Adding SSB to the ARR-7 

			George Marshall W6BHR
			554 Westborne Drive
			Los Angeles, Cal. 90048 

  I bought an ARR-7 from R. E. Goodheart after trying in vain to find anything 
with that complete coverage and overall quality at anywhere near the price. 
Although Goodheart had already removed and bypassed the reradiation suppressor, 
this article on adding SSB will be written for those who have an unmodified receiver. 
For those already possessing one of these versatile sets, or for those contemplating 
purchase, the ARR-7 is an extremely simple receiver in which to install a product 
detector. 
  Proceeding directly to the heart of the matter, the following steps make it 
possible to modify the receiver in a few hours' time. First, remove and discard 
the 6AB7 which precedes the first of the two rf amplifiers. This tube was used 
only as a reradiation supressor so don't worry about losing gain or sensitivity 
in discarding it. The socket is utilized inthe modification and the tube is replaced 
by a 6SN7 Product Detector.
  The front-panel screws are loosened sufficiently to get an end wrench between 
the front panel and the chassis in order to remove the spst bfo switch. When the 
nut on the switch has been considerably loosened, the switch may he rotated about, 
so that with a gun-type iron, or other iron with a small tip, the connections may 
be removed from the terminals. Replace the old switch with a DPDT and reconnect 
the wires removed from the old switch in such fashion that they are switched ON 
in the bfo "ON" position. Use the uppermost terminals, the ones closest to the 
top of the receiver, for these connections, the single wire going to the center 
terminal and the pair of wires going to the other terminal. 
  Returning to the vicinity of the 6AB7 socket, there is a terminal board 
immediately adjacent, on which are mounted ·79, C80, R54 and R55. Clip off, or 
unsolder these components so the terminal board can be re-used. Be careful when 
removing R-55, as this 47K resistor can be re-used as the plate load for the 6SN7. 
The B lead in the lower corner should also be carefully unsoldered, then the entire 
board can be removed for ease in installing the new components which consist of 
a .1 mf capacitor, a 10K ½ w resistor, and the reinstalled 47K resistor. The terminal 
board is modified as follows: Removethe ground connection which runs in the vertical 
plane and swing it around to the B lug.
  While the terminal board is out of the way the octal socket may be rewired for the 
6SN7 as follows: Remove the antenna lead from pin 4 and the lead connected to pin 8. 
These two leads may now be directly connected by placing them on the unused lug of 
the terminal board when it is replaced. The jumper going from pin 3 to pin 5 is 
removed, carefully, fron pin 5 and connected to pin 6. If carefully removed, the 
ground lead connected to pins 1 and 2 can also be reused. A "soldering aid' tool 
is an asset for this sort of operation. A piece of spaghetti is slipped over this 
ground lead and it is then connected to pin 8 which takes care of the heater circuit. 
The other components are now connected to the socket, the 1OOK resistor from pin 1 
to pin 8, the 1OOK resistor with a 100 pf capacitor across it, from pin 4 to pin 8 
and a 680 ohm 1 w resistor from pin 6 to pin 8. (This is the only 1 w resistor; all 
others, are ½ w.) The terminal board can now be reinserted. 
  When placing the .1 mf capacitor on the terminal board, leave enough lead on the 
B end and it can be used to connect directly to pin 5 on the octal socket. 
  Remove the 3 screws from the bfo compartment and remove the cover. Inside you will 
notice a "gimmick," two wires twisted together; remove these and replace them with 
a 100 pf capacitor. Remove the lead going from the lug to the 6H6 for bfo injection. 
Remove the #6- 32 machine screw and place a ground lug un- der this screw and replace 
the screw. Replace the cover on the bfo. 
  Prepare a 7" piece of small coax or shielded lead as follows. Strip one end so 
that about ½" of shield is exposed and about ¾" of center conductor and its insulation. 
Strip off about ¼ of this insulation exposing the center conductor. This end of the 
shield Will be connected to the ground lug installed on the bfo compartment and the 
Centex conductor connected to the lug which formerly went to 6H6. The othex end of 
the center conductor is connected to pin 1 of the tube socket. The 47K resistor 
from,the terminal board can now be connected to pin 2 of the socket. 
  An 8½" piece of small coax is stripped in the same manner as the previous piece. 
With a hot iron, a place can be puddled and tinned with solder on the vertical wall 
of the bfo compartment nearest to pin 8 of the last if tube. The shield of the coax 
is grounded at this point and the exposed center conductor is connected through a 
10 pf capacitor to pin 8 of the last if tube. The center conductor at the other 
end is connected to pin 4 of the 6SN7.
  Now, on the opposite side of the receiver there is a long terminal board. On it, 
near the rear of the receiver, is the audio coupling capacitor C77; the lead nearest 
you is removed and transferred to a blank lug which is toward the rear of the receiver.
  Now strip 2 26" pieces of small coax exposing the shield and center conductor at 
both ends. Strip another 26" piece so that the shield and center conductor is exposed 
only on one end. This end will be connected to the DPDT switch at the front panel. 
An three shielded leads can be snaked up through the harness along the right side 
of the receiver when looking at the bottom of the receiver, which will tend to 
keep things neat. 
  The center conductor of the coax which is stripped on only one end is connected 
to pin 2 of the 6SN7. The center conductor at the other end is connected to the 
lug of the unused section of the DPDT bfo switch is closest to the center of the 
receiver. The center conductor of the next coax is connected to the center lug of 
the switch and the other end of the center conductor is connected to C77. The third 
coax center conductor is connected to the remaining lug on the switch, and thence 
connected to the point that C77 was removed from. 
  The 3 shields at the point near the switch are wrapped with bare wire and soldered 
together. The other end of the two leads going to the audio can be tacked together 
in similar fashion. Where the lead which goes to the Product Detector, goes by the 
bfo compartment, about ½" of shield should be exposed and conneted to the same point 
as the lead which went to the last if (the solder puddle at the side wall of the bfo compartment). 
  With all leads now installed on the 6SN7 socket, room can be found to connect 
the 10 mf decoupling capacitor to the ground lug of the adjacent tube. This completes 
the modification; plug in a 6SN7, hook up the power and start product detecting 
whenever the bfo is on. This modification does not affect ordinaTy CW reception, 
but makes it easy to tune and receive SSB signals. Either side band can be selected 
by adjustment of the bfo knob. It works like a charm ...   W6BHR