[Amps] Vacuum relay adjustment?

[N3XX]

Hope someone on the list can help with information about a vacuum relay I 
have.  I'm working on getting an LK-800 amp back in good working condition, 
and one of the problems it has is a T/R vacuum relay that won't go back to 
receive after transmitting.  If I tap on the relay, it does go back to 
receive.  The relay is a Jennings RJ1A-26S.  On this relay is a screw that 
looks as if it is for adjustment, but I don't know what it adjusts.  I'm 
guessing it has to be either contact spacing or spring tension.  I hope it's 
for spring tension, and by adjusting this screw I can put a little more 
tension on the spring, and it will return to receive when finished 
transmitting.
Just thought I would check here and see if someone knows what the screw is 
for before I start turning it, not knowing what it is supposed to do.
Thanks for any info.

73,
Tim - N3XX