[time-nuts] Z3801A OCXO manual trimming

Joe Hobart nova at npgcable.com
Sun Mar 4 13:13:06 EST 2018

My Z3801A failed about a year ago (there was a warning the electronic frequency
control was nearing a limit).

Symptoms (most from GPS Control and Lady Heather:

   Frequency about 1E-8 low

   Time Invalid  (many hours off)
   Date 6 months old
   DAC 99.9969 percent
   Life 72K Hours

Lady Heather shows the following as OK:

   ROM, RAM, OSC GPS, Power, EEPROM, Antenna, Discipline, 5 satellites

GPS Con shows the following:

   No time display
   Outputs Invalid

Only the front panel power light is lit.

This suggests either the crystal has aged or the heater temperature has drifted
slightly.  I hear/read that opening the oscillator is difficult.  Is there a
usable adjustment?

What have others done to restore operation?  Is it time to consider a different
time & frequency standard?

Joe, W7LUX

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