V1- 12AX7, Rhythm channel
V2- 12AX7, Lead Channel
V3- 12AX7, Reverb Driver
V4- 12AX7, Reverb/effects
V5- 12AX7. Phase Inverter
V6,V7- 6L6GC, Output
V8, V9- 6L6GC, Output (100 Watt)
or
- 12AR4, 50 Watt Dual Tube Rect
LINE CORD- For your safety, connect to grounded A/C receptacle only.
Each fine production tube is tested and matched to our exacting specifications. External bias adjustment and
test points are located on the chassis near the output tube sockets. A digital voltmeter and small screwdriver are
required for bias adjustment.
BIAS ADJUSTMENTS:
Power up unit and connect proper speaker load.
Set master volumes and effects return controls to zero.
DO NOT
apply any signal to the input during the biasing procedure!
Take unit off standby and allow a few seconds for the circuit to stabilize.
Set voltmeter to Millivolt scale (or lowest volt scale 60 millivolts=.060 volts.)
With meter grounded to chassis and + probe at test point, measure voltage.
A reading of 0.055 to 0.060 volts is normal for 50 Watt amplifiers with (2) 6L6’s. A reading of 0.115 to 0.120
volts is normal for 100 Watt amplifiers with (4) 6L6’s. If not in this range, adjust by turning bias screw SLOW
-
LY a small amount.
Do not set above .070!
For other tube types (5881, 6550, EL34) check with the manufacturer or contact us for recommendations.
Settings higher than .065 with 6L6 tubes may cause premature tube wear and possibly damage the amplifier.
Keep in mind that tubes vary in quality, and some tubes can handle upwards of 40 ma each (a reading at the test
point of .080!) However, to be on the safe side, use the above as a guide.
NOTE:
Some amps are equipped with 2 bias pots, one for low power, the other for high power. Adjust bias in
both hi and low power settings!
NOTE:
Some amps are Class A/AB. In LOW POWER MODE(CLASS A)
, you will not get a proper reading-
adjust bias in high power mode only.
WARNING!
No user serviceable parts inside! Refer to qualified service person only.
