Genesis:32X Buck Converter Mod
The 32X utilizes a buck converter topology based on the MC34064 (or similar) DC-DC converter IC to create the 5V rail used by the console. This is a much more efficient way to take a higher supply voltage — such as the 32X’s 10V input — and convert it to a lower voltage with greater than 80% efficiency. However, many 32X consoles suffer from a noisy coil that is likely caused by the converter going into discontinuous conduction mode, making the inductor to vibrate at an audible frequency.
Two fixes have been developed to address this issue:
- Changing the switching frequency on the existing converter and adding a feed forward resistor (least complexity, inductor still makes noise in light load conditions)
- A new converter design based on the NCP3063/NCV3063 DC-DC converter IC (best, slightly more complex, no audible noise in any load condition)
Timing/Feed-Forward Fix for Existing Regulator
The easiest fix to implement is replacing C85 with a 1 nF/1000 pF C0G/NP0 capacitor and connecting the positive side of C85/IC Pin 3 to the input voltage on R50 via an 86.6k leaded resistor. This supplies external charge current to the timing capacitor, C85, thereby reducing the duty cycle of the converter and causes the oscillator to operate at a higher frequency. The design frequency selected here was 100 kHz, but due to tolerances of components, it may be slightly higher or lower. The result is that the audible noise is eliminated in most gameplay situations, but persists on low load conditions, such as playing a Genesis game or idling in an Everdrive selection menu.
The NCP(V)3063 DC-DC converter was designed as an updated replacement for the MC34064 and its major improvements come in the form of added internal thermal shutoff and much higher switching frequency capability (up to 300 kHz). Utilizing the higher frequency, a new converter circuit has been designed by zaxour to be a mostly-drop in replacement, with the only additional component being a feed forward resistor. The target switching frequency of this circuit is 200 kHz, and no whine was observed in any load condition, after more than 24 hours of testing.
To implement this mod, the following components are required:
- 1x NCP3063 or NCV3063 SOIC-8 DC-DC Converter (replaces IC13)
- 1x 0.1 ohm size 2512 resistor (2W or greater, replaces R50)
- 1x 4.3 nF size 0603 C0G/NP0 ceramic capacitor (rated 25V or greater, replaces C85)
- 1x 11.8kOhm leaded resistor, 1/8W or greater
- 1x 100 uH leaded inductor, DC rated for 2A or greater (replaces L7)
Remove IC13, C85 and R50 and L7.
Replace the removed components, then solder the 11.8K resistor from IC13, pin 3 to R50, preferably the side closer to the DC power jack.