Ok, I refurbished the DW1640 and ran a scan. The results were good:
So I burned another one and scanned it. The result was more than double PIE and triple PIF. So I can’t do any more objective testing since they’re obviously decreasing in quality lower down in the spindle, as mentioned previously.
However, I proceeded to re-scan the July disc again, and this time I got a different result:
Baffled, I put my reference or ‘baseline’ disc (MCC 01RG20), and scanned it with the DW1640. The scan was nearly identical to the one performed on the DW1620 in July, with the PIF and PIE spikes in virtually the same places:
My DW1640 is working fine. It does in fact read lower PIE and PIF than the DW1620. What I don’t understand is the more significant fluctuation between the same F16 disc on two different scans on the same drive. That’s a point in favour of the suggestion posted elsewhere here on this forum that F16 degrades over time. So I’ll need to do some further testing before I reach any conclusions about F16.