[R-390] White lines on knobs and more

[John Gedde]

Hi Larry,

It looks great!  I have moved away from using a spray primer on aluminum prior to paint in favor of a chromate conversion coating.  Loctite Bonderite is what I use.  It's what we use at work for spaceborne mechanisms that get painted or aluminum surfaces that remain bare (non-anodized).  I've never had any issues with adhesion using this stuff.  Basically you clean and deoxidize the aluminum, dip it in Bonderite for a minute or so, rinse and let dry.  The aluminum turns a golden color and paint readily adheres to it if you spray within 24 hours.  The coating is also known by other names: ChemFilm, Alodyne, Iridite, etc.

John

-----Original Message-----
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> On Behalf Of Larry H
Sent: Friday, September 6, 2019 7:02 AM
To: R-390 Forum <r-390 at mailman.qth.net>
Subject: Re: [R-390] White lines on knobs and more

Here's the update promised, and a pic is attached.  The knobs are done.
The white lines sure do go on a lot easier when the black paint is cured.
The wrinkling of the black paint was solved by using a good self etching primer.  Thanks for the tip.

I've been busy on some other boring stuff, but the R-390A has been getting a little attention.  The calibrator would not adjust to WWV, so determined that the 200 kh crystal was oscillating a little too low.  Got a good one so that is fixed.  That allowed me to adjust the EP on the VFO a little easier, so it is now +/- 100 cycles.  As part of that procedure, I adjusted the linearity stack so that it is much better than it was.  Before, it was
+/- 1.9 kh, now it is +/- 0.2 kh at the 100 kh points.  I don't know if 
+I'm
going to try to improve that or not.  I also went through all the crystals and installed about 8 different ones to get the band deviation down to under 0.3 kh variance on the popular bands and under 0.7 kh on the rest.
In the process I took a few apart and cleaned them to get crystals that were close enough to their correct frequency.  That was fun.  The power on micro switch was not working intermittently.  Luckily, it only needed a little adjustment on it's mounting bracket.  I did a quicky drift test, and after it warms up for 20 minutes it's pretty good, + 300 cycles during warm up.  After that, it's quite stable.  Right now, I think it is in good enough condition to go through the alignment again and see what we get.
>From the use I've had of it up to now, the sensitivity seems good, although I've not measured it.

Regards, Larry

On Fri, Aug 16, 2019 at 10:03 PM Larry H <larry41gm at gmail.com> wrote:

> Well, I finally got all of the knobs finished, except for one.  It's 
> being a pain getting the black on it without wrinkles.  Tried a couple 
> different metal primers to no avail, and they are supposed to be good for aluminum.
> Any suggestions?
>
> Here's a picture of my progress.
>
> I'm now working on the BFO stability.  It currently is drifting down 
> about
> 150 cycles in about 1.5 hours.  This is fairly common for one of this 
> age, but is not good for CW or SSB reception or some alignment 
> procedures.  You can see my counter probe attached to the BFO output 
> at the front left.  I'm going to try to get it down to less that 30 in .5 hour.
>
> Happy fixing.  Regards, Larry
>