1978 SHARP GF-9191..left output problem

[Daz 125]

another mint condition boombox but there's a problem..the preamp is working ok as both metre swing levels show normal output..it's when you turn the volume up on the left slider. the sound is very quiet and tiny..I've checked the left speaker and tweeter there's nothing wrong with them...it's the same if you plug headphones into it.. it's quiet on the left side..Ive checked all the switches and spray them with switch cleaner and nothing has made any difference...it was working OK when I first got it. but the sound faded on the left hand side as I was listening to the radio..it's got to be an amplifier problem. but I just don't know where to look. or what could be causing the problem..has anyone else had this issue..."I would appreciate it if someone could help me fix this.. and if possible point me to the component what has failed

 

[Eddy]

The first thing to check are the capacitors around the amplifier section.
I suspect they are bad . Don't know if you have a capacitor ESR tester?

 

[Daz 125]

The first thing to check are the capacitors around the amplifier section.
I suspect they are bad . Don't know if you have a capacitor ESR tester?

i did think about the caps.. thing is eddy the inside is mint condition..it doesn't look like its had much use..thing is i had a cap die on me before and the audio was totaly dead..this unit has sound but very low and tiny..do caps react differently

 

[Tinman]

Start with the easiest things first.
I'd clean ALL controls extremely well again starting with the volume.
Make sure to do one at a time spraying and working it NUMEROUS times back and forth (or up and down).
I've ripped into boxes before looking for troubles and finding out it was something simple like another cleaning.
All you need is one tiny little speck of dirt, dust, hair, etc. under one of those wipers and it won't work.
Just a suggestion.