Maintenance
4
Keysight 478A Operating and Service Manual
39
If the meter is pegged upscale:
1
Set ZERO and VERNIER to mid-range.
2
Set RANGE to highest position which will not peg the meter.
3
Turn one of the screws (B) counterclockwise to obtain a meter reading half that
observed in step 2.
4
Turn the other screw (B) counterclockwise to zero the meter. If it is impossible
to zero the meter, replace the thermistors (see
5
Replace cover and three screws (A). The instrument is now operative.
Thermistor Assembly Replacement Procedure
The procedure consists of removing the damaged thermistor assembly, the
printed circuit assembly and replacing them with pretested assemblies included in
Thermistor Assembly Replacement Kit, Keysight Stock No. 00478-60002 (see
NOTE
After replacement of the thermistor assembly, the Effective Efficiency and
Calibration Factor indicated on the label of the mount are no longer valid (see
Table 4-1
Replaceable Parts
Keysight Part Number
Qty
Description
0520-0136
3
Screw, 2-56 x 5/8 , RDHD
0520-0173
3
Screw, 2-56 x 3/16, PNHD
1251-0153
1
Receptacle Connector
1251-1281
1
Nut, Knurled
1460-1547
1
Spring, Compressor
2190-0014
3
Internal Lock Washer No.2
2190-0036
1
Washer Lock, 818 ID
08491-2009
1
Sliding Contact
Содержание 478A
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Страница 45: ...Keysight 478A Thermistor Mount Operating and Service Manual 45 A Appendix A Introduction 46 Manual Changes 47...