Due to my job taking me round the UK. Friends, neighbours & even recently a relatively local dealer have been getting me to pick various pc components.
Lately the 1640 has been the most sort after. Today on picking up several units in the midlands. I got talking to the wholeseller. This conversation started when he overheard me saying that I sourced from around the UK.
However to the point, when buying a 1640 take a good look at rear of unit. Looking at bottom, pay particular attention the space between circiut board & bottom plate. You may see warped circuit board. This wholeseller reckoned this affected about 2% of the stock they had seen.(OEM)
How this may or may not affect the drive is debatable. But a lot of returned stock (not all) would appear to have warped boards. Obviously this could happen as a result of badly vented case's/overspeeding etc.
But be on the look out it may save you some time to do other things.