How the Playstation 2 LA6 and BA58 Chips Behave with different Media types

@PS_2

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Playstation 2 tutorials

· 3 years ago

TASK

To understand how different DVD media types affect the focusing coils and the LA6/BA58 chips in the context of the v9 "snuffed" PS2 question. It is not in doubt that a noticeable number of v9 PS2s are suffering failure of the LA6 chip.

PHYSICALS

The resistance across the focusing coils was measured at 5 ohms
The voltage swing was measured at best case 1v worst case 8v
The BA5815FM specification offers absolute maximum power dissipation of 2.2W at 25°C. This is assumed to be true also of the LA6 chip (no spec available)

If current I = V/R and power W = V*I, then W= (V^2)/R. 2.2W is reached @ R= 5 ohms when V = 3.32 at 25°C ambient temperature or less

However, the temperature inside the PS2 at the BA/LA location could easily reach 60°C (the fan does not blow into that area) and what is known as a Derating Curve applies as the ambient temperature rises.

As a generalisation, if the temperature at the BA/LA chip rises to, say, 60°C, then its maximum power dissipation value falls to around 1.2W.

If W= (V^2)/R then 1.2W is reached @ R= 5 ohms when V = 2.45 at 60°C ambient temperature. In these circumstances, the BA/LA chips tolerances will be exceeded.

The duty cycle on a continuous basis should be regarded as 50% since the voltage is applied on a swing basis as the PS2 tries to maintain focus. This will have the effect for the purpose of this explanation of regarding the measured voltage as equivalent to HALF when calculating power dissipation.

LA6 vs BA58

There is no published specification of the LA6 driver so it is assumed that the thermal specification will be similar to that of the BA58.

The pins are different. For example the FOCUS drivers are on pins 15 & 16 on the BA58; however they are on pins 18 & 19 on the LA6 (as metered to the disk ribbon connector).

OVERVIEW OF TESTS PERFORMED ON SCPH 50004/BIOS 110

The PS2 was fully assembled except that the top plastic case cover was removed and the disk drive was played with an open top so that activity could be observed.
The LA chip did NOT have a thermal transfer pad. One was duly fitted (and to the LB chip).
Two wires were brought out of the PS2 connected to pins 18 & 19 of the LA chip; these wires were then connected to a calibrated oscilloscope. Voltages were measured.
The following media were used for the tests:

---------- DVD Game PAL original
---------- DVD9 Game NTSC-J original
---------- DVD9 Game NTSC-J Silver
---------- DVD-R Ritek PAL
---------- DVD-R Princo PAL (working)
---------- DVD-R Princo PAL (dodgy)
---------- DVD-R Memorex (working)
---------- DVD-R White Label (working)
---------- TRAXDATA DVD-R Movie
---------- AUDIO CD

Observations were made of voltages and focusing sounds during booting, loading and early game play.

FINDINGS

Please read this section in conjunction with the jpg image.

SWITCH ON PS2 - RESET SWITCH

The sled moves to the centre of the disk and immediately on hitting the limit switch, the laser comes on and the lens moves up and down twice to find the groove (once in red, once in infra-red).

There's a 4v swing when that happens. It's a very large movement if there is no disk in the tray.

DVD GAME PAL ORIGINAL

This corresponds with the first graphing illustration

This showed a constant voltage in the +½ to -½ volt swing range - a total swing of 1v. Reasonably stable with spikes only when the sled moves and it needs to hold focus. This provided the reference basis.

Using general power derating tables and 50% duty cycle, W = ((1/2)^2)/5 = 0.05W which would be the maximum dissipation power at an ambient temperature of c. 80°C.

DVD9 GAME NTSC-J ORIGINAL

This corresponds with the second graphing illustration

This showed a constant voltage in the range +¾ to -¾ volt swing range, a total swing of 1½v, otherwise behaving as per DVD game original.

Using general power derating tables and 50% duty cycle, W = ((1½/2)^2)/5 = 0.11W which would be the maximum dissipation power at an ambient temperature of c. 78°C.

DVD9 GAME NTSC-J SILVER

This corresponds with the third graphing illustration

This showed a constant voltage in the range +¾ to -¾ volt swing range, a total swing of 1½v, otherwise behaving as per DVD game original.

Using general power derating tables and 50% duty cycle, W = ((1½/2)^2)/5 = 0.11W which would be the maximum dissipation power at an ambient temperature of c. 78°C.

DVD-R GAME RITEK PAL
DVD-R GAME MEMOREX PAL

This corresponds with the fourth graphing illustration

This showed a constant voltage in the range +½ to -½ volt swing range, a total swing of 1v, but showing regular spikes to +1v and -1v, say every second or so. Otherwise behaving as per DVD game original.

DVD-R GAME PRINCO PAL (WORKING)

This corresponds with the fifth graphing illustration

This showed a constant voltage in the range +¾ to -¾ volt swing range, a total swing of 1½v. The spikes between +1v and -1v were twice as frequent as for Ritek disks. When the sled moved and focus had to follow, there were large sustained voltage swings of 4v.

Taking those sustained swings of 4v and using general power derating tables and 50% duty cycle, W = ((4/2)^2)/5 = 0.8 which would be the maximum dissipation power at an ambient temperature of c. 65°C. BORDERING ON THE WORRISOME.

DVD-R GAME PRINCO PAL (SUSPECT)

This corresponds with the sixth graphing illustration

This disk had serious focusing problems. Whilst struggling, it showed a sustained voltage in the range +4 to -4 volt swing range, a total swing of 8v, lasting for about a second and then immediately again until it found focus.

Taking those sustained swings of 8v and using general power derating tables and 50% duty cycle, W = ((8/2)^2)/5 = 3.2W which EXCEEDS the maximum dissipation power at any ambient temperature.

DVD-R GAME WHITE LABEL PAL (WORKING)

There is no graphing illustration

This showed a constant voltage in the range +¾ to -¾ volt swing range, a total swing of 1½v. The spikes between +3v and -3v were as frequent as for Princo disks. When the sled moved and focus had to follow, there were large sustained voltage swings of 6v.

Taking those sustained swings of 6v and using general power derating tables and 50% duty cycle, W = ((6/2)^2)/5 = 1.8 which would be the maximum dissipation power at an ambient temperature of c. 50°C. HEAT TRANSFER IS MOST NECESSARY HERE.

DVD-R MOVIE TRAXDATA

This corresponds with the seventh graphing illustration

This showed a constant voltage in the +½ to -½ volt swing range - a total swing of 1v. Reasonably stable but with a regular cyclic pulse to give a 2v swing. Either the disk wasn't flat (looked flat to me) and I got the impression that a DVD-R movie would nake the LA chip work quite hard.

Taking the swings of 2v and using general power derating tables and 50% duty cycle, W = ((2/2)^2)/5 = 0.2 which would be the maximum dissipation power at an ambient temperature of c. 76°C.

CD AUDIO

There is no graphing illustration

This showed very little voltage around the zero point. Stable and low power consumption.

CONCLUSIONS

It is assumed that the temperature inside the PS2 in the vicinity of the LA chip well exceeds 25°C - probably in the 60°C zone. This has not been proved - however, a heat sink will dissipate the heat adequately.
In the absence of a heatsink, and assuming an ambient temperature of c. 60°C, then any disk that causes a sustained voltage of 6v or more to occur, threatens the power dissipation limits of the LA chip.
Thus the following media judged by these tests would be safe to used under the above assumptions: