diff --git a/src/mame/drivers/rainbow.cpp b/src/mame/drivers/rainbow.cpp
index 2ee85a262c3..c3920826af3 100644
--- a/src/mame/drivers/rainbow.cpp
+++ b/src/mame/drivers/rainbow.cpp
@@ -3203,7 +3203,7 @@ MCFG_SCREEN_UPDATE_DRIVER(rainbow_state, screen_update_rainbow)
 MCFG_SCREEN_PALETTE("vt100_video:palette")
 MCFG_GFXDECODE_ADD("gfxdecode", "vt100_video:palette", rainbow)
 
-MCFG_DEVICE_ADD("vt100_video", RAINBOW_VIDEO, 0)
+MCFG_DEVICE_ADD("vt100_video", RAINBOW_VIDEO, XTAL_24_0734MHz)
 
 MCFG_VT_SET_SCREEN("screen")
 MCFG_VT_CHARGEN("chargen")
diff --git a/src/mame/drivers/vt100.cpp b/src/mame/drivers/vt100.cpp
index 4159561cb46..447e4b065e3 100644
--- a/src/mame/drivers/vt100.cpp
+++ b/src/mame/drivers/vt100.cpp
@@ -425,7 +425,7 @@ static MACHINE_CONFIG_START( vt100 )
 
 	MCFG_DEFAULT_LAYOUT( layout_vt100 )
 
-	MCFG_DEVICE_ADD("vt100_video", VT100_VIDEO, 0)
+	MCFG_DEVICE_ADD("vt100_video", VT100_VIDEO, XTAL_24_0734MHz)
 	MCFG_VT_SET_SCREEN("screen")
 	MCFG_VT_CHARGEN("chargen")
 	MCFG_VT_VIDEO_RAM_CALLBACK(READ8(vt100_state, vt100_read_video_ram_r))
@@ -440,7 +440,7 @@ static MACHINE_CONFIG_START( vt100 )
 	MCFG_RS232_RXD_HANDLER(DEVWRITELINE("i8251", i8251_device, write_rxd))
 	MCFG_RS232_DSR_HANDLER(DEVWRITELINE("i8251", i8251_device, write_dsr))
 
-	MCFG_DEVICE_ADD(COM5016T_TAG, COM8116, XTAL_5_0688MHz/*XTAL_24_8832MHz / 9*/) // COM5016T-013, 2.7648Mhz Clock, currently hacked wrongly
+	MCFG_DEVICE_ADD(COM5016T_TAG, COM8116, 5068800/*XTAL_24_8832MHz / 9*/) // COM5016T-013, 2.7648Mhz Clock, currently hacked wrongly
 	MCFG_COM8116_FR_HANDLER(DEVWRITELINE("i8251", i8251_device, write_rxc))
 	MCFG_COM8116_FT_HANDLER(DEVWRITELINE("i8251", i8251_device, write_txc))
 
diff --git a/src/mame/video/vtvideo.cpp b/src/mame/video/vtvideo.cpp
index a51fdd3bf64..43db3a386f7 100644
--- a/src/mame/video/vtvideo.cpp
+++ b/src/mame/video/vtvideo.cpp
@@ -209,7 +209,7 @@ void vt100_video_device::recompute_parameters()
 		horiz_pix_total = m_columns * 10; // normal 80 character mode.
 
 	visarea.set(0, horiz_pix_total - 1, 0, vert_pix_total - 1);
-	machine().first_screen()->configure(horiz_pix_total, vert_pix_total, visarea, HZ_TO_ATTOSECONDS((m_interlaced == 0) ? m_frequency : (m_frequency/2) ));
+	screen().configure(horiz_pix_total, vert_pix_total, visarea, HZ_TO_ATTOSECONDS((m_interlaced == 0) ? m_frequency : (m_frequency/2) ));
 
 	if (VERBOSE)
 	{