Hey everyone,

?

I recently picked up an 853A analyzer mainframe and two 8559A 10M-21Ghz modules. Of course, it's broken.

They all power up just fine but all I can get on the screen is an horizontal line in the upper section of the screen. It's as straight as it can get. It does seem to respond to the settings as the beam varies.

It's a complex instrument and I'm not familiar with it. Does anyone have an idea what's going on with it? I suppose it may be in the mainframe as two modules, although unknown, give the exact same results.

These modules (8557-8559) tend to have issues related the mechanical switches.? The finger contacts like to fall off.? They can be replaced with fingerstock.? Specifically, fingerstock from Tech-Etch part # 75RE or from Laird Tech part # 97-134.? The problem is the manufacturers of these fingerstocks only sell in large quantities.? But perhaps you can reach out to them for sample.? Or get lucky like I did and find some used on eBay.? These part #s are almost a perfect match to the original HP contacts.? But you can also make your own some other way.??

?

Unless I'm misunderstanding your post, and you're saying the horizontal line appears without plug-in installed.? Then of course the mainframe is where to start.? Troubleshoot the issue without the plug-in installed.? The HP 853A service manual is very thorough and can be found online for free. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.keysight.com/us/en/assets/9018-03045/user-manuals/9018-03045.pdf?success=true

Yes I am aware of the switches issues. They're gone but I have enough to make one working and good looking unit.

?

Just do describe the situation more precisely:

- With no module, I get a single dot on the screen

- With one module I get the same

- With the other I get a vertical line that I can change with the sweep speed dial, so it's probably doing or trying to do something. The output cal was working althought a little powerful.

?

On the initial startup with the good module I got some weirdness in the lower half. That looked like characters to me.

I've added photos. Sorry it's so dirty, I'll clean it tomorrow.

?

I don't have the mainfraime 853A service manual, I can't find it in the group files either. In the user manual (chapter 1 page 1) they say that you can access a test routine for setting up the screen position and focus by starting the unit with the PLOT GRAT button depressed, but it doesn't work on my machine. I'm thinking that both of my modules are bad, but there's also something in the mainframe??

Hi Dave,

?

I planned on doing this. I keep the intensity down, I just increased it for the photos because my phone needed it.?

?

Thanks

Arnaud.