Roland A-90 EX seems to have a power supply problem

Hello word!
my Roland A-90 EX seems to have a power supply problem.
When it’s first on after being off for a while, it’s play fine for about 10 mins,
then the display dims and it’s as if the power was interrupted briefly.
The unit goes through it’s normal power-up sequence and is
playable again for a little while, then the cycle repeats again.
What’s wrong with it?

Thank for your idea!
and have a nice day…

Finally, i find the solution !
after several booting, when I had to give a little hit on the keyboard on the power side,
to see lcd light on,
I decide to disasembling the power board, and after good examine,
i see one of the three transistor wich was nearly desoldered.
So i resolded it and the the two other so.
i profite the intervention to ad four littlle feutre silent block, as the transformer unit was very noisy.
It work fine.
YES!!! go for the music now…