70 MGB GT - Tachometer Woes

[Gary Davis <GDAVIS@ibr6gw80.gp.usbr.gov>]

One of the plugs on the back of my tach is loose and causes the tach to
sporadically work and die depending on the "bumpiness" of the road. 
The loose plug is the uppermost male (on the tach) plug near the outside
edge of the unit.  What must be done (and how do you do it?) to the
plug/wire connection so that my tach will operate correctly on bumpy
roads?

TIA - Gary Davis