In article et,
Nicholas O. Lindan wrote:


By Ole Occam's razor, and a description of the problem - 'it works
till I touch the knob' - my first guess is a dirty and/or worn
synch selection switch or trigger level pot. The pot wouldn't
happen to have one section for Ch. A and one for B and get
bypassed in Auto, would it?

If it were mine, I would first try a spritz of contact cleaner into
the switch via the front panel slot (IIR465C). All contact
cleaners are the same - mineral oil and alcohol - so the cheapest
Radio Shack stuff works as well as anything. WD40 also works well.

Ugh. and Ugh again.

I'd raise three cautions about this advice:

[1] My recollection is that Tek specifically warns against using
most contact cleaners on, or around, certain of the internal
controls (e.g. the attenuator switches). These switches are
apparently quite sensitive to contamination, as they deal with
high-impedance signals. Spraying an oil-and-alcohol contact
cleaner anywhere in their area might very well contaminate them.

IIRC, Tek's recommendation is to use pure isopropyl alcohol, and
a small clean brush, for cleaning contacts.

[2] Not all contact cleaners are the same. Many used for sensitive
equipment are "zero-residue" types - they have a cleaning solvent
and propellant, but do not contain any sort of lubricant, and are
intended to leave nothing behind on the contacts. Even among the
contact treatments which do contain a lubricant of some sort, there
is wide variation in the type of solvent used (some use alcohol,
some use a hydrocarbon or chlorinated/fluorinated hydrocarbon)
and the lubricant used (some use mineral oil, some a polyphenyl
ether, others something else entirely). It pays to use the right
combination for the job.

[3] I would not use WD-40 as a contact cleaner, on anything less robust
than an electric motor. It's not formulated for that purpose
(in fact, it's not really formulated as a long-term lubricant!)
and it is notorious for getting gummy and attracting dust over
the long run.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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