st7920 showing all pixels

Hello,
I'm trying to get a ST7920, 128 x 64 LCD to display anything at all, but all the pixels are on.

Its wired to a arduino mega2560 like this:

pin 1 to gnd
pin 2 to +5v
pin 4 to D18
pin 5 to D17
pin 6 to D16
pin 15 to gnd
pin 19 to 3.3v
pin 20 to gnd

If i try to ajust the pod in the back of the lcd, either it goes all blue or all pixels (white) are showing.
There is no R9 jumper to remove.

What am i doing wrong?

I'm using the included example Hello world, with the following code:

#include "U8glib.h"

// setup u8g object, please remove comment from one of the following constructor calls
// IMPORTANT NOTE: The following list is incomplete. The complete list of supported 
// devices with all constructor calls is here: http://code.google.com/p/u8glib/wiki/device

U8GLIB_ST7920_128X64_1X u8g(18, 16, 17);	// SPI Com: SCK = en = 18, MOSI = rw = 16, CS = di = 17


void draw(void) {
  // graphic commands to redraw the complete screen should be placed here  
  u8g.setFont(u8g_font_unifont);
  //u8g.setFont(u8g_font_osb21);
  u8g.drawStr( 0, 22, "Hello World!");
}

void setup(void) {
  // flip screen, if required
  // u8g.setRot180();
  
  // set SPI backup if required
  //u8g.setHardwareBackup(u8g_backup_avr_spi);

  // assign default color value
  if ( u8g.getMode() == U8G_MODE_R3G3B2 ) {
    u8g.setColorIndex(255);     // white
  }
  else if ( u8g.getMode() == U8G_MODE_GRAY2BIT ) {
    u8g.setColorIndex(3);         // max intensity
  }
  else if ( u8g.getMode() == U8G_MODE_BW ) {
    u8g.setColorIndex(1);         // pixel on
  }
  else if ( u8g.getMode() == U8G_MODE_HICOLOR ) {
    u8g.setHiColorByRGB(255,255,255);
  }
}

void loop(void) {
  // picture loop
  u8g.firstPage();  
  do {
    draw();
  } while( u8g.nextPage() );
  
  // rebuild the picture after some delay
  delay(50);
}