Service Information
Coaxial RF Power Standards Instruction an Service Manual
6-3
Repair Parts
Due to the calibration sensitivity of this instrument, it is not recommended to remove or replace
any RF components within the RF Power Standard. In the event that damage or a malfunction has
occurred, return the unit to TEGAM for repair and calibration. If the user chooses to replace an
item within the RF Standard such as a connector or defective cable, the instrument must be
recalibrated.
Preventive Maintenance
While the RF Standard requires very little preventive maintenance, it should not be subjected to
physical abuse, severe mechanical shock, high humidity, or operating temperatures outside the
specification range. The instrument should be kept free of excessive dirt and dust, since these can
interfere with connector functions and with normal heat dissipation.
Connectors
Care should be taken to prevent strain on the interconnecting cables, since damage here may not
always be apparent. Occasionally check the external cables and connectors for signs of cracked
insulation and/or bent or worn pins. Tests show that connectors must be clean for accuracy and
stability. This requires an inspection and cleaning of each connector immediately before use.
When cleaning precautions are observed regularly, connectors can maintain their stability for over
several thousand connection cycles.
Where small amounts of rust, corrosion, and/or oxide deposits are present on connectors, clean
externally with a soft-bristle brush, aluminum wool, or internally with an acid brush; then wash
with a noncorrosive solvent. MIL-C 83102 is recommended. Exercise care to ensure no metal
filing or residue remains inside the connector and the connector is thoroughly dry. Where rust,
corrosion, and/or oxide deposits are present in large quantities, replace the connector.
Calibration
Since the stability of the calibration factor of a thermistor mount depends upon the extent of use,
degree of temperature stability and care in handling, TEGAM recommends recalibration of the
standard every year. To recalibrate the unit, use one of the following methods:
1.
Return the RF Power Standard to TEGAM indicating that recalibration or repair is
necessary. TEGAM provides NIST traceable calibration of K
2
(Working Standard) and K
1
(Reference Standard).
2.
Send the Reference RF Power Standard to NIST (or other national standards agency) for
recalibration. NIST only provides K
1
calibrations.
3.
Calibrate the Working Power Standard using a Reference Power Standard as described in
Section V Maintenance.
Troubleshooting
Despite their sensitivity, thermistor beads are sturdy elements that can withstand up to 0.2 Watts
for burnout. However, a burnout condition is eventually possible. An “open” reading at the DC
bias binding post indicates a burnout condition. TEGAM power measuring instruments such as the
Models 1805B, 1806(A), and 1804 have an “Error” light that will also indicates a burnout
condition.
High SWR or incorrect calibration factors could indicate a defective power splitter or broken RF
connector.
The voltage across the bias terminals when RF power is not applied (bias voltage) is adjusted at
the factory to be within 2.42 to 2.48 VDC. If the bias voltage is not within this range there may
be a defective internal component. Bias voltage drift of more than 0.5 mVDC over a 24 hour
period (with the internal heater connected to a heater controller) also indicates a defective
internal component.
If any of these conditions exist contact TEGAM for service.
