PNA Front Panel Lockup Solution

This page describes how to solve the problem where the front panel keyboard and knob (RPG) stops functioning. This could happen to any PNA with the E8361-63061 front panel board. This is an intermittent problem; cycling power will usually make it function again. This issue does not affect the PNA-X (N5242A) or any PNA with a serial prefix of 4700 or higher (e.g. MY4700xxxx or US4700xxxx.) While Agilent will fix this problem for free if the PNA is sent in for any type of service, customers can perform the modification themselves if they are concerned about turnaround time. The only requirement is a soldering iron with a fine tip and reasonable soldering skills. A large magnifying glass is also useful. Once the front panel is accessible, the repair only takes a few minutes.

This problem has been traced to an incorrect voltage applied to an IC. The modification consist of removing a series inductor (to remove the voltage), and shorting two adjacent pins together on the IC (to apply the correct voltage.) Refer to the service manual for complete disassembly instructions. Below are the summarized instructions.

1. Remove the 4 rear feet and side straps.
2. Remove PNA's outside cover.
3. Remove the 4 screws on each side that hold the front panel assembly to the frame.
4. If your units has front panel loops (semi-rigid cables), remove them. You should label them so that they can be replaced back to their original positions.
5. Remove the ribbon cable that is attached to the front panel.
6. Separate the front panel assembly from the PNA. The front panel board should now be easily accessible.

• Modification #1 consists of shorting two pins of U4 together with a small amount of solder.
• Modification #2 consist of removing L1.

Modification #1

Carefully solder pins 21 and 22 together on U4. Refer to Figure 2 for the exact location. Use care so that no other pins are shorted. Use of a very fine tip soldering iron is recommended and a large work-task magnifying glass is very helpful.

Modification #2

Identification Items

When the modifications have been completed, you need to change the board revision number from its existing version to version 009. You can cross off the existing revision label and write in "009" or you can create your own label to place over it.

Look at the date code on the side of the RPG (Rotary Pulse Generator or optical encoder). If the date code is between 0609 and 0718 (inclusive) then skip this step and read the next paragraph. Otherwise, remove the front panel knob and place a large black dot on the end of the RPG shaft using a permanent marking pen and then replace the knob. This will indicate to others (service centers and repair personnel) that this modification has already been made. This location is used so that the PNA does not need to be first disassembled.

Warning! If the date code of the RPG is from 0609 to 0718, then you may have problems removing the knob. On these units, the RPG shaft may be pulled out of the RPG while trying to remove the knob, thus destroying the RPG. While Agilent will replace this for free, this would incur more unwanted downtime. For these cases you may just want to place a label on the back of the PNA, to the left of the CPU board. This label should read simply "FPI 009." If needed, the Agilent part number for the RPG is 1990-1865.

Conclusion

• Model # - Service Note
• E8356A - E8356A-02C
• E8357A - E8357A-02C
• E8358A - E8358A-02C
• E8361A - E8361A-02B
• E8362A - E8362A-01B
• E8362B - E8362B-01B
• E8363A - E8363A-01B
• E8363B - E8363B-01B
• E8364A - E8364A-01B
• E8364B - E8364B-01B
• E8364B - E8364B-01B
• N5230A - N5230A-01B