E20 or E21 error on Mr850 is more than just a fuse problem.
There is a +/- 11.3V regulator circuit components that ususally fails.
If you look at one of the capacitors 47uF/50V, is a bit discolored compared to the one beside it. Those 2 capacitors are the filters for the rectified voltage input to the regulator circuit (series pass transistor regulator configuration). What
fails is the SM transistor and zener diode.
I hope this might help you in the future
