Laser calibration using an oscilloscope  

Most laser calibration guides, like the previous one, for the PS2 are all about adjusting the laser potentiometers "blindly" or using a multimeter to measure the resistance of the potentiometers.

However, the reason you use variable potentiometers is that every PS2 need individual adjustment, so you cannot just use one reference value. What you need is an oscilloscope and/or a laser power meter to measure what is going on when you turn the pots. It is always best to measure on a brand new well working PS2 to get some reference values to use when you are calibrating a bad laser.  

If you have a laser power meter, you just have to put the photo-detector directly above the laser lens and look at the readout. If you are using an oscilloscope, you have to know where to find the RF/Eye Pattern measure points. 

Laser potentiometers on the PS2 locations are as follows:

This is a picture from the underside of the PS2 Laser. The pots are marked on the picture. Turn clockwise to increase power and counter clockwise to decrease power.

Do not turn these wildly, or you might kill your laser by using too much power, or just be unable to get back to a working setting.

Now, get your scope and connect it to the proper test point. You also need to find a good ground connection, if you do not know how you should not be reading this any further.

Even if we have not scanned your exact PS2 model, you should be able to find the test point as your board is probably very similar to one of the following pictures:

 -          Japan PS2 SCPH-10000

-         Euro PS2 SCPH-30004 "v3"

-         Euro PS2 SCPH-30004 "v4"

-         Euro PS2 SCPH-30004R "v5"

Adjust your oscilloscope and start measuring on the signal point for your board.

Set the scope at 20mV and 0.2us Sweep. The scope must be at least 20Mhz.

 When you connect the scope, you should se a clear "eye pattern" signal, like the one above.

 When you increase laser power, the amplitude (height) of the pattern will increase. Do not adjust too high, or the pattern will "clip" at the top and bottom.

 You will have to test with several different discs/media as all media have different reflectivity. Therefore, if you calibrate the laser so it will be just below clipping with cd-r media, it might "clip" when using originals.

 We recommend you take readings from a brand new PS2 to get reference levels. Normal values are 800mV peak to peak with DVD media and 640mV peak to peak with CD media. 

Clipped signal at the top and bottom of the pattern.