F61 = Check speaker connections. If this doesn't help contact dealer.
http://www.manualslib.com/manual/760927/Panasonic-Sc-Pt750.html?page=33
See also
http://www.justanswer.com/electronics/4i8vd-sc-pt750-comes-f61-error-code-sites-suggest.html#re.v/175/
You could also, on the basis of nothing to loose, open up th eunit and check for bulging capacitoirs and replace.
X
July 2015