diff --git a/src/mame/drivers/lockon.cpp b/src/mame/drivers/lockon.cpp
index d145b358c58..d9474d316a1 100644
--- a/src/mame/drivers/lockon.cpp
+++ b/src/mame/drivers/lockon.cpp
@@ -414,20 +414,12 @@ WRITE_LINE_MEMBER(lockon_state::ym2203_irq)
 
 WRITE8_MEMBER(lockon_state::ym2203_out_b)
 {
-	// we require that the value keeps stable for at least two writes
-	if (BIT(data, 7) == BIT(m_ym2203_port_b, 7))
-		machine().bookkeeping().coin_counter_w(0, BIT(~data, 7));
-
-	if (BIT(data, 6) == BIT(m_ym2203_port_b, 6))
-		machine().bookkeeping().coin_counter_w(1, BIT(~data, 6));
-
-	if (BIT(data, 5) == BIT(m_ym2203_port_b, 5))
-		machine().bookkeeping().coin_counter_w(2, BIT(~data, 5));
+	machine().bookkeeping().coin_counter_w(0, data & 0x80);
+	machine().bookkeeping().coin_counter_w(1, data & 0x40);
+	machine().bookkeeping().coin_counter_w(2, data & 0x20);
 
 	/* 'Lock-On' lamp */
 	m_lamp = BIT(~data, 4);
-
-	m_ym2203_port_b = data;
 }
 
 /*************************************
diff --git a/src/mame/includes/lockon.h b/src/mame/includes/lockon.h
index d21db6256d6..abdbbe9219c 100644
--- a/src/mame/includes/lockon.h
+++ b/src/mame/includes/lockon.h
@@ -36,7 +36,6 @@ public:
 		, m_scene_ram(*this, "scene_ram")
 		, m_ground_ram(*this, "ground_ram")
 		, m_object_ram(*this, "object_ram")
-		, m_ym2203_port_b(0xff)
 		, m_maincpu(*this, "maincpu")
 		, m_audiocpu(*this, "audiocpu")
 		, m_ground(*this, "ground")
@@ -98,7 +97,6 @@ private:
 	/* misc */
 	uint8_t       m_ctrl_reg;
 	uint32_t      m_main_inten;
-	uint8_t       m_ym2203_port_b;
 
 	/* devices */
 	required_device<cpu_device> m_maincpu;