and more..

> Recently, while troubleshooting a faulty mass 2/3 beam display,
> we changed the original OPA-104 chip in socket IC-2 on the low
> mass head amplifier for an equivalent replacement OPA-128 chip
> obtained from Pro-Vac Services here in the UK.  Since then, we
> have had excellent SLAP data around the expected -428 value!
> VSMOW continues to analyse near to zero so that we no longer
> have to apply a significant "stretch" correction for all our
> Deuterium data.

I took over the running of a SIRA II, my first device. The machine
had had a difficult history. For no reason at all, that I could see, the
HT would jump a couple of hundred volts and so the run would be
aborted... bad news... and the machice kept on going, not so good
for over night runs. This went on for ages and I was getting no
where replacing chips... it was really upsetting but something I was
learning to live with...

then one friday night there was a flood in the room above the mass
spec suite... and the SIRA got a bit damp. So I got Dave Smith from
ProVac to have a look and give it a service. In the course of the
week I mentioned this problem to him. Down he gets, pulls out one
of the boards, removes a chip... did not replace it! puts it back
together and....

never had the problem again.

or it just needed a bit of a soaking...

In the end I really liked it but boy at the beginning...


Andrew J.

Dr A.M.Johnston
Scottish Crop Research Institute

Tel No: (44) 1382 562731 ext 3732
Fax No: (44) 1382 562426