Harry we are all keen to help, but Super is right on the money here.
Some further diagnostics are needed first.
Is there any audio of any description from the Right channel....hum, buzz, etc.
Is the issue on all inputs, radio, tape, line in?
Are you sure the speaker you are testing the channel with is working?
Have you tested the line out from this channel, if this unit has it?
Can you try to obtain headphones or any adaptor plug to convert the jack?
Why did you take this box to a tech for an opinion....do you want to fix it yourself and is that within your skill level?
Just a few initial friendly questions.