Jeff,
re-fitting a different YIG was an option which I was thinking about when I repaired my 8341A sweeper. The YIG is a 5086-7323 which operates from 2.3 to 7GHz and tuning coil sensitivity is 24mA/GHz. However, I wonder how accurate those 24mA/GHz are. For instance, if I fitted another YIG with 20mA/GHz, would that work as well? the YO driver used can be calibrated for offset and gain... Have you ever fitted a replacement YIG?
What about those SYTMs HP has used sometimes (switchable YIG tuned multiplier)? is there any replacement?
And do you have an idea what the reason could be for the semiconductor to fail? assuming the operating voltages were ok, is there some chemical aging process or so which destroys the semiconductor some day? because there are instruments which are 30 yrs old and still working, but the older they get the more difficult it will be to find spare parts I guess; if the YIG fails and cannot be replaced, the whole instrument is nothing more than a really heavy paperweight....
Tobias HB9FSX
-------- Original message --------
Date: 10/16/17 06:01 (GMT+01:00)?
Subject: Re: [hp_agilent_equipment] YIG device failure modes?
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I have tested several hundred YIG devices over my career. (Have drawers full of them, its a sickness)? I have seen more misaligned YIG support rods or bad oscillator semiconductors than I have seen bad coils.
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Sometimes the coil connection fails at the solder point due to wire wrap/crimp failure and current heating the joint, eventually it opens, have fixed three like this. Some model YIGs have high coil current and if poorly cooled/heatsunk, the enamel insulation seems to fail and create a sorted coil. Only have seen one like this, but opened it up and figured out the failure.
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Other times, the polystyrene rod that holds the YIG sphere warps & twists over time from heat?& general plasticizer failure?and misaligns the magnetic axis of the sphere with the field, pretty tough to fix this, major cause of holes and high end tailing off.?
And, of course, when the semiconductor device fails (Gunn diode in older X band and up, Bipolar thru 12 GHz for old ones, FET now), you are done.
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It is possible to re-fit different YIGs into various pieces of gear, but re-scaling the drivers to the right coil sensitivities can be challenging/time-consuming.
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The worst thing to deal with is the wideband? YIG tuned multipliers. Never had much luck bringing these back to life once they go south.
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YMMV
Jeff Kruth
WA3ZKR
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Hi guys. Over the years I have read a lot about yigs going bad specifically their coils seem to go bad. Is there anything that can be done pre-emptively to secure their longevity? And what exactly happens? Do the coils open due to excessive current (like a fuse?) I know there is an issue where the sphere sometimes moves and gets located incorrectly IIRC. I don’t know what causes that, perhaps excessive force? But I am interested in the coil issue. I have no yig issues at the moment, which seems like a good time to try to prevent it?
Eugene W2HX
