LaserActive:PAC-S10 Audio Circuit Service Bulletin Update
According to a service bulletin from Pioneer, early revisions of the PAC-S10 and S1 needed adjustments to the audio circuit to avoid distorting high frequency audio "when a certain Sega game software is played." However, this distorted audio affects all games and it is recommended to perform the resistor/capacitor replacements.
MDFourier Plots
Prior to the service bulletin update, MDFourier analysis reveals that the audio signature of the PAC-S10 is quite distorted across the frequency range, with extreme clipping occurring on the PCM, CD-DA and PSG channels. FM audio begins to distort around 500 Hz. After applying the service bulletin update, the frequency response is much more even across the band, despite the Genesis audio portion rolling off around 7-8 kHz and CD-related audio around 10 kHz.
NOTE: When performing MDFourier analysis on the Laseractive, the PAC-S10/S1 internal oscillator runs at a slightly higher frequency than the original Genesis hardware. The -R and -T options were used for this analysis.
MDFourier Spectral Plot, Pre-Bulletin
MDFourier Spectral Plot, Post-Bulletin
Installation
You will need the following parts for this modification:
- 33K 0805 1/10W+ Resistor (Qty 4)
- 100K 0805 1/10W+ Resistor (Qty 2)
- 27K 0805 1/10W+ Resistor (Qty 2)
- 22K 0805 1/10W+ Resistor (Qty 2)
- 3.3K 0805 1/10W+ Resistor (Qty 2)
- 120pF 0805 25V+ Capacitor (Qty 2)
- 820pF 0805 25V+ Capacitor (Qty 2)
Note: The bulletin also indicates that the large surface mount electrolytic AC coupling caps (C117 and C21) are to be replaced with 1 uF, 50V rated caps. This is not required, but recommended.
Replace the parts indicated as directed in the list below:
Service Bulletin Audio Circuit Schematic
Parts to be replaced, highlighted
Using the parts listed above, replace the parts as indicated:
- R31, R58, R32, R59 - 33K
- R33, R34 - 100K
- R131, R42 - 27K
- R38, R40 - 22K
- R39, R41 - 3.3K
- C16, C17 - 120pF
- C33, C34 - 820 pF