The most common trouble is a non-responsive channel in the DAS window - the power to this channel will usually be too high or too low and will not respond to changing the catie gain. The solution to this is to get someone at the observatory to press the “FPGA reset” button on the appropriate tied array unit in the screened room. Each press resets the timing of the tied array link, and this may fix the problem. The timing will come back randomly however, so it may take more than one press to fix it. Each of the four channels on the tied array boxes has a set of LEDs above the FPGA reset buttons, and the channel that isn't working is usually obvious as its LEDs will look different to the others, and the FPGA reset buttons should be pressed until the LEDs match the expectation.
You may find that after reprogramming that several baselines in a particular IF won't give fringes. These may or may not be common to one antenna. The solution to this problem is to reprogram the blocks that are used to make the zooms, which by default are block 7 for IF1 and block 27 for IF2. Simply go into the Edit window in cacor, type
prog 7 27 and wait for them to successfully reprogram, then exit the Edit window and reissue the
calband 3,4 command in cacor. This usually fixes this problem, but may need to be repeated a couple of times.
If cacorr reports “Block #N detached” (usallt 7 or 27) you need to force it to reload.
* stop caobs * In a terminal
select most defaults, choosing (for example) block 27 then “.system.reboot”
* ping the bcc (e.g. l-bcc27) until about 10 responses
> Click Edit > block > 27 (for example) > remove > install > <enter> > prog 27 > calband 3 4 (in tkcorr)