Playstation 2 V9 Failure answers and Facts ...
One of the latest V9 failure scenarios says that the PS2s fail because of poor manufacturing of the Laser Heads. Their problem is that their Focusing and Tracking coils have very small resistance (Partially shorted), so the chip (LA6) that drives them eventually burns!
The coils should be around 4 - 5 ohms!
In this pic that shows a V3 head you can see the points to measure each coil. The plastic cover should be removed to do this. Its generally not very easy to reach this point on a V9!!
Measuring the Coil Resistance
On the picture the terminals of the Tracking and the Focusing coils are shown with yellow (Focusing) and Red (Tracking) Dots!
Before installing a new chip on a V9 ps2 please measure the resistance with a multimeter (set at the minimum available scale) between the two red and the two yellow points.
The left dots are directly on the head and the right dots are the same but on the motherboard. To measure on the right ones, the head ribbon cable must be connected to the board.
The results are almost the same when the head is connected to the motherboard so its not necessary to remove the head!
MEASURING TIP: short the probes of your multimeter and note the indicated resistance (from 0,05 ohm for a Good Multimeter to 1 ohm for a poor one) and subtract this from the value you measure!!
Why Adding a Resistor between the LA and a coil will not avoid problems!
Its easy to think that a resistor would limit the current, protecting the LA6 but things do not work like this...
I am not exactly an artist, so this pic does not match the shape of the things in the PS2, but only how they supposed to work..
As you can see, there are the two poles of the Magnet (N and S) causing a field, and a coil that runs through the field (3 turns shown).
The coil is attached to the laser lens that needs to focus on the disc.
The springs that are also attached to the lens are keeping the head on its neutral position.
In order to focus, the LA gives a voltage at the edges of the coil causing current
(I=V/Rcoil).
The force that is produced by the coil is proportional to the number if the winding turns that are in the field and also proportional to the current that runs through the coil! This force that is produced is moving the lens until the Focus Control circuit says its in good position.
This keeps going on continuously as the disc anomalies require the Focus control circuit to tell the LA to increase- reduce or inverse the voltage so the lens is moved to a new position to focus correctly on the disc!
The problem about the LA6 chip lies here... In case of a bad coil that has low resistance, only one thing can be the reason for this. The coil is shorted! I believe its impossible for the constructor to have a short length of winding wire, so some (or many) windings are shorted!
In that case, in order to move the lens to the required position, the same Force has to be produced by the coil
F=n * I * X
(F=force, n= number of windings, I=current, X=several factors as the Field force the angle between the force and the coil, etc....).
So if the windings are shorted (reduced (n)), in order to achieve the same Force, we need more Current (I). More current means LA overheating and burning!
Now, if we add a RESISTOR between the coil and the LA, practically we change the current that flows through the coil by
I=V/(Rcoil + Rnew).
The current will flow through the coil will not be enough to produce enough Force to move the head to the required position, to the Focus Controller will tell the LA to give more Voltage to provoke more current enough to do the job!! So with a small Resistor , NOTHING changes!!
The only way to actually protect the LA6 is to put a Resistor so big, that the Max LA6 Voltage will not suffice to cause enough current to burn the chip. BUT in this case the lens will not be able to move to the position required to Focus! The head will loose focus, so no Disc reading!
You can say "better not be able to read discs with anomalies than burn!!".
True, but in most cases a single peak to keep the focus is required on an OK disc and it will not burn the PS2. With a resistor this Big, this will not be possible!
The same stand for the Tracking Coil too!
Why failures happen when we install chip??
If the coil's resistance is rediculusly small (VERY shorted!) the PS will inevitably fail either way!
If the coil is slightly shorted (i.e. 3 instead of the nominal 4,5 ohm), reading quality Original discs will make very few extreme focus and tracking corrections and the higher than normal current will not be enough to burn the LA6! When we install a Modchip, nothing changes on the Board's Circuit!!! The only thing that changes is the quality of the MEDIA. Copies require much more frequent and extreme corrections to read the discs and the PS2 cant stand the pressure with a bad coil!!
