RedPlate BlackLine/BluesLine Operations Guide
6
TUBE CHART
All tube brands are acceptable, a long plate is preferred in the V5 (Phase Inverter) position.
Warning
– No user serviceable parts inside so unless you know what you’re
doing please refer to a qualified service person only.
BIAS PROCEDURE
1. When new EL-34 output tubes are installed it is important to re-bias the amp for optimal
performance.
2. ALWAYS HAVE A SPEAKER CONNECTED.
3. Use a digital volt meter set to DC volts at lowest scale (MV). Makes sure the black lead is
the common terminal of the meter and the red lead is the DC voltage terminal of the meter.
4. Place the Amplifier in operate mode with the Master Volume set to zero.
5. Set the 50 WATT/ 18 WATT switch to the 50 WATT position.
6. Place the red meter lead in the test point hole (red tip jack) and touch (or clip) the black
meter lead on one of the metal output tube retainer clips.
7. Use a small flat blade screwdriver to adjust the bias pot for the bias number as stated on
the rear panel ( ± 5 MV). The reading is the sum of the idle current for both tubes.
8. Recheck the reading after 10 minutes of operation, and again after a week or two of
operation.