[Elecraft] Foot Switch Doesn't Work

[kg6mzs]

Hello All,

I've connected a Heil foot switch to to rear panel PTT In RCA jack and 
it doesn't key my K3.

I searched the archives here  and found that Don W3FPR had suggested 
testing the foot switch of another unfortunate, Dick K9OM, who suffered 
the same problem.  This thread went unresolved, AFAICT.

I've tested the Heil and it checks out.

Any ideas as to why my foot switch will not key the K3?

TIA,

Eric

KG6MZS