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Issues with Datum FTS 4065A cesium beam reference

A(
AC0XU (Jim)
Mon, Jul 27, 2020 1:48 AM

Time Nuts-

Having fixed the dead power supply on this Datum FTS 4065A, the control panel displays mostly "Major" fault, although this occasionally shifts to "Minor" fault for a brief time. It reports Cesium Module faults that vary from time to time. They are usually one of:

2,18
2,3,18
2,3,7,18

According to the 4065C manual, the codes mean:

2 - Voltage difference (symmetry check of clock transition) > 40 mV
or
Voltage difference (clock pedestal) >40 mV

3 - Voltage difference (Zeeman pedestal) >160 mV

7 -  DAC voltage < 5% or > 95% of input range

18 - Beam Gain DAC Near Limit

Is there a straightfoward way to determine whether the tube is dead or - how should I drill down??

All voltages displayed by the control panel seem to be within range. Oscillator shifts from 'COLD' to 'warm'. There is a 10 MHZX output signal but it is not especially stable.

Thanks in advance-

Jim

Time Nuts- Having fixed the dead power supply on this Datum FTS 4065A, the control panel displays mostly "Major" fault, although this occasionally shifts to "Minor" fault for a brief time. It reports Cesium Module faults that vary from time to time. They are usually one of: 2,18 2,3,18 2,3,7,18 According to the 4065C manual, the codes mean: 2 - Voltage difference (symmetry check of clock transition) > 40 mV or Voltage difference (clock pedestal) >40 mV 3 - Voltage difference (Zeeman pedestal) >160 mV 7 - DAC voltage < 5% or > 95% of input range 18 - Beam Gain DAC Near Limit Is there a straightfoward way to determine whether the tube is dead or - how should I drill down?? All voltages displayed by the control panel seem to be within range. Oscillator shifts from 'COLD' to 'warm'. There is a 10 MHZX output signal but it is not especially stable. Thanks in advance- Jim
MD
Magnus Danielson
Mon, Jul 27, 2020 7:56 AM

Hi Jim,

On 2020-07-27 03:48, AC0XU (Jim) wrote:

Time Nuts-

Having fixed the dead power supply on this Datum FTS 4065A, the control panel displays mostly "Major" fault, although this occasionally shifts to "Minor" fault for a brief time. It reports Cesium Module faults that vary from time to time. They are usually one of:

2,18
2,3,18
2,3,7,18

According to the 4065C manual, the codes mean:

2 - Voltage difference (symmetry check of clock transition) > 40 mV
or
Voltage difference (clock pedestal) >40 mV

3 - Voltage difference (Zeeman pedestal) >160 mV

7 -  DAC voltage < 5% or > 95% of input range

18 - Beam Gain DAC Near Limit

These is in increasing order of severity.

Is there a straightfoward way to determine whether the tube is dead or - how should I drill down??

All voltages displayed by the control panel seem to be within range. Oscillator shifts from 'COLD' to 'warm'. There is a 10 MHZX output signal but it is not especially stable.

One of the things to care about after having a major power-fault is that
the oscillator may need time to recover. Locking it up while it is
drifting and being too far of frequency upset any cesium. Measure the 10
MHz and let it settle. Only after it has settled one may consider tuning
it. If it is close enough it may lock up, and that goes quicker with a
more accurate 10 MHz straight from the OCXO.

Locking onto the Zeeman and then clock transition becomes easier.

Cesium locks goes quick by H-maser standards.

Cheers,
Magnus

Hi Jim, On 2020-07-27 03:48, AC0XU (Jim) wrote: > Time Nuts- > > Having fixed the dead power supply on this Datum FTS 4065A, the control panel displays mostly "Major" fault, although this occasionally shifts to "Minor" fault for a brief time. It reports Cesium Module faults that vary from time to time. They are usually one of: > > 2,18 > 2,3,18 > 2,3,7,18 > > According to the 4065C manual, the codes mean: > > 2 - Voltage difference (symmetry check of clock transition) > 40 mV > or > Voltage difference (clock pedestal) >40 mV > > 3 - Voltage difference (Zeeman pedestal) >160 mV > > 7 - DAC voltage < 5% or > 95% of input range > > 18 - Beam Gain DAC Near Limit These is in increasing order of severity. > Is there a straightfoward way to determine whether the tube is dead or - how should I drill down?? > > All voltages displayed by the control panel seem to be within range. Oscillator shifts from 'COLD' to 'warm'. There is a 10 MHZX output signal but it is not especially stable. One of the things to care about after having a major power-fault is that the oscillator may need time to recover. Locking it up while it is drifting and being too far of frequency upset any cesium. Measure the 10 MHz and let it settle. Only after it has settled one may consider tuning it. If it is close enough it may lock up, and that goes quicker with a more accurate 10 MHz straight from the OCXO. Locking onto the Zeeman and then clock transition becomes easier. Cesium locks goes quick by H-maser standards. Cheers, Magnus