Editing CD drive

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Supports speeds of 1x and 2x and can switch between them.
Supports speeds of 1x and 2x and can switch between them.


The tracking-servo (balance and gain) is self-adjusting on all consoles, while the focus-servo needs potentiometer-adjustments (bias and gain) on earlier consoles.
From PU-18 and up, focus gain and bias are auto-adjusted at disc-spinup, which creates an audible "beep" coming from the optical pickup's coils during auto adjustment.
From PU-18 and up, both the focus and tracking servos are self-adjusting at disc-spinup, which creates an audible "beep" coming from the optical pickup's coils during auto adjustment.


== Electronics ==
== Electronics ==
The CD subsystem of a first generation [[Motherboards#PU-7|PU-7]]-based PlayStation consists of the following hardware components:
The CD subsystem of a first generation [[Motherboards#PU-7|PU-7]]-based PlayStation consists of the following hardware components:


* BA6398FP: [[CD Driver|BTL-driver]] (for electrically driving the motors)
* [[Sub_CPU|Sub-CPU/Mecha-Con]]
* CXD1199BQ: [[CD controller]] (with 32 KB of external RAM)
* CXD2516Q: [[CD DSP]]
* CXA1782BR: [[Servo controller]] + [[RF-amp]]
* CXA1782BR: [[Servo controller]] + [[RF-amp]]
* CXD2516Q: [[CD DSP]]
* BA6398FP: [[CD Driver]]
* CXD1199BQ: [[CD decoder]] (with 32 KB of external RAM)
* [[Sub_CPU|Sub-CPU/Mecha-Con]]


Over the years, these components have been consolidated into fewer, more complex ICs.
Over the years, these components have been consolidated into fewer, more complex ICs.
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** Compatible with PU-7, PU-8 and PU-16 boards  
** Compatible with PU-7, PU-8 and PU-16 boards  
** Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
** Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
** Has issues with premature mechanical wear due to the laser block gliding on a plastic peg rather than metal/nylon
** Has issues with premature mechanical wear due to the laser block gliding on a plastic peg rather than metal
* KSM-440ABM
* KSM-440ABM
** Compatible with PU-7, PU-8 and PU-16 boards  
** Compatible with PU-7, PU-8 and PU-16 boards  
** Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
** Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
** Has issues with premature mechanical wear due to the laser block gliding on a plastic peg rather than metal/nylon
** Has issues with premature mechanical wear due to the laser block gliding on a plastic peg rather than metal
* KSM-440ACM
* KSM-440ACM
** Compatible with PU-7, PU-8 and PU-16 boards  
** Compatible with PU-7, PU-8 and PU-16 boards  
** Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
** Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
** Early revisions of KSM-440ACM have issues with premature mechanical wear due to the laser block gliding on a plastic peg rather than metal/nylon; later ones have the laser block made of cast metal as well as a gliding element made of nylon, as do all the later drives
** Early revisions of KSM-440ACM have issues with premature mechanical wear due to the laser block gliding on a plastic peg rather than metal; later ones have the laser block made of cast metal as do the later drives
* KSM-440ADM
* KSM-440ADM
** Compatible with PU-18 and PU-20 boards
** Compatible with PU-18 and PU-20 boards
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{| class="wikitable" style="text-align:center; margin: 1em auto 1em auto;"
{| class="wikitable" style="text-align:center; margin: 1em auto 1em auto;"
|+ Motherboard/CD-Drive mechanical compatibility
|+ Motherboard/CD-Drive compatibility
|-
|-
!rowspan="1"|compatible
!rowspan="1"|compatible
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|{{Yes}}
|{{Yes}}
|}
|}
[[File:PlayStation Pickup.jpg|thumb|center|Comparison between KSM-440AAM (which does have the wear/FMV stuttering issues) and KSM-440ACM (which mitigates these issues)]]


== Copy protection + Region locking ==
== Copy protection + Region locking ==
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The PlayStation exploits this inherent feature of the CD format by having a specially crafted wobbly groove at the beginning of each original disc. The console now monitors the tracking movements the laser has to do to follow this groove and extracts a signal out of this. After this, a string can be extracted from that signal. This string is either SCEI (for Japan and Asia discs), SCEA (for North America discs) or SCEE (for all PAL region discs). The console then compares this to a string it expects, which differs depending on the region of the console. Hence, this method combines both, copy protection and region locking.
The PlayStation exploits this inherent feature of the CD format by having a specially crafted wobbly groove at the beginning of each original disc. The console now monitors the tracking movements the laser has to do to follow this groove and extracts a signal out of this. After this, a string can be extracted from that signal. This string is either SCEI (for Japan and Asia discs), SCEA (for North America discs) or SCEE (for all PAL region discs). The console then compares this to a string it expects, which differs depending on the region of the console. Hence, this method combines both, copy protection and region locking.


The exact way this signal is being extracted by the drive electronics and how it's compared differs between [[Motherboards|motherboard revisions]]. E.g. PU-7, PU-8 and PU-16 have the circuit built from discrete op-amps and passive components, PU-18 and PU-20 use a semi-custom analog IC, and PU-22 and all later boards do all of this inside the DSP/CD-ROM decoder/SPU combo IC.
The exact way this signal is being extracted by the drive electronics and how it's compared differs between [[Motherboards|motherboard revisions]]. E.g. PU-7, PU-8 and PU-16 have the circuit built from discrete op-amps and passive components, PU-18 and PU-20 use a semi-custom analog IC, and PU-22 and all later boards do all of this inside the DSP/CD-ROM controller/SPU combo IC.


