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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. :-)

Reply to
bobd426
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Manuals seem scarce for that one! Both my usual sources (Consolidated Surplus and Manuals Plus) bombed out.

It shouldn't be hard to figure out what's up, though. If you poke around on the output fitting assembly with a scope or voltmeter while varying the amplitude, you should find the terminal where the rectified sample of the RF voltage is extracted. It will probably be less than a couple volts at full-scale output. See if that voltage is still present when the unit acts up. If not, the output sampler is your problem.

If so, find the mixer/modulator assembly, or whatever Wiltron calls it. I believe they used HP PIN modulators in at least some of these plugins. It will have RF in/out ports and a third control port where the ALC circuit applies a current to control the output amplitude. Measure the current and/or voltage here and see what happens to it when the symptom occurs. Depending on what you see, that may give you some ideas where to look. You may have to open the loop by disconnecting the output sampler connection and applying a constant voltage to tell exactly where the fault is occurring.

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

-- jm

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Reply to
John Miles

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.

Reply to
bobd426

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