The discussion about contact cleaner isn't altogether mundane.

I worked at Tek for many years, although I'm certainly not a guru when
it comes to oscilloscope maintenance. But I do recall one experience
with cleaning solvents and board-mounted switches.

Before introducing a new instrument, we went through a lengthy process
of building and testing prototypes, which I described some time ago in
this newsgroup. In one group, it was our practice to borrow some
assemblers from production to build the prototypes. One afternoon I was
looking at some units they had built, after they had left for the day,
and saw that the plastic of some switch bodies was very badly crazed --
they were covered with tiny cracks. Some experiments with bottles of
solvent we found in some of the assemblers' work areas pinned it down to
one particular liquid. The problem was one of the ingredients, which was
a relatively common solvent of the time. Unfortunately, I don't recall
which one -- it was something pretty mild as solvents go, like toluene
or Freon, not a relatively strong solvent like acetone, which we all
knew better than to use. We found out that the solvent had been banned
from production, but the assemblers kept a supply out of sight because
it was really good at removing flux.

The lesson is that even some normally pretty innocent solvents can
destroy some plastics. Other components can also be ruined by various
solvents, so that's another reason to use some caution. As just one
example, it was found that Freon and its relatives would migrate up the
leads and into even pretty well sealed radial leaded aluminum
electrolytic capacitors, corroding the insides and causing premature
failure. This was solved by improving the end seals, but only after a
lot of the older type reached the field, some on boards having been
washed with Freon. Of course, Freon is no longer used, but there are a
host of other potential problems. It's ultimately up to you to decide
whether you want to experiment with your scope.

As for WD-40, I love the stuff and use it on all kinds of switches and
electrical components. But I mentioned a short while ago that the cam
switches in the 465 and some other scopes use PC board pads for
contacts, and when the pad's gold plating is gone, the switch -- and the
scope -- is dead. So it doesn't seem like a good thing to me to use a
cleaner on those that'll leave a film which can collect dust or anything
abrasive.

I don't agree that a switch's ability to withstand WD-40 or any other
particular chemical is an indicator of its quality. But we all have our
own criteria we use to judge.

Roy Lewallen, W7EL

John Miles wrote:

You know, it's funny how often these debates flare up over a subject as
mundane as contact cleaner. "My tuner cleaner is better than your tuner
cleaner. Your tuner cleaner should be used only in Ukrainian opposition
candidates' minestrone. My tuner cleaner costs more than HP printer
ink. If you spray your tuner cleaner on a Tektronix 465, it will
trigger a resonance cascade and gate in alien overlords from the planet
Xen." Yadda, yadda, yadda.

Despite all the gurus out there forking the evil eye at WD-40, I sure
seem to own a lot of stuff that still works fine after being sprayed
with WD-40 over the years (decades, in some cases). Yeah, I know.
"Data: n, plural of 'anecdote'."

Some of these gurus are admittedly respected veterans of companies such
as Tektronix, with whom mere mortals are loath to argue. All I can say
is, those switches must not have been of the greatest quality in the
first place, or the gurus wouldn't have to spend so much of their time
on Usenet warning people against hosing them down with WD-40.

Just sayin', is all. No disrespect intended.

-- jm

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