[R-390] Update on R390A, open question regarding scope and options fir lubrication

[Dan Martin]

It’s always great to see the R-390 mail list flicker to life again every now and then.

Seems a lot quieter these days. Les is “semi-retired”, Chuck moved on from his awesome 390A work when finding parts became tenuous, we are all older.

I still have my beautiful ‘67 EAC that was thoroughly “Ripple-ized in his shop over a weekend spent together so many years back. I swapped him a really nice TV-2C for his attention.  The EAC rests in a new CY-979A cabinet - and where did Mac find those years ago?

Dan
WB4GRA

Sent from my iPhone

> On Jun 27, 2024, at 7:35 PM, David Wise <d44617665 at hotmail.com> wrote:
> Discussion about two months ago: For high-Q tuned circuits, mica is still the king, don't substitute ceramic especially Type II.
> 
> Back when I was sorting my R390A, I warmed the IF deck with B+ applied.  Next morning a couple of the color-striped Sprague "Prokar" caps (plastic-impregnated paper) had shorted.  They had measured great for leakage when cold.
> 
> Dave Wise
> SWL (inactive)
> ________________________________
> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of jkharvie via R-390 <r-390 at mailman.qth.net>
> Sent: Thursday, June 27, 2024 1:44 PM
> To: Jim Whartenby <old_radio at aol.com>; R-390 Mailing List <r-390 at mailman.qth.net>; Les Locklear <leslocklear at hotmail.com>
> 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 t