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Absolutely agree on using surgical swabs, I should have mentioned that. And don’t flood the attenuator with isopropyl or spray on contact cleaner. I’ve replaced more o rings that had turned to gunk than I have brittle ones, but a fair number of brittle ones that i have replaced had left loads of little black rubber chips everywhere.

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If you have dirty pads usually your loss will roll off at lower frequencies and then normalize at higher bands , this is because the dirt in essence is a series capacitor creating a high pass characteristic ,? you can check this by putting a 50ohm termination on one side of your attenuator and connect a multimeter on the other side between center conductor and ground and then measure the resistance for each pad setting , it should read close to 50ohm , if it is higher than this points towards dirty pads or a blown pad !

In my years fixing those beasts back at tucker the most common issue I saw was bad o-rings .

If you pull off the cover of the attenuator cover and look at the solenoids you see the plungers that actuate the contacts , you see little white pushrods that are connected to those plungers , there should be a black o-ring visible on top and bottom ,? usually over the years the rubber becomes bridle and then falls apart , if this happens the contacts no longer make sufficient contact and the attenuator fails .

Agilent used to sell those as spare parts but you can also find them at watchmakers supply stores as they are used as sprocket gaskets , the company I ordered them from was otto frey/borrell if I remember correctly but this was like 20 years ago

One more hint on the cleaning part ,? avoid using regular cotton swabs as they fuzz , use techspray swabs or you can also use surgical swabs you can get at medical supply stores

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Sent from for Windows

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From: [email protected] <[email protected]> on behalf of Steve - Home via groups.io <steve-krull@...>
Sent: Thursday, March 3, 2022 7:00:40 PM
To: [email protected] <[email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8341B RF sweeper has reduced output

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In the 8340/41 the output power indicator is measuring power before the attenuator so will indicated “requested” power, not actual output power. Band 0 is 10 MHz - 2.3 GHz, the swept LO is mixed with the phase locked 3.7 GHz oscillator.?

Remove the front panel, remove the attenuator, loosen the end caps of the attenuator (8 Allen screws) remove the nuts from the SMA connectors for RF in and out, remove the name plate, remove the 20 hex head screws holding the front plate and SMA connectors and GENTLY pry the front plate off. The attenuator pads are attached to the front plate. Clean the contacts for each pad with 99.9% isopropyl alcohol. Clean the through lines the same way. Usually clears the problem.?

Steve

WB0DBS

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On Mar 3, 2022, at 5:56 PM, charlesterrebonne@... wrote:

?Hi all

My HP 8341B sweeper looks like output down 10dbm~13dbm from requested level output...measured on a Boonton 4200 power meter know good.?

I rarely use it above 1Ghz... IIRC <2Ghz is band 0 didnt test other bands. I suspect an output step attenuator problem? a 10db pad "stuck"?

Looking at power meter at right of front panel on 8341B I see it matches requested power output...shouldnt be showing -10~13dbm down from requested value if there is an attenuator problem since that value is measured at output?

Anybody very familiar with these HP sweepers suggestions/tricks to save me time to address this? Ive fixed lots of test equipment but never this 8341B and its a *75 pound beast* that id like to fix and put back where it lives asap...its no fun to handle, flip over and move...

Thanks all