SNES repairathon part 2: Simplified SHVC clock fix

[@113odyssey]

Very useful. Enjoying the series! Maybe a Megadrive series to follow?.. 🤔

[@TheRetroChannel]

Maybe 😉

[@coyote_den]

I think Mode 7 issues are going to be PPU1. PPU1 does all of the VRAM addressing, PPU2 does all of the layering and blending of the VRAM data. Mode 7 graphics are interleaved so that all map data is in one VRAM chip and all tile data is in the other chip. That arranges the data such that simple matrix math can be performed on the H/V counters, which is how it scales and rotates the screen. So, if the entire Mode 7 screen is scaled/rotated incorrectly but the actual map and tiles look OK, you can rule out VRAM and PPU2.

[@SweetBean92]

My money is on the CPU for the one that showed the broken mode 7 test. The broken menuing was actually my first hint.

[@Miguel_Sanchez69]

All hail to the lord himself Voultar! 🫡

[@snowgoer540]

This is a fantastic series!!

[@EvilCoopra]

As for the one board with the glitchy Mode7 - you can start with PPU2, but if I were you I would replace PPU1 first 😉

[@UpUpUpWithAFish]

Great video! I measured my North American SHVC SNES and saw Vamp of 1.9 using SD2SNES and 1.99 with an original cartridge (CPU/PPU1/PPU2 combination of 2/1/1). Any thoughts why my Vamp is so much lower than yours?

[@TheRetroChannel]

Are you measuring it from the same point - pin 31 of PPU2? 10x probe?

[@UpUpUpWithAFish]

@@TheRetroChannel Yes, pin 31 on PPU2 with a 10x/x1 probe set to x1. This is my first scope so I'm still learning and it's possible I'm doing something wrong. I tested a different SNES (GPM-02 with CPU/PPU1/PPU2 of 2/1/1) and it has Vamp of 2.86V with an original cartridge and 2.79V with the SD2SNES.

[@TheRetroChannel]

@UpUpUpWithAFish Definitely set your probe and scope to 10x. It's very rare you'll ever need to use 1x, and using 1x on a clock circuit will likely affect your readings

[@UpUpUpWithAFish]

@@TheRetroChannel AH, thank you! Setting the probe attenuation to 10x in the Rigol menu, as well as using 10x on the probe itself, gave a sane reading. Now the SHVC shows 3.42V Vamp with an original cartridge and 3.20V with the SD2SNES.

[@LaserFur]

I would leave R6 at least at least 33 ohms to prevent ringing.

[@watchmakerful]

Why is the stock clock signal a sine wave? It should be definitely passed through an amplifier or a Schmitt trigger. Digital circuitry usually does not tolerate intermediate levels between zero and the power source voltage.

[@TheRetroChannel]

It doesn't seem ideal, but that's how Nintendo did it and clearly it works.

[@LaserFur]

The design also tries to reduce RF emissions. The IC's used are also slow compared to the Clock rate. So the IC's are ok with it, but if the IC's using the clock are replaced with faster ones then the clock also has to have faster rise and fall times.

[@mundogamersguayaquil2524]

Disculpa tengo el mismo problema que la imagen va y viene o se queda bien y luego en negro la pantalla, ya cambie todo revise todo. Ahora veo sacas el capacitador y en la resistencia por cual capacidad reemplazas eso no entendi bien no se mucho ingles 😅 cual es el valor de la nueva resistencia?

[@TheRetroChannel]

0 ohms

[@mundogamersguayaquil2524]

@@TheRetroChannel okas ojalá pueda repararlo

[@mundogamersguayaquil2524]

Incluso el cartucho tester tambien me dice que todo esta correcto 😂😂 y luego da fallos de imagen 😢

[@willyarma_uk]

Works in all cases? but none of them were in cases! ;) Just Kidding. I am enjoying this series tho.

[@bblblp]

I accidentally locked in my like before the "stiff clock" joke. Oh well. j/k :)

[@rubberduck4966]

Removing components is no fixing its maybe workarounding.

[@shangrilai1990]

🍪

[@TheRetroChannel]

🔨🕑

[@guarapo66]

So, voultar clock mod and re-cap are the go to fixes for any snes at this point 📋

[@TheRetroChannel]

Recap for all, clock fix for the SHVC boards. And at least for me, digital audio mod and hopefully Voultar's edge enhancer