Somewhat cryptically from the service manual I found in less than a minute with a Google search:
"F61 The abnormalities in an output or power supply circuit of POWER AMP: In normal operation, when DCDET2 goes
to "L" (Low) (Not during POWER OFF condition), F61 appears on FLDisplay for 1 second and PCONT goes to "L" (Low).This is due to speaker output has DC voltage or fan is not working"
See it here: http://www.manualslib.com/manual/839570/Panasonic-Sa-Bt100p.html?page=29
I also saw a reference to checking the cooling fan is clear and rotating freely
More at:
http://www.fixya.com/support/t21395272-panasonic_error_f61
http://www.ehow.com/how_8752100_fix-panasonic-home-theater-system.html
You could always try this:
http://lmgtfy.com/?q=SA-BTT750+error+F61
X, February 2015
