So I had a go at performing this mod today. It does reduce the CLV smear. I've not spent time to see if there are other issues with it (the filter is probably there for a reason), but it works in my environment.
The smear effect is pretty subtle on my Sony PVM CRT and on my OLED calibrated Laserdisc settings. Using a non-calibrated profile (with higher brightness) shows the issue (and noise) more clearly, and is easier to to photograph.
First an image of the CLV smear from Star Wars opening sequence:
Attachment:
File comment: Original Output with CLV filter
Smear.jpeg [ 43.2 KiB | Viewed 1062 times ]
Same scene with bypass enabled (disabling CLV specific noise filtering):
Attachment:
File comment: Output with CLV filter bypass
NoSmear.jpeg [ 43.64 KiB | Viewed 1062 times ]
On to the mod details. Pin 50 of IC101 is XCLV, which passes through W497. I didn't want to remove the whole motherboard for testing the mod, so I cut W497 instead:
Attachment:
File comment: Pin 50 of IC101 is XCLV, which passes through W497.
W497 cut.jpeg [ 209.92 KiB | Viewed 1062 times ]
Wire these with a three pin, two way switch, to toggle between +5v and XCLV to the output;
Attachment:
File comment: Solder points for switch. +5v, XCLV from IC101, and output.
Switch Wiring Points.jpeg [ 221.95 KiB | Viewed 1062 times ]
I drilled a hole between the COAX and the Optical outputs, and mounted the switch on the rear.
Attachment:
File comment: Mounted switch interior.
Mounted Switch.jpeg [ 179.86 KiB | Viewed 1062 times ]
Overall, it's to early to tell whether this mod is worthwhile or not. The smearing is usually pretty subtle on my TV set, and the extra noise on CLV discs might make this mod pointless. Looking forward to finding out though!