On Wednesday, May 31, 2017 at 8:30:01 AM UTC-4, Miguel Giménez wrote:
Hi

In the last years I have changed twice the laser unit of my Aiwa CD
reader and once the unit of my mom's Sony reader. The three were
original spare parts, and the three died months after.

Why this happen? Do I need to adjust laser current after change? Are
they basically unreliable?

TIA

--
Regards
Miguel Giménez

Don't know about your particular drives, but anybody who did any kind of audio work in the 90s knows that Sony lasers were/are pure, unadulterated ****. I'm being kind here.

There were tons of otherwise very nice Aiwa three CD carousel combo stereos that had decent power and respectable sound (given the market) and enough LEDs flashing to keep the Walmart buyers enthralled. Unfortunately, they all came equipped with Sony lasers. We pulled the plug on doing these after the first few failed and recommended that our customers use these for "garage" radios.

Now I've heard that there were/are Chinese counterfeits for these and this might explain repeat failures, but it doesn't explain why so many Aiwa and Sony brand CD players came in for weak or dead lasers in two years.