I would get to the PCB4 - mounted vertically, behind the display panel. There you will find a 3V lithium battery. I would unsolder that, leave it overnight, and then resolder it.
If you had to replace your laser 3 times on the CD5500, I would say that your service technician should go back to school - there are certain adjustments which have to be done after replacing the laser - spares are still available, and if you had been on this forum then, your CD5500 would probably still be giving you pleasure.
Sony lasers must never be adjusted after installation, but Philips lasers (in this CD5500) most definitely do require aadjustment.
Menahem
Learn from the mistakes of others - you'll not live long enough to make them all yourself!