RedPlate Black-n-Blues Operations Guide
9
7. Use a small flat blade screwdriver to adjust the bias pot for a reading of 50MV ± 5 MV (FYI
- the plate voltage is 380 volts). 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.
BIAS PROCEDURE - 45 Watt Model w/ 2 6L6 tubes
1. The 45 watt model can also be configured for use with two 6L6 GC output tubes. No
biasing needed for 6L6 tubes installed as the outside pair (V6 & V9) because they will be
running in cathode bias mode.
2. CAUTION - REMOVE ALL FOUR 6V6 TUBES BEFORE INSTALLING TWO 6L6 GC
TUBES, NEVER MIX 6L6 AND 6V6 TUBES AND 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 read lead is the DC voltage terminal of the
meter.
4. Install the 6L6 GC tubes into the inner pair sockets (V7 & V8)
5. Place the Amplifier in operate mode with the Master Volume set to zero.
6. Set the 45 WATT/ 18 WATT switch to the 45 WATT position.
7. 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.
8. Use a small flat blade screwdriver to adjust the bias pot for a reading of 80MV ± 5 MV (FYI
- the plate voltage is 380 volts). The reading is the sum of the idle current for both tubes.
9. Recheck the reading after 10 minutes of operation, and again after a week or two of
operation.
BIAS PROCEDURE 100 Watt Model
1. When new 6L6 GC 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 read lead is the DC voltage terminal of the
meter.
4. Place the Amplifier in operate mode with the Master Volume control set to zero.
5. Set the 100 WATT/ 50 WATT switch to the 100 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 a reading of 144MV ± 5 MV (FYI
- the plate voltage is 440 volts). The reading is the sum of the idle current for all 4 tubes.
8. Recheck the reading after 10 minutes of operation, and again after a week or two of
operation.
