PX-716A power cal and dvd read errors.
reloaded all software - no go.
removed eide cable powerup recal - no go.
tried compressed air with vacuum assist - no go.
removed case and vacuumed circuitry.
cleaned laser with alcohol 70% - no go.
removed laser cable from pcb power reset - no go.
edit- updated firmware to rev10, also using only verbatim 16x
dvd's.

then removed cable from laser, which was not installed
straight in the connector. examined with a magnifier and
noticed on one end that the trace had barely made contact
to the connector.
reinstalled cable flush with connector and unit working
like new.
Over a period of time the vibration from the movement
of the laser must have caused the connection to develope
a resistance. The unit would randomly work, but got worse
with time.
The connectors swing upward at a 90 degree angle to allow
the cable to be removed with zero force.
bwireman

Thanks for reporting.

It seems that the laser-pickup cable is one of the principal factors of drive failure. It can loose contact either by getting vibrated out of the connector over time or because of corrosion of the metal used. Apparently the problem is not unknown to drive manufacturers. On behalf of the Plextor Premium 2, Plextor has stated the following (mechanical translation from Japanese):

"The gold-plating was used for the connector part of the pickup and the flexible connector part of the baseplate as the needle-shaped monocrystal "ウィスカ" measure which recently, is thought the cause of causing trouble such as short circuit of the computer, occurs on membrane surface such as zinc, the correspondence which holds down occurrence of the "ウ ィ ス mosquito" to minimum was done."

So checking all cables (not only the laser-pickup one) in the drive might indeed be a solution to reviving a seemingly dead drive.

Followup:
All the verbatim 16x dvds that failed to burn after leadin, due to
the power calibration error, were good to burn movies.
So save your dvds, and try with another dvd burner if you
can not fix your existing burner.
Note: had saved my failed to burn dvds in a separate pack to be
discarded.
My unit after repair is still working like new, burned around 20 dvds.
bwireman

I think i had, in the past, reported something about that litle cable "IDE" conector not been well conected with the Laser...

Tks for the info!

Mordorr

i have now burned more than 120 dvd's without a coaster, since
reseating my cable into the laser assembly.
cables must not be skewed on any connectors, if you think
they are then remove and check with a magnifier on both side
of the cable for a similiar scratch pattern. you should see an l
centered on the gold trace on both sides of the cable where it
plugs into the connectors if the connection was good. it only
takes a small amount of skew to create a problem, though you
should be able to physically see the problem. by taking the time
to examine the cable you will know if you have indeed found
the source of your problems.

bwireman