Possible Supercheap Blu Ray Repair / Diode Replacement Options

[relaxxx]

I'm considering trying a real cheap dirty fix, just for the hell of it...

I have a bunch of KES-400A lasers with bad diodes and I think it might be possible to get them reading without shelling out $40-50 for new ones. When I mean cheap, I mean $2.80 cheap! I can get a 20mA 405nm china laser for as little as $2.80 shipped! From what I see there are two potential problems and one obvious one....

Obviously with this, it will only read Blu Ray disks as ther is no red or IR diode combined. I don't really care about that problem.

First real problem; voltage difference; I hear the KES diode runs at 4.5V? not sure exactly but the cheapo diodes I'm looking at operate at 2.2V, also they might not be "clean' or high quality enough to use as a reading laser. I guess that's another potential problem. So unless someone can tell me exact specs I'll have to guess and reduce the voltage 2 volts or so, easy enough with a resistor and diode.

Second real potential problem; Is the "PD" signal needed (Photodiode Anode Monitor)? What does this do, will the sled IC operate without it connected? Do I need to simulate a signal (1V, 2V, 4.5V...) on this pin line? The cheapo diodes do not have this pin. Hold on, maybe they do, hmmm, there is 3 pins but the simple schematic image just shows NC for the center pin? I think the PD signal might be needed for the IC to regulate the diode current or something. Does anyone know exactly what this pin does? thanks.

[relaxxx]

Did some more testing: I found a 3 pin BD diode from another bad drive, tested and was emitting light so I connected it to the KESD-400A. I only wired two wires, the ground and VLD pins. I did not solder the PD signal to anything. Installed the laser assembly back in the drive and loaded it up, blu ray laser lights up and spins disk for a while but it stops after a few seconds. No joy

The spinning is a sign of hope tho, before swapping diodes this laser did not even attempt to spin the disk at all.

Next I might try connecting the VLD contact directly to the PD but I'd like to find out more about this signal first before so I don't fry the laser IC.

[relaxxx]

If anyone's interested, I tried the PD signal connected in line with the VLD power and it didn't light up at all.

Luckily it seems it did no damage because as soon as I disconnect PD the laser lights back up and spins the disk.

So what I think is going on is that the laser only reads the disk at a certain threshold or intensity range that I'm probably exceeding. I guess the only thing left is to experiment with different resistors to get the laser brightness just right.