flash sony dru-510a back to dw-u14a?

hi, i got a sony dw-u14a (OEM version of 510a) and it was faulty so i was advided to flash it to the sony dru-51a, which i did, but to no avail.
now i want to return it to the vendor, but think i need to get it back to the dw-u14a firmware version before i do so.. is this possible, how can i do it?
any help is great
cheers....

p.s.. oh, if any1 is interested, the problem i have is in writing cds..it always fails at the lead in or lead out phase..
this is what Veritas recornNow! said:
"Disc Write Error - Sense:03 ASC:0C ASCQ:00 (Command:00)"
and this is what sony drive check said:
"Status : Error Problem : 04 - Internal Action : 04 - Abort w/ Shutdown
Description: SCSI Sense - Key:3 (Medium Error) ASC:02 ASCQ:00"

(might make sense to some1!)