Hello and welcome to the forum.
If you are in the UK then I suggest that you contact me, we can sort out any issue with your 1981 Rowe Ami R-85 Starlight, you may have called me already, I am sure I spoke to someone last week or this week who had just bought one off of Ebay.
The (MHG/Kunick) Rainbow MK4 amplifier was a poor substitute. MHG who had the UK Rowe Ami distributorship at the time; bought the jukeboxes from Rowe Ami less the amplifier and output package.
Before you start looking at the jukebox speakers I suggest that you disconnect the jukebox speakers from the amplifier or output package and try some extension speakers to see if it is the amplifier that is at fault.
Regards
Alan
Alan Hood (ami-man)
Games Unlimited & Datex Systems
Units 4 & 5 Lion Park
New Street
Halfway
Sheffield
S20 3GH
UK
0114 247 0242 phone
alan-hood@datex.co.uk