[Elecraft] K2/100 Keying a Drake L-4B

[Ariel Jacala]

Hi Elecrafters,
I am ready to key my Drake L-4B using my K2/100 but I read from a previous post:
"If you already have the KPA100, look on the rear panel and you will see an RCA jack marked "PA KEY OUT" between the ground connection and the power connector - this will allow you to key your external amplifier directly - but only if your amplifier has a positive voltage for its keying line.  If  your amplifier uses a negative voltage keying circuit (like the Collins 30L-1 and some others) you will need to construct an external circuit to key the amp.  73 --don n4hh K2/100 #2028 "
Does the Drake use a negative voltage for the keying (line)?
If it does what modification do I need.   I installed the Soft-key mod made by Harbach. I am not sure whether that converts the Drake to positive voltage keying.
Any help is appreciated.
Ariel