I already have reported in this entry that REFL165 shows too high DC output which does not depend on the light level on the diode.
Today I removed REFL165 from the table and inspected it.
The diode has been burnt as shown in the first picture (left).
The window is smoked, and the photo sensitive surface has been removed from its base. It moves in the can.
The burnt diode was replaced to the new one.
The new one shows ~30% better capacitance of ~50pF and I had to increase the inductance from 14nH (i.e. 15nH//220nH) to 18nH.
After some struggles to increase/decrease the stray inductance by moving the SMD capacitors a little, the resonance is reasonably tuned to 166MHz.
The comprehensive test will be performed shortly. |