Bias Procedure - RedPlate MagicDust Operation Manual

RedPlate MagicDust Operations Guide
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.
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 and Reverb controls set to
zero.
5. Set the 100 WATT/ 17 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 four tubes.
8. Recheck the reading after 10 minutes of operation, and again after a week or two of
operation.

BIAS PROCEDURE

INTERNAL TRIM POT(S)
7