I'm trying to troubleshoot a Renishaw H-2000-5062-07-A optical receiver for a tool piece used in a milling machine. It has several of these 8-SOIC(?) parts and I very much suspect that they are optoisolators with transistor outputs. The package is of a white plastic typical to many optoisolators and it is 5mm wide. What looks to be a manufacturer's mark is the letter Q with breaks in the ellipse at 2, 6 & 10 o'clock. That's followed by the number 206 and below that is 045S. I've had no luck finding a company that used that Q marking or those numbers. Does anyone have any information on this part? Thank you!
Logo does not match, but perhaps a pin compatible version of Fairchild/ON MOC206 optocoupler with transistor output?
The logo resembles QP semiconductor, but I don’t find anything pointing to them making optocouplers.
I think it's from QT Optoelectronics, which was acquired by Fairchild in 2000 Fairchild was then swallowed up by ON in 2016.
The part does not appear in QT's 1995/6 databook, which is available online, but's most likely MOC206-M as @winny suggests (+1), and the ON part should be a match. Optoisolators do tend to age due to the LED losing brightness, especially if it is driven hard.