[Boatanchors] Contact cleaner and tube sockets?

[Barry H]

Hi Phil & list:

Four things I've picked up from the lists over the years:

1.  There have been reports of ionizing cleaners such as 409, Simple Green, etc. contaminating phenolic and ceramic sockets, switch wafers and insulators with the salt compounds they can leave behind if allowed to soak into such materials.  Often only part of the surfaces of these parts are water resistant, like the glossy sides of phenolic, but the eges are prone, which include the cutouts for switch contacts and tube socket pin terminals.  Ceramic wafers, insulators and sockets are often glazed, but not on all sides.  On the other hand, there are some who clean chassis by liberally spraying chassis, but then flushing with water (and even distilled water), then sun or oven baking the chassis.  I've never done that.  The downside results that have been reported include tales of actual arcing and sparking.

2. Deoxit is widely used and generally recommended for tube pins and sockets as well as switches.  If too liberally applied, it can cause phenolic switch wafers to swell up which can result in a binding switch if it's of a close fitting design (wafer to rotor).  This may often cure itself as the volatile component gradually wicks out and evaporates.  The most popular version -- D5 -- consists of only 5% conductivity enhancing/lubricant, the rest is cleaner and vehicle/propellent, etc.  The cleaning component is not of the ionizing type and evaporates away.  The 5% that's left behind as a protectant/lubricant is somewhat filmy and (I suspect) is unlikely to be left over in sufficient amounts and also unlikely to saturate the piece.  On balance, it's a good idea to use D5 to clean the pins and sockets, but even when using the spray can, I just put some on some small implement and apply the stuff to the socket pins -- or spray very sparingly and wipe up the overspray.

3. Tubes that won't oscillate.  A tube can test good on a typical tube tester, whether emissions or mutual tranconductance type, however fail to oscillate at the IF or whatever operating frequencies.  Tube testers -- even rather elaborate and nowadays expensive types -- use line frequency (60 Hz) or something like 3 or 5 kHz during quality tests.  There have been reports of tubes that will function at those low frequencies but not in the RF range.  That's one of the reasons the mil tester manuals caution that the only true check is to substitute a known good tube.  Another elusive problem is grid emissions.  Some testers have specific modes for testing this, however, I think (correct me if I'm wrong) the gas test on most should pick it up.  Otherwise a tube with high grid emissions will not show shorts and may test good for quality.

4.  An "accidental" extra component.  Solder connections that were originally good and still look shiny may have deteriorated internally due to impurities such as rosin that didn't completely boil off, "dissimilar metals", etc.  This has been known to form a variety of accidental components:  thermal breaker, resistor, capacitor, and even a diode.  These may not be obvious with an ohmmeter check.  Solution is to re-fresh all possibly relevant joints fully.  Also, there could be some problem with lead dress causing a parallel "gimmick" capacitor or maybe even a gimmick (twisted wires) that's not gimmicking right.

Hope some or any of this might help.  A fifth one -- DIP's -- Devilish Intermittent Problems.  This situation is best probed with one of the original instruments -- a pointed stick.  In this case, you'd power up and apply the tap test at various points on the chassis, listening for interesting sounds.

Barry






-- "Philip Atchley" <beaconeer at elite.net> wrote:
Hi, me again,
Two different people suggested that "maybe" the oscillator tube socket in
that NC-300 was bad, keeping the unit from oscillating.  I have heard of
contact cleaner's damaging and/or swelling the phenolic wafers of band
switches causing them to bind etc.

Here is an excerpt from one that I received from Garey, K4OAH that raises a
question.

"I guess I'd be suspicious of the tube socket.  I've been finding
more and more tube sockets that have been ruined by spray
"contact cleaners".  They become "leaky" between pins and screw
up all sorts of Hi-Z circuits."

QUESTION:   Can these cleaners also damage or "soak into" ceramic or
steatite band switches and tube sockets, causing leakage?  The reason I ask
is because both the bandswitch and tube socket in the NC-300 is
ceramic/steatite and look like they may be a little porous.   If that is
indeed the case, it would go a long way towards explaining why the set
refused to work even though all parts/wiring check good.

73 from the "Beaconeers Lair".
Phil, KO6BB

DX begins at the noise floor!
Merced, Central California
37.18N  120.29W  CM97sh

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