Hi all, I just picked up a Viking 2 last week that's in beautiful condition . It has very little grid current 2 mills until I turn the drive to 9. Than there is 7/8 mils of current. There are mods instead of 6au6's there are 12ax7's driving a 6cl6. , 807's to 6146 . I made a mistake trying to tune and had the drive to far and plate current and took out the 5v4ca rectifer . This is mated to a HRO 50t ,also the Viking has a trans relay the coax to the back of the case and one that plugs into the two small holes at the bottom. This is my first AM transmitter and I don't want destroy it.
This is a common problem with both older Heathkit and EF Johnson transmitters.
The modification is as follows:
1). Replace the 25k 4W potentiometer with a 25k, 5 Watt unit.
2). Add a 10k to 15k, 10W series resistor between LV B+ and the Drive Potentiometer
3) Add a 22 uF, 450 Volt electrolytic at the junction of the drive potentiometer and the New 10k to 15k, 10W resistor.
Below is the Buffer-Driver Stage modification schematic: