During the ongoing shutdown, there has been considerable work on DIS electronics and mechanics. I attach below FYI some excerpts from R. Lucinio's trip report and from a report by Gordon Richards. Ed Turner +++++++++++ DIS: The LN2 fill Forth code was rewritten in order to simplify the time counter interrupt routine and allow for the generation of code to querry the system for information on previous fill cycles for the purpose of monitoring LN2 fill operations and to set or modify the several time constants involved in the auto-fill system. The new LN2 fill code was run and all fill operations were verified. Note: The Forth command ".LN2", in addition to previous information, now returns data regarding the previous fill operation, including elapsed time since the prior fill, conditions triggering the fill sequence, fill times for each camera, etc. In addition, there is now a new word, "*LN2" which returns all of the data given by ".LN2" but without the verbiage, just a series of ASCII values for computer digestion. Fiber optic converters for camera control and data aquisition were designed, built and installed on the DIS Mirella PC camera interface board. Proper operation was verified and circuit changes were documented, Jon Brinkman receiving copies of all new DIS Forth code and circuit schematics. Addendum 24 July 98 Other DIS problems addressed were : Following a report of data aqusition problems, Jon Brinkman and I examened the test data and saw two problems, one affecting the red camera and one affecting both cameras. We felt that the red camera problem was most likely due to a hot bit probably in the A to D converter. I changed the converter and Jon ran several test frames which seemed to be free of that problem. Upon 'scoping the serial clock and data lines, common to both cameras, we discovered extranious data bits being picked up on the serial data line. Switching to the last available MAI fiber converter cleared up the symptoms. Subsequently the MAI converters were abondoned for the on board converters installed as described above. Data tests run look proper with none of the prior problems. There were also a couple of robotics problems involving the grating turret and its detent. the detent out limit switch needed an adjustment and I re- defined two of the turret positions, Mirrors and Gratings2 by 1 and 2 steps respectively. The robotics were exercised in three orientations of the instrument and all operations performed without error. RFL ++++++++++++ I just got done looking at the bias frames that John Brinkman took with DIS using the new A/D converter. If you want to look at the plot, it is in /home/visitor1/gordonr/dis/biashist16July98.ps The RN on the red side is now down to about 7.6 ADU (14.9 electrons), though it would be nice to get a few more bias frames to get a better measurement of this. So, congratulations on the fix. Thanks! On a similar note, I showed Connie the plots and she noted that the plot of the blue histogram might be showing that plateau as a result of the 16 bit flapping around (since the spread is about 16 counts). Thus it is quite likely that the blue A/D converter needs to be replaced as well, since there may be a similar problem (albeit a smaller one) with the A/D converter on the blue side. Gordon APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 62 in the apo35-dis archive. You can find APO the archive on http://www.astro.princeton.edu/APO/apo35-dis/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-dis@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO