John, do not replace the 100pF cap, C327, across T-207 with a ceramic cap. I
just went through doing that and after a great deal of advice, I used a
silver mica cap which solved the problem created by a ceramic cap in that
location. Tuned ckts of this sort require a high "Q" cap to function
properly...
73...Jordan VE6ZT
----- Original Message -----
From: "jkharvie via R-390" <[email protected]>
To: "Jim Whartenby" <[email protected]>; "R-390 Mailing List"
<[email protected]>; "Les Locklear" <[email protected]>
Sent: Thursday, June 27, 2024 2:44 PM
Subject: Re: [R-390] Update on R390A, open question regarding scope and
options fir lubrication
Hi Les,Long time no talk....
Jim - thanks for the information. I have used WD-40 for many years. It is an
interesting blend of materials that does a good job against oils and grease.
A tooth brush is what I used on the gears. Lubrication has multiple options.
I am not familiar with the Tuffoil engine oil treatment material.
Yes, both 10-turn mechanisms are among those that need to be lubricated,
best method I have found is to stair-step all the tabs at both ends of the
range, clean away the debris, apply a very light coating of thin oil to
front and back, work end to end to coat the tabs.
Would be interesting to have folks report back in how much torque is needed
to rotate the KC knob on their receiver, my guess within 3 sigma we are all
close.
I can say that prior to the {re}installation of the slug racks, but
following a substantial teardown and cleaning and re lubrication (all gears
removed, shafts, bushings, gears split, cleaned and teeth contact polished
where needed with 2000 silicon carbide wet dry paper on the surface plate),
each gear tooth was detailed deep clean, and used as lubrication a
multiply-alkylated cyclopentane (MAC) material, the receiver KC knob takes
very little torque to rotate. Add in the second phase of measurably reducing
electrical contact pressure by the application of NYE lubricants Inc. 760G
lube (only RF switch deck contacts completed thus far). I also applied the
760G to the trim cap central contact following a good cleaning by DEOXIT
with a cotton tip applicator swab under bright light.
If you consider the size of a #2 pencil as the diameter of contact lube
squeezed from the NYE source tube, I have used a total of about 0.1 linear
inch in precise application. My application method uses a 0.30" 4 inch long
stainless steel wire one end tapered and polished to a "point", the other
end with a 1/2 inch right angle bend so I can rotate the wire easily to a
desired angle. This stainless wire was re purposed from the "handle" of a
fast food carry out of a serving of hot rice.
Here is an in process picture of the cleaned gears and the 10 turn stack.
I am in the process of replacing the cap across the primary of T-207 with a
100pf, 3kV ceramic disk capacitor.
About completed with checking out the drift of the resistors in the RF deck,
looks like about 20% will be replaced. Caps appear to be in a better shape.
Will swap out those recommended.
Each day making progress...
thanks
John
On Wednesday, June 26, 2024, 12:55:11 PM EDT, Les Locklear
<[email protected]> wrote:
One particular area that is often overlooked...
The ten turn stops mechanism, thoroughly clean and lubricate liberally with
your synthetic oil of choice, thinner the better. If you've done the other
mentioned essentials, you can spin the KC knob almost like an SP-600!
Les Locklear
“Light travels faster than sound. This is why some people appear bright
until they speak.” – Steven Wright
----- Original Message -----
From: Jim Whartenby via R-390 <[email protected]>
Reply-To: Jim Whartenby <[email protected]>
To: R-390 Mailing List <[email protected]>
Sent: 6/26/2024 10:27:54 AM
Subject: Re: [R-390] Update on R390A, open question regarding scope and
options fir lubrication
________________________________________________________________________________
JohnI haven't seen a reply to your question so here it goes.
The few R-390As that I have had to remove the heavy application of grease,
I
have not bothered to disassemble everything. I have found that several
cleaning cycles using WD-40 as a solvent, your favorite detergent in
water, a
through water rinse, in this order, and a final alcohol rinse as a water
release agent will remove the most stubborn dirt and grease residue. Cycle
through different frequencies to expose dirty areas of the gears. An acid
brush on a dowel will get deep into the nooks and crannies during the
cleaning
process.
My favorite lube is Tuffoil engine oil treatment. I have been using the
same 8
oz bottle for over 20 years. It
doesn't take much to lube the R-390. I only lube the pivot points, not the
gear teeth which would attract dust and dirt. I use a long wood skewer
from the wife's
stash to get deep into the gearworks. Just a drop or less is all that is
needed. Over lubrication just leads to more problems down the line.
Don't forget to loosen and recenter the two bushings on the front panel
where the MC and KC shafts protrude. This makes a big difference by
removing the binding caused by misalignment.Regards,JimLogic: Method used
to arrive at the wrong conclusion, with confidence. Murphy
On Wednesday, June 19, 2024 at 11:43:06 AM CDT, jkharvie via R-390 <r-
[email protected]> wrote:
I am slowly making progress with my EAC R390A receiver. I have removed all
gears after preparation. I have inspected, cleaned, and prepared each
assembly element down to removing the cracked in debris found on a number
of
the gear teeth. I process each gear in sequence, one at a time, noting and
resolving any issues. Cam shaft bearings have been cleaned, both 10-turn
limits
have been cleaned, one was missing a brass washer between two steel stops,
made
a replacement. I have cleaned the top surface and bottom of the RF sub
chassis. The RF permeability cores were removed and carefully labeled and
stored to the side. Used about 500 cotton tip applicator swabs. Using
reprints
of manuals as guides.The RF cans have been unscrewed, indexed, cleaned,
contacts cleaned, components measured,.As I am moving ahead in the
cleaning
phase I have encountered a number of areas that should be lubricated (that
are
not on the list) and some that could be lubricated, that traditionally
were
not.
These frame out my question to the group.Among the open areas is some
thinking
that these receivers might benefit from a consideration of modern
materials
science and theories regarding measures to improve electrical switch
performance.
Key areas of reducing contact forces, reducing contact resistance,
eliminating oxidation, life-cycle etc.I got started by reviewing articles
that
appeared in April 1980 on the topic of using specific formulations of
lubrication on electrical switches and potentiometers.
From 2001 article written by an engineer with NYE lubricants Inc. (Now
foreign
owned)
https://www.machinedesign.com/mechanical-motion-systems/article/21816000/the-
right-lubricant-brings-out-the-best-in-electrical-switches
I am aware of the extent this receiver depends upon rotary multi-section
electrical switches. Many variable capacitor contacts as well. I am not
aware of any specific update to maintenance procedures to incorporate
contemporary electrical lubricants into the receiver baseline.
I am considering a product such as
https://www.nyelubricants.com/nyogel-760g
What say the group? Good for a subset, good for all? Why or why not?
I would be more than willing to try this stuff out and give some feedback.
Thoughts and thanks
John (N3JKE)
You
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