Products > Test Equipment
HP8595E spectrum Analyzer: readings at -40dB and CAL SIGNAL NOT FOUND
<< < (6/8) > >>
auato:
Thanks a lot.
I finally disassembled the RF assy and opened the attenuator. At first glance what I found is the first relay on the right side (near the RF input connector) in a different position than the other relays (as vidible in the short video I published). Could this state be normal? Also, are the o-rings the tiny ones in the photo?

https://youtube.com/shorts/Yz_BRhvwg4g?si=0_UAxk8avDcMJ8Se


rf-loop:

--- Quote from: auato on December 17, 2023, 03:24:03 pm ---Thanks a lot.
I finally disassembled the RF assy and opened the attenuator. At first glance what I found is the first relay on the right side (near the RF input connector) in a different position than the other relays (as vidible in the short video I published). Could this state be normal? Also, are the o-rings the tiny ones in the photo?

https://youtube.com/shorts/Yz_BRhvwg4g?si=0_UAxk8avDcMJ8Se

--- End quote ---

Yes it is normal. Relays are bistable and they stay in position what was last commanded.
You can move these relays manually up or down. They have two position.

In your image can see this one O ring. Each nylon(or whatever material it is) lift-push pin is attached to the metal plate of the relay with two O-rings. There are two of these pins on the every relay plate. (The metal plate of the relay has a U-shaped hole where the pin and the O-ring are. It does not fall out of the slot because the hole through which the pin passes acts as a guide.) The pins go through the thin hole into the attenuator cavity and there these move the contact strips. The structure of the cavities inside is very delicate.
Often the pins are almost white, but in your case they are brown. It is perhaps older version. In my experience, brown pins are more prone to breaking than white ones.  (what is your analyzer serial number prefix what tell manufacturing year)

Move each relay to the lower position and to the upper position so that you can see the condition of the O rings as accurately as possible. Look closely. You  can easy move these up and down... (magnetic construction keep it in each position) 
The movement of that pin must be full. A missing, crumbled, etc. missing O-ring no longer pushes/pulls the full distance and the movable strip does not make contact in the cavity. Sometimes a small chip may have detached from the O carriage, which can prevent the full range of motion.

I can't find the full documents I made a long time ago about them and I don't remember the order of the attenuators.
However, the first one after Input is the DC-block. The next one is pretty sure 10dB, but I'm not sure right now if the order after that was 20 - 40 or 40 - 20.

If all the o-rings are fine and the movement is normal, pin need move exactly same amount than relay plate... then need to think about another possibility. One possibility is that the end of the nylon needle in the attenuator cavity is damaged and it no longer closes the contact that bypasses the attenuator chip in question. However, it can still work in such a way that you can push the contact into the attenuator position. yes, at least in theory, but I've never seen such a case. 


scopeman:

I have rebuilt these attenuators but sometimes it's worth it to consider other alternatives.

If all else fails you can send the attenuator out for a full rebuild at the company at the link below. I had them totally rebuild an attenuator
for my HP 4407B (9KHz-26.5GHz) a job that I could not easily certify in house so I sent it out.

They did an excellent job and I got certified plots of every attenuator step. I have no personal stake in this company, I am just a satisfied customer.

It's not cheap but you get a 1 year warranty. Something to keep in your back pocket when you need it.

https://www.testequipmentplus.com/agilent-hp-step-attenuator-repair.php

Sam
W3OHM
Kean:
More info on repairing the 33321 step attenuators can be found in this post:
https://www.eevblog.com/forum/testgear/hp-8644b-attenuator-question/
bg1wxd:
MY ENGLISH IS NOT GOOD ENOUGH, I FIXED THE ATTENUATOR OF THE HP 8595E, IT WAS THAT LITTLE BLACK RUBBER RING THAT WAS AGED AND BROKEN, AND A BOX OF RUBBER RINGS BOUGHT FROM AMAZON COULD BE REPLACED.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod