[SignalOne] Case On

[jerry]

So - A care package arrived this morning from K5OG - an LM380 amplifier 
card.  Thanks Fred!
It's working now, and the radio is IN ITS CABINET!

Instead of messing with standoffs, I
* Covered the bottom of the amplifier card with 4 layers of Kapton tape.
* Soldered pigtails to the ground plane on top of the  scalped power 
supply board
* Put the amplifer card on the pigtails and soldered it to them.

...So essentially, that amplifier card is soldered to the PS card.

I replaced the nice Signal/One pins on the amp card with Dupont headers. 
  And carefully put the Signal/One pins in a baggie which
I added to my growing stash of CX7 parts.

Fred, where did you get those pins?!?  Got a source?  A part number?  I 
read somewhere that they were made by AMP.  Sure would like
to buy some spares.  What with all the board shuffling, they 
occasionally break off.  I've been soldering a wire inside them, and 
then
sticking the pin & wire back in the board hole and soldering.

The amp works fine.  There is some hum.  Some in the amp, mostly coming 
from the rest of the radio.  Is that just how they are?

I find hum in tube equipment is often due to ground loops.  You have a 
tube filament or filaments, and the manufacturer has neglected
to indulge in return wires for the filament current.  So the return 
current goes through the chassis, creating AC voltage drops, which
low-level audio amps dutifully amplify.  I learned about this the hard 
way, when somebody gave me an oscilloscope in high school.  It
showed a hum trace, which disappeared if you shorted out the input.  
Heathkit.  Aluminum chassis held together by self-tapping sheetmetal
screws.  Worked great for 10 years or so, and then dissimilar metal 
corrosion at the screws...

Getting the case back on proved to be a bit of an adventure.  It was 
almost on, and it got stuck.  Wouldn't move.  Was there a wire pinched
that was going to break if I insisted?  Nah, it was the lower PA 
cabinet.  I had totally forgotten that the screws for that go through
the case.  Had to finagle the thing back off and remove all those 
screws.

   The case came to me with one missing ( actually destroyed ) rear foot. 
  I had some rubber equipment feet, but they were too tall.  So I
cut one down on the lathe.

   There are several screws that have "graduated" to the next size.  
Always happens with aluminum chassis & self-tapping sheetmetal screws 
:(.

SO - I now have a reasonably functional CX7A.  Almost everything works.  
The antivox is not connected, so I expect that VOX will not work
very well.  There's a bit of hum, but it's drowned out by ordinary band 
noise.  Receive is sensitive, the calibrator is twenty over nine.
Full power transmit.  The "broadband" works.  The CW keyer works.

   The radio definitely sounds happier with the RF gain down.  The band 
noise seems to recede, and the voices get smoother.

   The case is chipped in the front - at the usual places.  Corners & 
edges.  Let's see about touching it up.    I got out my "Color Muse 2",
which is a colorimeter that connects to a phone or tablet via bluetooth. 
  According to the Color Muse 2,  It's "Eggshell" gloss.  The closest
match is Sherwin-Williams SW9580 "Cracked Pepper".  Then Valspar 6011-2 
"Burnt Tile".  Then PPG1005-7 "Dark Granite".  Then Valspar 1011-10 
"Brown Velvet".

   I found a website that sells touchup paints to match S-W colors:

https://www.myperfectcolor.com/paint/498122-sherwin-williams-sw9580-cracked-pepper/spray-oem-bottles-and-pens/paint-pens/low-lustre

The pens don't cost much, but there is a "batch production fee" of $30.  
So - is it worth $40 to me to have a nicely touched up cabinet?  
Maybe....

                   - Jerry, KF6VB