Fault-finding in a Sony SCD-XA9000ES

[Triophile]

I'm just wondering if someone can help me home in on the likely cause of this player's erratic reading of discs, mainly CDs and hybrid SACD discs.

I got this nice and cheap through a mag ad, knowing full well it was very temperamental. Basically, it's worth a crack at for what I paid...

A number of years ago, this player (vintage 2004, I believe) started having problems reading and playing some discs. This worsened, until a local shop attempted a repair by disassembling, checking, and re-assembling the disc clamping mechanism. Maybe they were checking if the disc table was at the right height... Whatever the reason, that failed to fix the problem.

Apparently, the fitting in mid-2009 of a new optical block and replacement of IC901 (listed in the service manual only as 'CPU') fixed the problem, until one particular disc caused garbled characters to appear on the Sony's display, since which time the seller believes the reading problems began to return (though there has been no repeat of the garbled characters on the player's display).

In classic fashion, the player has now reached a point where it is very fussy, often claiming there's no disc in the mech if it's a CD or hybrid SACD. The spindle motor can be heard whirring up to speed and then back down, and the tracking motor searching around for something the head can recognise. The player seemed to read the TOC and then play the seller's few pure SACDs OK.

I've not had a chance to test it properly myself, having only just got back from collecting it, but I had assumed (before the garbled display was mentioned) that it might be some sort of problem with lens contamination (though from a non-smoking home) or mech misalignment. Could it also be a supply rail problem? Given the fact that the optical block is only about a year old, I'm hoping to get the player sorted without having to splash too much on expensive spares.

Cheers, Jon.