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.