Not often I throw my hands up,but this is an odd one.Switch on green light flashes settles to stable green,you get sound but no display at all not even a flash.The screen buzzes,output signal to a set via scart you get sound & picture changes channels o.k.voltages from psu sit at 195 & 100volts theres vd rail at 65volts which I think feeds the bottom buffers,5volt supplies,15volt supplies all appears to be good.Ive got a green led on both the ysus & z sus which are on.Any ideas,What have I missed.I have disconnected the buffers & shorted sc50 on y sus,screen still buzzes.HELP!