[3dem] Problems with Gatan US4000 blankers

[Chen Xu]

Dear Pasi,

Here is what I think. 

Because this problem started with new US4000 controller, I would first
suspect the Gatan hardware. LEDs blinking doesn't necessarily mean
shutter signals being sent to X10 or/and X11 successfully. I would
disconnect the BNC cable at X10 and measure the output of Gatan shutter
signal using a voltage meter. If you don't see the 5V signal when large
screen is UP and 0 when it's down, then I would ask Gatan. 

If you do see the shutter signal, then I think it is more likely the FEI
software issue. You did not say your Tecnai version, but I believe since
4.0, the external shutter control is solely via software, you should not
use override cables anymore. I have attached a picture where you can see
the FEI handles shutter control to Gatan (external) when CCD is
inserted. You should be able to see "ShutterCoilExternalDrive" being
checked automatically when large screen is UP and unchecked when DOWN.
If it is never checked when large screen is UP, then it means Gatan
doesn't control the shutter, so beam stays on all the time. We had an
opposite case with our F30 that when CCD is inserted sometimes we got
blank films. In this case, the ExternalShutterDrive is never
disconnected. We "work around" this by retracting CCD before each film
exposure. 

I hope this can be helpful, let us know what you find out. 

-Chen
Brandeis Uni.



* Pasi Laurinm??ki <pasi.laurinmaki at helsinki.fi> [131120 02:18]:
>
>Dear EM community,
>
>I wonder if some of you have experience with problems regarding the
>beam blanking by Gatan Firstlight control unit.
>
>Our system: FEI Tecnai F20 & Gatan Ultrascan 4000 & Gatan Digital Micrograph
>We have recently had the power supply in the Firstlight break down and
>then replaced. After the replacement, operation was ok since we could
>do all the calibrations as well as normal imaging.
>
>However, now we have a problem. In short, the beam doesn't blank when
>it should (Situation: flood beam)
>-if I look at dark reference it has high counts
>-flood beam image, if dark corrected, has near-zero counts (because
>dark ref is "hot")
>
>When images are taken blanker led's in the front panel of Firstlight
>flash on and off as normal. If (as Gatan specialist suggested) I
>disconnect override-cable from back of firstlight I should be able to
>see (with viewing screen down) the beam blanking on and off as the
>image is recorded. This doesn't happen, the beam stays on constantly.
>
>I have tried different shutter idle settings under DM camera config.
>My shutter idle settings are now both shutters closed. I have checked
>the shutter cables (running from back of Firstlight shutter 1 and
>shutter 2 to microscope cabinet X10 and X11) and they look fine. Under
>camera acquire advanced settings i have tried both pre- and
>post-specimen shutter. To my understanding, because Firstlight
>frontpanel leds show operation, the fault is somewhere between
>Firstlight intelligence and the actual physical blankers in the
>microscope cabinet.
>Is it possible that the problem is in the microscope hardware? How to
>check for that?
>
>Looking forward for your suggestions,
>-Pasi Laurinm??ki
>
><<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>
>Pasi Laurinm??ki  Laboratory Engineer
>
>Institute of Biotechnology
>Electron Microscopy Unit
>P.O.Box 56
>FIN-00014 University of Helsinki
>Finland
>
>tel. +358 9 191 59502
>fax. +358 9 191 59498
>E-mail. pasi.laurinmaki at helsinki.fi
><<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>
>
>_______________________________________________
>3dem mailing list
>3dem at ncmir.ucsd.edu
>https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem

-- 
-Chen
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