I have tried one of the 400Q lasers and it does OK for me, but not as good as an original 400C.
As far as adjusting them goes, the resistance measurements on potentiometers should never be used as an absolute guideline for adjusting a laser (this is based on what I learned YEARS ago as an electronics tech, I have been out of it for a long time so I may not be able to explain it correctly).
Think about it like this; each component in any given circuit has a tolerance value. They can be 1% (very rare), 5%, or sometimes 10% (this is a generalization - there are other tolerances available). This holds true for potentiometers as well. What this means is that on one device you may have to adjust a pot to say 1000 ohms to get the rated output (whatever that may be - say 1.5 milliwatts). On another device of identical construction you may have to adjust the potentiometer to 900 ohms to get the same output from the laser. Both parts would function fine even though the resistance that the pots are set to are different.
Back in the early 90s when I used to repair CD players no one really knew or cared what resistance value the adjustment pot was set to. The manufacturer of the product would have an output rating for that laser diode. We would then use a laser power meter to measure the output and adjust it accordingly. No matter what else you do if the output is too high or too low you will have problems.
I have seen the oscilloscope method of adjustment mentioned before regarding PS2 adjustments and this would come very close to achieving the same results. Unfortunately from what I have heard Sony keeps that adjustment procedure under lock and key for obvious reasons. I used to know someone that had access to that information and was under strict orders to never let it go public.
So I guess the best adjustment procedure may be taking a measurement from a known good laser using a power meter and then trying to duplicate it on the replacement part. I don't know how easy this would be on a PS2 since it has TWO laser emitters instead of one, but I think I have read somewhere that this is still the preferred method.
If anyone has any more info to add please tag it on. I would love to get some oscilloscope measuring procedures for the V7-V10 models since I do have a personal oscilloscope but do not own a laser power meter. The only problem with this method is that it works best with a disk specifically set up for this process (a "test disk" so to speak).
Keep the info coming! I much prefer an older PS2 with a hard drive mounted in it myself over the newer models.
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