[evlatests] More notes from April 11

[Jim Jackson]

Antenna 13 - Mike just made me a set of plots from 13's deformatters while 
the antenna was in x-band.  The IF-D plot shows what appears to be the 
normal response for the Sampler and DTS but shows a lack of the normal 
small spurious signals we see in the other three IF's.  Also, Barry 
mentions seeing little effect when changing attenuator settings.  The last 
time I saw behavior like this, a power cycle of the T304/T305 was required 
to fix it.  I will have someone do this and check things out tomorrow.

Antenna 14 is showing some occasional misbehavior in two DTS modules - IF'C 
went away for Barry, IF-B has logged parity errors on the optical 
link.  Jerry and Leon reset clock levels into the L302 yesterday but did 
not recheck levels into the DTS and other modules.  If DTS clocks are low 
by a similar amount it could cause occasional erratic behavior in these 
modules. Tomorrow, someone will recheck and set all levels from the new 
L305 to the other modules in Antenna 14.

Antenna 16 - The issue with the L302's occasionally getting into this bad 
state is known and hopefully will be taken care of by the new firmware.  It 
seems to happen when the MIB loses control of one of the DDS chips - 
apparently the control loop device in Barry's case today. For some reason 
the module does not go into standby when this happens.  Usually, one MIB 
reboot fixes it but on rare occasions additional MIB rebooting or a power 
cycle is required. This is the same state I found one of Antenna 14's 
L302's in the other day.

Antenna 18 - We will look for a possible cabling problem in IF-C.  The FFT 
plot from the Deformatter shows ripple that could potentially be caused by 
a connector or cable issue. Since we turned this antenna on, I have seen a 
few comments that IF-C is not as good as IF-A.

Jim




At 03:48 PM 4/11/2006, Barry Clark wrote:
>Lack of fringes on IF B, all EVLA antennas turned out to be an unlocked
>Fluke synthesizer on the VLA side (noticed by op JC Campbell).
>With that taken care of, 13 B is present and strong.  13 D is still about
>a factor of 10 low in fringe power.  (The link is being overdriven at
>most bands for 13 D, but when I twiddled the attenautors, it did not much
>change the fringe power.)
>
>Shortly after noticing the Fluke problem, we went off to a set of
>spectral line observations by Vivek.  This should quickly tell us if
>I have set up 13 D on the wrong lobe of the delay function (I don't
>think so, but maybe).  When we started his file, 14 C went away.
>Resyncing the formatter (at about 21:05) brought it back.
>
>Lack of fringes on 16 A and C appears to be an L302 problem.  It
>rather persistently refused to lock.  I tried various frequencies and
>could get it to lock at none.  I rebooted it.  After fairly normally
>refusing to lock for a few minutes, it got itself to the state I believe
>to be impossible:
>M_LOCK=1, C_LOCK=0, STANDBY=0
>I rebooted it again.  After the second reboot (about 21:35), it actually
>locked.  Finally, all IFs present and (except for 13 D) accounted for.
>
>I rather suspect that Ken is so used to this sort of shenanigans that he
>would have taken care of all of it in the first hour and not bothered to
>mention it.  But when he isn't present, the system does seem rather fragile.
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