Re: SM4 WFD problem

Chris Walter (walter@cithe504.cithep.caltech.edu)
Tue, 29 Aug 1995 22:47:21 -0700 (PDT)

Hi Eric,

I assume from your message that this problem is happening for *every*
event where SM4 WFDs need to be read out. This means that problem is
not one card but rather is something common to the system(unless one
card is messing up the back plane somehow). The problem could be one
of several things.

First of all you should know that we have had problems with SM4
before. In that case the problem was with the backplane where a
capacitor was blown out and there was a line which could not hold its
voltage. I wasn't actually involved in fixing this problem so I hope
either Nat or Chris O will send more info. I think Mauritizio may
have helped to fix this problem so he can also give you some info and
maybe check if it is the same problem.

Another possibility is a problem with one of the VICs(the VME
interface modules) or the cables. Do we have the spare VICs yet? We
ordered 2 more. Before you start switching hardware around
however(something that can cause problems if you are not careful) a
good thing to check is the the long ribbon cable going into the VIC
modules. Take off the face plates at the far left side of the crate
and make sure the cable is seated properly in the VIC. It seems
somewhat unlikely to me that it could come unseated but maybe there
was a lot of stress on the cable or something. Check both ends of the
cable. There is another VIC module(configured differently) in the
system crate that the cable plugs into on the other side.

So to recap:

-Have Mauritizio if possible check the value of the voltages on the VME
backplane.

-If that is OK check that the cable is plugged in all the way on both
ends. If you unplug them make *sure* you plug them back in the right
way. They are labeled with an arrow pointing up.

You are probably going to need to learn how to use the WFD command
line interface to test things out to make sure they are working. I
hope Ed sends along instructions. With this program you can check
things without starting a run and do things like check one card at a
time. If we have to start doing things like swapping hardware this
will be very useful.

Keep us posted and continue to send to the wfd list.

-Chris