Kiwamu mentioned that REFL165 is not responding and its DC out seems saturated at 9V. Koji and I checked to see if changing the power supply to the PD changed its behaviour. It did not.
I then look a close look at the PD and found that the front window of the PD was not clear and transparent. There was a liquid condensation inside the window, indicating an over heating of the PD at some point. It could have arisen due to excessive incident power. The pic below shows this condensation:
I also checked the current flowing through the reverse bias voltage line. There was a voltage drop of 3V across R22 (DCC D980454-01-C) indicating a 150mA of current through the PD. This is way too much above the operating current of about 20mA. The diode must have over heated.
I pulled out the old PD out and installed a new one from stock. The pic below shows the clear window of a new PD.
After changing the PD I checked the DC output voltage while shining a torch light on to the PD. It showed an output of about 30 to 40 mV. This seemed okay because the larger 2mm photodiodes showed ~100mA DC output with the same torch.Below is the current state of the ckt board.
I will tune the PD to 165 MHz tomorrow and measure its transimpedance.