[SignalOne] CX-11A repairs

[Bob Swaine]

Hello to all,

 

I just completed the repairs required to have my three CX-11A's 100% back
among the living. My first radio was apparently hit by a power line surge
years ago and stored away. The second radio was purchased knowing that the
finals were blown, but not knowing that just about every board had been
"tinkered" with, and not in a good way! The third was basically working, but
needed deep cleaning, PTO repair, and full alignment.

 

I wanted to pass along a few of the findings that I learned the hard way:

 

-         Do study the manual - having the original and the annotated manual
from Bill Turini's Signal One web site is a must!

-         Double check what you are looking at against the manuals, you will
find production changes, Paul Kollar's updates, and the occasional mistake
in the manual (not to mention just plain wrong parts in place).

-         Do take the time to pull data sheets from the internet for any
parts that you may suspect are a problem. The data sheets will often add to
the limited info from the manuals.

-         Take the time to perform any needed updates from Paul Kollar's
list once you have the radio working.

-         Depending on the radio, some of the tantalum caps were right on
the edge voltage wise, and should be replaced with the next higher voltage
rating. Also, I found shorted tantalums in two of my radios.

 

Couple of things to look out for:

 

-The PTO's are not directly interchangeable - the varactor diode CR1 is
reversed in the B PTO - not a fun repair, as someone had swapped them in
radio #2.

 

Two of my radios had an annoying hum in the rx audio that was attributed to
the + and - 15volt lines, the fix was to remove the A3 power board and the
A37 motherboard to get to the A21 power filter board, and then clean and
tighten the cap screws, board mounting screws, and transformer ground
connection - cleared up the noise.

 

Sorry about the long note, but these are great radios when they are working
properly - actually hears signals that my Icom 7700 struggles with.

 

Bob K7AAE