ADC (Advantest's T&M arm) wouldn't say a thing other than "manuals are not for customer distribution". They passed me onto Rohde & Schwarz, who stated the same thing but a bit more clearly -- ADC make service data available to R&S under a non-disclosure agreement. They may be allowed to acknowledge that "certain manuals" exist, but not provide any details as to their contents. TL/DR, there's no way I'm getting a service manual for this or any other ADCMT or Advantest equipment.
(testgear manufacturer shitlist now reads: ADCMT / Advantest, SRS -- in SRS's case because of their "if you aren't the original purchaser, we won't help you" policy)
It turns out one of my meters is fairly completely pooched. The highest-gain signal range works OK, but as soon as the meter selects a lower-gain range (e.g. /10 nW) the meter acts like an integrator -- the indicated reading creeps up to full scale, then the display reads "1 " (overload). The bargraph follows the indicator. I'd be interested in any ideas people might have for fixing this one, though I may desolder everything, scan the PCBs and derive a schematic set. "Just because I can".
The second meter had two ruined (corroded) switches, a few damaged tracks and a ruined sensor head connector. I've acquired a new head connector (it's a standard part, a Hirose HR10A 12-position panel mount push-lock circular socket) and will be looking to solder that together this weekend. In the meantime, I've robbed the connector and switches from the dead unit and pieced together something vaguely resembling a working optical power meter
My "thin" optical sensor head is reading zero, so that needs looking at, but the other two seem to work fine (or as fine as can be expected when you feed an IR laser sensor light from a cheap red laser pointer...) Plan of action is:
* Put the new connector on the backplate, solder wires, install in LPM
* Pick the cleanest / most intact case plastics and other cosmetic parts, make a nice looking meter from that.
* Final clean up, get the last of the gunk off the brass threaded inserts, then reassemble the meter
* Fix the "thin" sensor or find another (probably need to set up an ebay watch for Advantest LPM sensors which work with this meter)
And for later:
* Reverse engineer the analog board, figure out if there's any reasonable way to use these sensors on a custom test rig (academic point more than anything)