diff --git a/include/userio.h b/include/userio.h
index 2f64924..65b79cf 100644
--- a/include/userio.h
+++ b/include/userio.h
@@ -32,6 +32,8 @@ void userio_parse();
 uint8_t userio_get_mode();
 int16_t userio_get_btn();
 
+uint8_t userio_get_set1_limit();
+
 
 
 #endif /* _INC_USERIO_H */
\ No newline at end of file
diff --git a/src/rgbprog.c b/src/rgbprog.c
index fa6e0cd..a585675 100644
--- a/src/rgbprog.c
+++ b/src/rgbprog.c
@@ -43,6 +43,8 @@ void rgbprog_randcolor(uint8_t k0);
 void rgbprog_randcolorfadeinout(uint8_t k0);
 void rgbprog_prog7(uint8_t k0);
 
+void rgbprog_set1_error();
+
 static void (*proglist[8])(uint8_t) = {
 	rgbprog_rainbow,
 	rgbprog_rainbow_offset,
@@ -111,6 +113,13 @@ void rgbprog_run()
 		brite++;
 		brite &= 0x3;
 	}
+
+	// if SET1 is out of range, indicate that instead of
+	// running the normal program
+	if (userio_get_set1_limit()) {
+		rgbprog_set1_error();
+		return;
+	}
 	
 	// which program to run?
 	j = 0;
@@ -389,4 +398,27 @@ void rgbprog_prog7(uint8_t k0)
 	rgb[0].r = rgb[0].g = rgb[0].b = 0;
 	rgb_setled(0, &rgb[0]);
 	rgb_setled(1, &rgb[0]);
+}
+
+/*
+ * internal program:
+ *
+ * flashes LEDs, indicating a SET1 knob error.
+ */
+void rgbprog_set1_error()
+{
+	hsv[1].s++;
+	if (!hsv[1].s) {
+		hsv[1].v++;
+		hsv[1].v &= 1;
+		hsv[0].v = hsv[1].v ^ 1;
+
+		rgb[0].r = 255;
+		rgb[0].g = 0;
+		rgb[0].b = 0;
+		rgb_setled(hsv[1].v, &rgb[0]);
+
+		rgb[0].r = 0;
+		rgb_setled(hsv[0].v, &rgb[0]);
+	}
 }
\ No newline at end of file
diff --git a/src/userio.c b/src/userio.c
index d7a5e4a..d2a020f 100644
--- a/src/userio.c
+++ b/src/userio.c
@@ -42,7 +42,7 @@
 
 
 #ifdef TESTO_REV1
-#define SET1_MAX			2047	// 3V net feeding into 1V24 via body diode above this
+#define SET1_MAX			2199	// 3V net feeding into 1V24 via body diode above this
 #else
 #define SET1_MAX			1539	// 1.24Vref
 #endif
@@ -174,5 +174,18 @@ int16_t userio_get_btn()
 		}
 	}
 
+	return 0;
+}
+
+/*
+ * returns true if the right knob is beyond maximum range.
+ * always returns false on REV2 or later boards.
+ */
+uint8_t userio_get_set1_limit()
+{
+#ifdef TESTO_REV1
+	if (adc_avg[ADC_SET1] > SET1_MAX) return 1;
+#endif
+
 	return 0;
 }
\ No newline at end of file