The extraction circuit requires electric adjustment using a potentiometer on PU-8, PU-16, PU-18 and PU-20 to properly function. Later boards don't require adjustment. The potentiometer setting is called "Push-Pull" in official documentation and - on some board revisions - also labeled as such on the board. On PU-8 and PU-16, the potentiometer is RV702. On PU-18 and PU-20, it's RV703 (which is the only potentiometer on these boards). Proper adjustment requires an oscilloscope, a special test disc (SCD-2700) and a way of turning off the tracking servo (could likely been done through software on the test disc). Rough adjustment can be done using an oscilloscope and a standard audio CD (originals only, no burnt discs) only and is more than enough to get the drive into a reliable state.
The extraction circuit requires electric adjustment using a potentiometer on PU-8, PU-16, PU-18 and PU-20 to properly function. Later boards don't require adjustment. The potentiometer setting is called "Push-Pull" in official documentation and - on some board revisions - also labeled as such on the board. On PU-8 and PU-16, the potentiometer is RV702. On PU-18 and PU-20, it's RV703 (which is the only potentiometer on these boards). Proper adjustment requires an oscilloscope, a special test disc (SCD-2700) and a way of turning off the tracking servo (could likely been done through software on the test disc). Rough adjustment can be done using an oscilloscope and a standard audio CD (originals only, no burnt discs) only and is more than enough to get the drive into a reliable state.
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=== Electrical ===
=== Electrical ===
== Laser unit ==
The PlayStation drive's pickup employs a "Laser Coupler", which is a single unit consisting of a Laser Diode (LD), Photo Diode (PD, for monitoring the laser output power) and Photo Detector IC (PDIC, the actual laser signal detector).<br/>
[[File:PS1 laser coupler.jpg|240px]]


== Adjustments ==
== Adjustments ==
=== Potentiometers ===
=== Potentiometers ===
==== All consoles ====
==== All consoles ====
* ''All consoles have a '''potentiometer on the disc drive's laser flex cable'''. This potentiometer adjusts the output of the power monitoring photo diode for the APC (automatic power control) circuit. This setting is done exactly once in the factory using a laser power meter in a special jig that the drive unit is placed in outside the console. '''It is not meant to be changed ever again when servicing a console. It does NOT directly control laser power, which is instead done by the APC circuit.''' The APC circuit will automatically compensate for aging/weak lasers, keeping the output power constant. Turning this potentiometer will actually increase output power beyond specification. The only reason this sometimes resolves disc reading issues is because it increases the drive's tolerance to other factors like dirt inside the lens assembly or on the laser IC, skewed laser sled (due to mechanical wear) etc. It does NOT fix the actual issue. '''Hence, this setting should ONLY be changed as a last resort''', if everything else fails, and in that case, replacement of the optical pickup WILL be required at a later point.''
* ''All consoles have a '''potentiometer on the disc drive's laser flex cable'''. This potentiometer adjusts the output of the power monitoring photo diode for the APC (automatic power control) circuit. This setting is done exactly once in the factory using a laser power meter in a special jig thayt the drive unit is placed in outside the console. '''It is not meant to be changed ever again when servicing a console. It does NOT directly control laser power, which is instead done by the APC circuit.''' The APC circuit will automatically compensate for aging/weak lasers, keeping the output power constant. Turning this potentiometer will actually increase output power beyond specification. The only reason this sometimes resolves disc reading issues is because it increases the drive's tolerance to other factors like dirt inside the lens assembly or on the laser IC, skewed laser sled (due to mechanical wear) etc. It does NOT fix the actual issue. '''Hence, this setting should ONLY be changed as a last resort''', if everything else fails, and in that case, replacement of the optical pickup WILL be required at a later point.''
* ''Some revisions of the power supply have a potentiometer to fine-adjust the output voltage. Normally, changing this should not be necessary, unless repair work has been done to the power supply. Adjustment is done using a multimeter and setting the 3.5V output to exactly 3.5V, measured on the power supply itself with the console turned on. This will also affect the 8V output, which however does have a far larger tolerance, since it will get converted to a stable 5V on the motherboard through a linear voltage regulator which supports a range of input voltages. The other use of the 8V output is for the [[CD Driver|BTL-driver]] and the wobble-extraction circuit, so on boards up to including PU-20, especially on PU-7 to PU-16, recalibrating the drive electronics could be necessary if reading issues arise after changing the power supply output voltage.''
* ''Some revisions of the power supply have a potentiometer to fine-adjust the output voltage. Normally, changing this should not be necessary, unless repair work has been done to the power supply. Adjustment is done using a multimeter and setting the 3.5V output to exactly 3.5V, measured on the power supply itself with the console turned on. This will also affect the 8V output, which however does have a far larger tolerance, since it will get converted to a stable 5V on the motherboard through a linear voltage regulator which supports a range of input voltages. The other use of the 8V output is for the [[CD Driver|BTL-driver]] and the wobble-extraction circuit, so on boards up to including PU-20, especially on PU-7 to PU-16, recalibrating the drive electronics could be necessary if reading issues arise after changing the power supply output voltage.''


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