[Hallicrafters] Hallicrafters TO Keyer modification - Using it with a straight key

[Greg Mijal]

Hi:

Here's a good modification that allows the Hallicrafters HA-1 (TO Keyer) to be used with a staight key.  Hallicrafters did not build the TO keyer to use a staight key but I have a mod that will allow the user to run a staight key or bug thru the keyer with side tone and mercury relay action intact.

At V4A pin 2 (grid) of the 12AU7 attach a 47 k ohm resistor.  The free end of the resistor goes to the first terminal of the straight key.  The other terminal of the straight key goes to chassis ground of the keyer chassis.  I ran a length of RG 174 thru the phone jack at the rear to the key to complete the modification.  
The mod works great and you do not loose the electronic keyer action either.
73's
Greg
WA7LYO
Kinston NC