Checking out a recently arrived OCP5502.
Fails on 'ZERO' operation.
TEMP indicator illuminated continuously.
Hot smell, faint smoke from region of optical receiver module after a minute or two...
Does indicate optical power, though off by ~1-2 db
From all of these symptoms, and a read of the manual, I suspect the detector temperature control loop is failed, and the heater is running full power. Have not left it on for more than a few minutes at a time so far...
Service manual..? Schematics..? Wisdom from those who have gone before..?
My hope is the problem is external to the detector module, and any hints as to where the thermistor(?) signal might be probed, and / or the pass transistor for the heater is located would be appreciated..!