Can you help with a vexing microwave problem?

I need help!

I have a Wiltron 6213D dual band plug-in, 0.01 to 1.0 GHz and 0.01 to
4.2 GHz. It goes in the Wiltron 610D Sweep Generator. The plug-in works
fine for about 30 minutes, then the output leveling fails. The output
sweep signal is still there, but the level looks like a cross section
of the Rockies!

I do not have a manual for this plug-in but I do have basic knowledge
of microwave RF components - just not much experience above VHF HAM
bands.

Does anyone have a manual that I could get (or a copy), so I have some
idea of what I am up against?

Lacking (or in addition to) that, are there any knowledgable microwave
people out there that would like to help solve this puzzle? I have
already taken a lot of data, have a component assembly drawing,
pictures of the microwave components (for ID) and the RF signal (power
vs frequency from a HP431/478A to a storage scope) at various places
within the RF unit and the output. I don't think I can put .jpg files
on this list, but I can probably put a link to get at them on another
server.

Thanks in advance for any help. This is a heck of a puzzle for me.

 

A hair dryer/can of Freeze-Mist to the ALC board is the next, and
hopefully final, step.

Hi John,

Thanks for the suggestions. The last one seems to have worked. Since I
knew least about the microwave components, I naturally looked there
first! What the heck, even if I did not find the solution, I was bound
to learn something.

Freeze-Mist did nothing to the RF components, but it sure had a major
effect on a LF13201N JFET analog switch. This component was running 30
F hotter (140F) than another on the board, so probably was leaking. I
ordered a new one, so we will see.

I still would like to find a copy of a Wilton 6213D RF Plug-in manual
if someone has one laying around.