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Agilent Technologies Noise Sources: 346A, 346B, N4000A, and N4001A
NOTE: This Installation Note also applies to the replacement of the 00346-60001 and N4000-60001 printed
circuit boards. To replace the PC board, please order the 00346-60157 (for 346A/B) or N4000-60016
(for N4000A/1A) Replacement PC Board Kit.
The replacement parts listed in Table 1 are tested in the factory to determine the bias current level necessary to ensure
that it meets ENR specification.
For the 346A and 346B, bias levels are determined by installing the appropriate resistor value for R7 on the printed
circuit board (Figure 1- 00346-60001). The appropriate resistor is supplied with the part.
Replacement Bulkheads for the 346A and 346B have the recommended bias level written on the part. The appropriate
resistor is enclosed in a small envelope. The resistor value and part number are written on the envelope. The
N4000/1A bulkheads are not supplied with an envelope and resistor. However, the value of the current is marked on
the part.
00346-60154 Replacement Noise Cartridges are used in all the listed models. These parts are labeled with a tracking
number. The appropriate resistor is enclosed in an envelope which is marked with the tracking number of the
cartridge, resistor value, part number and recommended bias current level. Also, the cartridges are shipped with
Installation Note 00346-90024, Attenuator Replacement, in case attenuator tuning is necessary to bring the unit to
within specification. It may be necessary, in rare cases, to replace the attenuator to meet specification.
On the N4000A and N4001A models, the bias is set electronically by using field calibration software to calibrate the
Noise Source and re-burn the EEPROM. The bias value of current supplied with the Replacement Noise Cartridge is
to be used to program the sensor. The enclosed resistor can be discarded.
A.1 346A/B Replacement Noise Cartridge Installation Instructions:
1. Ensure that the cartridge was shipped with a resistor contained in a small envelope.
2. Ensure that the tracking number on the cartridge matches the number on the envelope.
3. Ensure that the value of the current marked on the envelope corresponds to the resistor value and part number
provided (refer to Table 2).
4. Ensure that the resistor value on the envelope matches the resistor supplied.
5. Ensure that Installation Note 00346-90024 has been provided.
6. Disassemble the Noise Source by removing the two flat head screws near the output connector and slide the
bulkhead out of the housing.
7. Next, remove the two flat head screws near the BNC connector and slide out the printed circuit board assembly.
8. Remove the old cartridge from the bulkhead and install the replacement cartridge.
Ensure that the tiny bellows remains on the attenuator pin.
9. Check the resistor installed in position R7 on the 00346-60001 printed circuit board; please refer to Figure 1-
00346-60001. If it matches the resistor supplied, it is not necessary to install it in the printed circuit board.
10. Install the supplied resistor in R7 position (refer to Figure 1- 00346-60001).
11. Reassemble the unit and do a preliminary ENR measurement.
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