Date: Thu, 4 Nov 93 09:50:18 EST
Subject: Re: SX50 User group
From: "Neil S. Summer"

In message <9310131821.AA02286@ice.geology.wisc.edu> writes:
> Neil: Thanks for the tip. I've sent it along to those I have on an
> evergroing email list. Next week or so Dave Pierce should be mailing out a
> questionaire to all those on the official Cameca users list (we have only
> email addresses for a quarter or third or so). Have you done the ground
> test? If so, maybe it would be helpful to describe the procedure.
> Apparently something to do with using a Whetstrone Bridge between apparent
> ground and ground ground; we haven't done it (we have a heavy ground wire
> that I've been told is grounded somewhere in the basement, but I guess I
> should check it!) Also, I keep a daily temp and humidity log (Fisher sells
> a relatives cheap, ~$25, temp/hygrometer). Where was the discharge? Power
> supply?
>
Hi john,
Took a while to get back to my outstanding mail...

1) Please add John Shervais to your email chain
(Shervais@epoch.geol.scarolina.edu).

2) The corona discharge which cascaded through our boards, blowing chips (but
not fuses) started in our vacuum power supply. The logic board from that power
supply was sent up to Sam at Cameca ( I am trying to save money by sending them
the boards for repair). Our major problems lay in these boards (in descending
order): vacuum power logic, vacuum logic, Ion pump power supply, HV CRT#1,
video1 & 2 and Numeric 1.

3) An Aside: A cooling water junction exists inside the large cabinet above the
main and monitor power supplies. With high humidity, the temperature
differential between room air and cooling water can lead to condensation on the
hose and droplets of water directly into these power supply units.

SO: a) Keep humidity below 60%
b) have only a 10 degree differential between room air and cooling water
temp.
c) Run your hands under eposed cooling water pipe to check for condensation.

4) We will have a single instrument ground fitted (with ground rods) and an
independant cooling system. In addition we have two dehumidifying units to kick
in when humidity reaches 60%. I did not do a test but saw the electrician assess
the resistance between the ground and the SX50 chassis.

All the best,
Neil


Neil S. Summer
Department of Geological Sciences,
University of South Carolina,
Columbia, SC 29208

TEL (803) 777-6300
FAX (803) 777-6610

Summer@probe.geol.scarolina.edu