HP 8555A spectrum analizer problem

[andreal1967]

hello everybody.
i am an hobbyst who is trying to fox an 8555A RF module with my little electronic knowledge. So i ask for help.

Here is the problem: the analizer work well if i select the scan bandwidth above or equal to 1mhz.
If i select 500 khz scan bandwidth or less i am not able to see the signal anymore. I have to figure where is located the failure because i have another 8555 for parts that i can use for troubleshooting.

here is a video to show the problem:



thanks from Andrea (italy)

[jonpaul]

Usually the rotary encoder switch wipers on the white delrin wafers behind the front panel switches.

VERY intricate to disassemble , repair and reassemble.

Suggest to take phots of the switches, probably will see missing switch armatures.

You will get much faster and better advice on the GROUPS.IO site for HP instruments!

https://groups.io/g/HP-Agilent-Keysight-equipment/topics

Bon Journee,   Ciao!

Jon

[andreal1967]

Hello jon Paul. The rotary switch was my first tought , as i have another Borrowed 8555a for test and troubleshooting i replaced the whole tuning assembly with rotary switch without solving the problem ( the tuning assembly works good on the other 8555A)