Toshiba MSX (HX-10) 64K Black screen

hi guys i have here a
Toshiba MSX (HX-10) 64K

black screen i replaced the lva 510 chip even replaced the Tms9929anl chip still the same what else should i try to fix this i would at least want to get to the basic on this as it would be cool once fixed.

thanks.

Caps-Lock LED dont come on when the key is pressed
Pressing Ctrl+G outputs a beep but does not.

I was thinking CPU or transistors

 

Is there are clock signal? can you see activitty on the databus ? (try a led and resistor)
Basicly what I can think of. If your realyy suspect the cpu, try the z80 tester: http://www.z80.info/z80test0.htm