[Hammarlund] SP-600 panel inspection

[Al Parker]

Hi SP-600 aficionados, et al,
    A good  friend, Tom, W4PG, has recently completed a long, painstaking,
and very detailed restoration of an R-390A, and while he's working on an
SX-43 in the meantime, he has bought an SP-600 for his next project.  He's
been collecting info, tips, parts, etc., in preparation, as well as doing
inspection work.  He sent me his analysis of the SP-600 panel construction
a week or so ago, and suggested posting it to this reflector. He has also
allowed me to put it on The Hammarlund Historian website, where it will
appear very soon.
http://www.hammarlund.info

    I will relay any pertinent discussion/comments to him.
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info

=============================================
The following discussion was offered for our edification by Tom, W4PG, and
is presented with his approval, with very little editing:

  I've finally started disassembling the SP-600-JX26, S/N 128XX,  in
preparation for restoration.  The point of this e-mail is the method that
Hammarlund used to do the lettering on the panel.  First, they etched (not
stamped as the R-390A panels) the lettering into the aluminum.  The
lettering is relatively shallow in the panel and it shows typical etch
pitting inside the letter, but not outside.  Further, there is no small
berm on the edge of the lettering as would be if it were stamped.  (The
action of the stamp is to push metal to the side of the letter causing a
minor berm that is distinguishable).  Then they use a  waxy paint pencil
to fill in the lettering.  After that they apply a (more or less) clear
coating on top of the whole panel.

Why do I think that is an accurate description?

1.  I used rubbing alcohol to clean one letter around one of the controls,
and the white lettering disappeared on me.  Conclusion, they used a waxy
paint pencil rather that enamel paint to fill in the letters.

2.  I had what appeared to lots of nicotine stains on the panel (certainly
possible).  I cleaned part of the panel while it was still installed and
found that the underlying gray paint was a very light color, with the
darker (normal) color provided by what appeared to be nicotine, but now I
believe the "clear" overcoat.

3.  When I pulled the panel, the areas beneath the knobs very definitely
had an overcoat of "clear" material because there were definite
demarcations between the areas under the knobs and outside the knob areas.
The edges of those areas were ragged due to wear and the coating showed up
in an obvious manner.

4.  I washed the panel with soap and water, and can now see that any area
that had been protected by knobs, ID tags, or the meter edge showed that
underlying clear coating.  So Hammarlund, in some manner, chose a poorer
method of doing the lettering than Collins in the 390A series. Kudos to
Hammarlund for the etched lettering (though shallower than Collins and
thus a bit harder to re-letter), but shame on Hammarlund for the waxy
paint and the (50 years later, not-so) "clear" overcoating.

Note:  Al, I know I pointed this out to you  --  Even though my SP-600
took
a pretty heavy hit to the front panel up around the XTAL frequency
control, nothing appears to be broken inside the XTAL unit.  The black
bezels around the dials are a bit bent and interestingly enough the little
dial announcing the frequency band is bent a bit and the coupling on the
XTAL freq switch is bent a bit, and the windows in the black bezels are
split, but other than that, no major damage.  This project will take lots
of time, but I think this old Super-Pro will be back in great health in
about a year (at my very slow pace).

Best,
Tom, W4PG
May, 2004