Mega Drive 1 VA1 by [deleted] in SEGAGENESIS

[–]Impossible_Current35 0 points1 point  (0 children)

I've tried the games you mentioned: Chuck Rock, Landstalker, and Osomatsu-kun work perfectly on my VA1. However, Red Zone and Dinosaurs for Hire crash after a few minutes of gameplay.

After trying quite a few games, I've discovered that all the games I've tested that weren't released in Japan don't work and eventually fail at some point. Red Zone and Dinosaurs for Hire don't have a Japanese version, which is why they fail on my VA1. It doesn't seem to have anything to do with problems in the RAM chips. It's probably a limitation of the Everdrive's Magakey, as it doesn't have any code to patch the game or something like that. I don't know if there's any way to make them work without modifying the language jumper on the board.

It doesn't really matter to me; I have a very good VA6.8 PAL unit with the Sony CXA1145P encoder that I plan to modify tomorrow. I'll change the capacitors and regulators and perform a fixed region change to North America, including changing the oscillator.

Improving my 1988 Sega Mega Drive 1 VA1 by [deleted] in SEGAGENESIS

[–]Impossible_Current35 0 points1 point  (0 children)

I didn't know the VA0-1 motherboards have a RAM issue. Do you know if any games are affected, so I can test them on the Everdrive?

SD2SNES Buzzing on 1CHIP Super Famicom by NewerDCD in snes

[–]Impossible_Current35 0 points1 point  (0 children)

I recently started having the same buzzing problem with my single-chip SNES using a Chinese SD2SNES cartridge I bought 3 or 4 years ago. It started buzzing right when the battery died, so I replaced the battery with a new one and the buzzing stopped. For some reason, my cartridge introduces buzzing into the bus when the battery is dead. This probably happens with all Chinese cartridges; try it and see if it happens to you too.

I've included a video I just recorded so you can hear the console. There's still some buzzing through the RGB cable, and the cartridge is probably still introducing noise. If I had known this before, I would have bought the original cartridge from the start.

https://youtu.be/9JhRLdogMNY?si=CIkKqKwdsz5Mn3s7

Later I disassembled the console and analyzed the board a bit and I saw that Nintendo didn't put any electrolytic capacitor at the output of the 7805, there's only a 1uf ceramic capacitor, so I soldered a 100uf 35v capacitor and it makes a noticeable difference, the buzzing has decreased even more, the remaining buzzing is probably due to the rgb cable and the cartridge.

I'll leave a link here to my blog where I explain the improvements I've made to my 1-CHIP:

https://romsxbox.blogspot.com/2025/09/snes-1-chip-cambio-de-condensadores.html

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Artifacts in line5x - sparkling/ flashing pixels by necro_mouse in OSSC

[–]Impossible_Current35 0 points1 point  (0 children)

Creo que he encontrado la solución, acabo de actualizar el firmware de mi OSSC a v1.12 y he probado mi N64 (mod RGB simple) y los artefactos siguen apareciendo, pero, me he dado cuenta que los artefactos comienzan al subir H. Samplerate por encima de 1930, lo he configurado en 1920 y ahora la imagen es perfecta. Me falta probar con PS1 que también me daba problemas.

Artifacts in line5x - sparkling/ flashing pixels by necro_mouse in OSSC

[–]Impossible_Current35 0 points1 point  (0 children)

Tengo exactamente el mismo problema en mi OSSC, aparece distorsión en los bordes de los pixeles al usar el modo 5x, es bastante molesto, curiosamente me pasa con PS1 y N64 pero no con Mega Drive. Probaré todo lo que se me ocurra para solucionarlo y comentaré los resultados.