Vintage Synth Repair

I got a Roland MKS70 of which the Power Supply unregulated voltage rail 
is too high. The schematics says there should be +7v but I read 11V 
when the DMM is set to DC and 28v when set to AC !

This fits with the fact that the display of that unit is overbright, 
showing all characters at once....

But what can cause the unregulated voltage to be incorrect ?
could this be bad regulators in the PS unit ??

I already replaced all capacitors in the PS.

Thanks all !!