Adjusting and Calibrating your Laser

[Administrator]

In order to adjust your PSX laser, you will need an oscilloscope. Preferably, an analog one. The digital ones just don't cut it. For the calibration test, make sure you use an original/official PlayStation 1 game. Just load it up and let the game run as normal.

Now, find the test point labeled "CL701". This is the RF eye pattern test point.
It is usually near the servo circuitry.


This is the test point on a SCPH-7000 board.


What you're looking for is a voltage ranged from 0.90mV to 1.35V.
Mind you that if you have a modchip and you load a copied CD-R, the voltage will appear lower than when you tested with an official PlayStation format CD-ROM (IE: a pressed disc which is an entirely differently method of signal interpretation from a dye based disc).

You can see here, it is a little low.


After turning the pot on the ribbon cable on the sled mechanism itself, it started to increase in power.


There are further tests which need to be done as well from other test points on the mainboard, but we won't go into those here since they are a bit more involved. The voltage adjustment to get the correct RF eye pattern will suffice enough to get discs to read correctly. It is also important to ensure that your CD-ROM mechanism (IE: the sled) isn't worn out since the plastic they are made from tends to degrade and eat the material away by abrasive measures.

[djstkg]

Hi Shadow,

Could you give us a complete specification? I need RV703 in my SCPH-5502.

[Administrator]

Hi Shadow,

Could you give us a complete specification? I need RV703 in my SCPH-5502.

There's a service manual for the 5502. If you don't know where it is, just probe with your scope until you come across the eye pattern on the test points near the CD-ROM ribbon header on the mainboard.

Just be careful when doing this work because the power supply is exposed with live voltage. Take the correct precautions (probe with 1 hand (or better yet just solder test leads), wear rubber shoes, make sure your AC power is protected with an RCD, etc).

[djstkg]

Hi Shadow,

Thanks for quick response.

Is it possible to get the service manual?

P.S. The thing is that my CD doesn't get read. It starts spinning, the laser head goes up and down x2 bit then the CD stops. So I am trying with adjustments now, before I rule out the CD reader as dead.

Hi Shadow,

Could you give us a complete specification? I need RV703 in my SCPH-5502.

There's a service manual for the 5502. If you don't know where it is, just probe with your scope until you come across the eye pattern on the test points near the CD-ROM ribbon header on the mainboard.

Just be careful when doing this work because the power supply is exposed with live voltage. Take the correct precautions (probe with 1 hand (or better yet just solder test leads), wear rubber shoes, make sure your AC power is protected with an RCD, etc).

[djstkg]

As said in my other post got the service manual from here:

https://www.jonathandupre.fr/articles/1 ... -scph-1002

[Jackhead]

i have some trouble calibrate my Laser unit. First i have a scope to see the eye pattern. And its also clear how to adjust it.
My problem is follow: When i finish with the adjust, drive reading discs fine no stuttering. Than i power off my PS1 and 10sec later when i turn it on again the drive spins up and nothing. I checked than the Gain again and i see the value wents up for around 0.02v. So i have to adjust the gain again and its working fine till the next coldboot.
Bias and drive voltage dont change. Only the Gain.
Why???
My first thinking goes that the poti has some problems, but i dont know.
Maybe a bad Laser unit?
Any idea?