Build from some power supply things and a PICOMETRIX PT-10B
The PDA8GS from Thorlabs is a High-Sensitivity PIN Detector, 750 - 1650 nm, Fiber Coupled, 9.5 GHz. It was brought to my lab because
"the green light went off".
✈ Measurements • Discoveries
As with other devices which are not working, one usually follows the path of the supply voltage. In this case it could be seen that the switch is working fine,
but the voltage after the fuse was gone. It turned out, that the fuse had a high impedance, whilst after the fuse a low impedance to ground could be observed.
(That was he reason for the fuse to break). Three components after the fuse were put on the list of suspects. The capacitor C1, zener diode D2 or the DC/DC converter
NMH1205D. It turned out, that the zener diode was the reason. As it was rated 15V, the conclusion is, that the user applied a voltage higher than 15 V
(or a reversed supply). This caused the diode to conduct (and fail) and finally the fuse to break.
The schematics above is from our device. It may differ for yours. NO, we do not repair your photodiode.
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