Introduction; Access Procedures; Removing Analog Modules; Removing The Main Cpu (A9) - Fluke 5520A Service Manual

4-1. Introduction

Because this is a high performance instrument, it is not recommended that the user
service the boards to the component level. In many different ways it is easy to introduce a
subtle long-term stability problem by handling the boards. Access procedures are
provided for those who want to replace a faulty module.

4-2. Access Procedures

Use the following procedures to remove the following assemblies:
Analog modules.
Main CPU (A9).
Rear Panel Module (transformer and ac line input components).
Filter PCA (A12).
Encoder (A2) and display assemblies.
Keyboard PCA, and thermocouple I/O pca.
4-3.

Removing Analog Modules

Proceed as follows to remove the Voltage (A8), Current (A7), DDS (A6), or Synthesized
Impedance (A5) modules:
1. Remove the eight Phillips screws from the top cover.
2. Remove the top cover.
3. Remove the eight Phillips screws from the guard box cover. The locations of the
analog modules are printed on the guard box cover.
4. Lift off the guard box cover using the finger pull on the rear edge of the cover.
5. On the desired analog module, release the board edge locking ears.
6. Lift the board out of its socket in the Motherboard. Lay the board shield side down.
7. To remove the shield, remove Phillips screw at the center of the shield, then pull the
sides of the shield away from the board.
8. To reinstall the shield, first align one set of tabs then press the other side into place.
4-4.

Removing the Main CPU (A9)

You can remove the Main CPU (A9) without removing the rear panel or Filter PCA
(A12). Proceed as follows to remove the Main CPU PCA:
1. Remove the 3/16" jack screws from the SERIAL 1, SERIAL 2, and BOOST
AMPLIFIER connectors.
2. Remove the 1/4" jack screws from the IEEE-488 connector.
3. Remove the three Phillips screws from the right side of the rear panel.
4. Remove the ribbon cable from the Main CPU PCA (A9). There is not much room,
but the cable is reachable.
5. Lift out the Main CPU PCA.
Maintenance 4

Introduction

4-3