Hello JukeBob,
Welcome to the forum.
If the amplifier is the original and the jukebox is still fitted with an output package? This should be in the amplifier compartment, it is 25cm x 11cm or 10 inches x 4.5 inches approx, it has E1 to E7 connections Left & Right.
You should find that there are a number of cables attached to these tappings, the jukebox speakers are usually connected as follows:-
Black (common) E1 Right
Violet (left channel) E6 Left
Pink (right channel) E6 Right
Red (left channel Wall Box/extension speaker) E4 left
Brown (right channel Wall Box/extension speaker) E4 Right
To balance any extension speakers you can increase the extension speaker tapping connections or reduce the jukebox speaker tappings.
Regards
Alan
Alan Hood
ami-man
UK