To Quaddy,
I just traced the power input from the AC connector and switch to the power supply input. Since then, I have found there are a few variations of the power supply board, so it might vary from unit to unit even though the model number (e.g., SCPH-100X, SCPH-550X, etc.) may be the same. I recommend using a meter to check continuity. To be honest, I haven't tried reversing the Isoclean fuse to hear any difference. All I know is that installing the fuse made a noticeable improvement in low end definition, further reducing background noise (very negligible to begin with) and dynamic response. I believe HiFi Tuning and other alternative fuses are "non-directional," so this may be a moot issue.
To Souterncross,
I plan to separate the power supply also and re-case everything. I'll replace some of the caps on the power supply and install a Furutech IEC inlet to allow use of a standard 3-prong IEC plug. For a DC power cable between the power supply and main unit, I'll use a high quality 5-pin DIN connector cable (a la Naim power supplies). I am also planning to fabricate a quality wooden cabinet for the main unit. The power supply will go into an extruded Aluminum project box to minimize RFI. I also plan to use higher quality Vampire RCA ouput jacks for the stereo output. I am very happy with the Black Gate N 4.7uF and 22k PRP metal oxide resistors for the simple output stage. The sound is very clear, detailed, extended and organic. Anyone who has modded a Playstation 1 has found out just how good the Playstation can be for Red Book CD playback. I don't think I could ever go back to a stock unit again.