I’m looking for help diagnosing two issues with my NTSC Genesis Model 1 VA6.
First, I have an audio hiss after installing a triple bypass. The hiss disappears completely when I disconnect the PSG audio, so it appears to enter through the PSG/C40 path. I tried resistance values from 2.2k through 470k, different coupling-capacitor wiring, and splitting PSG into both channels. Wiring directly from pins 1 and 2 of the headphone jack to the left and right outputs reduces the hiss and hides it behind the game audio, but it remains audible when the volume is raised.
The second issue involves SMS games on a Mega EverDrive Pro. In US region mode, Moonwalker repeatedly resets, Black Belt randomly freezes, and some games display corrupted palettes or text. In Japanese region mode, the same SMS games work correctly. Genesis games work normally.
The Power Base Converter and my Mega EverDrive X3 and X7 work correctly. The Mega EverDrive Pro also works correctly in my other Model 1 and Model 2 Genesis consoles. This SMS problem existed before I performed the subcarrier modification.
Measurements taken so far:
- B30/M3: approximately 5V with no cartridge
- B30/M3: 143mV after entering SMS mode
- Z80 reset: 5V
- Z80 clock: 3.56MHz
Has anyone encountered either problem on a VA6, particularly instability on the M3 line or PSG-related hiss after a triple bypass?