[time-nuts] HP5065A Rubidium question

timeok timeok at timeok.it
Mon Feb 20 01:47:20 EST 2017

   Hi Scott,
   I have never find a photodiode faulty. When applied 20 volts to the lamp it should come on within about 10 seconds, and the PHOTO I meter on the panel will be between 20 and 50. If this does not happen the most probable failure is the resistance R1 on the lamp board (1330ohm 2W). In this case, I suggest you replace it with two 2700-ohm 1W resistors in parallel.

   Other faults that I found were: the broken transistor Q1 and the exciter coil detached from one side, but these failure are very rare.
   let me know,

   There is 20 VDC feeding the RVFS lamp oscillator.

   But, there is no current coming from the photodiode. (Maybe a few picoamps of dark current, certainly not the expected ~50 microamps of DC, and no 137/234 Hz signals).

   It seems the most likely problem is that the Rb lamp is not coming on. Maybe possible that the photodiode is faulty, or a broken wire, etc.

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