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Guest
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 Posted:
Wed Jun 15, 2005 6:34 am Post subject:
Can you help with a vexing microwave problem? |
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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. :-)
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John Miles
Guest
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| Posted:
Thu Jun 16, 2005 12:25 am Post subject:
Re: Can you help with a vexing microwave problem? |
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In article <1118799288.293607.234780@o13g2000cwo.googlegroups.com>,
bobd426@yahoo.com says...
| Quote: | Thanks in advance for any help. This is a heck of a puzzle for me. :-)
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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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http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
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Guest
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| Posted:
Thu Jun 16, 2005 12:35 am Post subject:
Re: Can you help with a vexing microwave problem? |
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| Quote: | A hair dryer/can of Freeze-Mist to the ALC board is the next, and
hopefully final, step.
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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.
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