So, bought an Ignis 660 in supposedly working order with a defective driver. Went through the driver but couldn't really find anything wrong with it, but did find that it won't put any current through the diode without an external mod signal; the LQ application does indicate 100% current, but checking the sense resistor shows no voltage without the mod signal, so perhaps that is the 'fault'.
Anyway, with a mod signal applied, I was getting less than 1 mW; I carefully tweaked the KTP temp to find all the peaks, the best peak gave me 6mW. I then tuned the diode temperature but found it was already optimal. So, I have a 500mW rated 660nm head doing 6mW I checked the diode current and it's circa 7.5A at 100% drive.
Checking the interface, the elapsed time shows about 30K hours, so I guess it's well and truly worn out. Can the diode be replaced in these, or is it a moderately expensive paperweight?