Top Panel
9
1.Be careful of the high temperature of the tubes during operation.
2.Replace the tubes carefully and correctly.
3.Power tubes must be matched for well function.
NOTE:
1 2 3 1
2
3
4 4765 5 8
.
2.
3.A1、A2、A3、A4:300B Tube
4.V2、V3、V5、V6:12AU7 Tube
5.V1、V4:12AX7 Tube
6.V7:6SN7 Tube
7.
8.HUM BALANCE
1Bias Selector Switch(A1、A2、A3、A4)
Used to select corresponding tube for bias
adjustment.
Bias Adjustment Switch(A1、A2、A3、A4)
Used to adjust bias of corresponding power
tube(A1、A2、A3、A4)
Bias Meter
Used to monitor the working current of the
power tube.
Adjustment Swith
How to adjust the 300B HUM:
Turn the volume knob to the minimum or mute
and adjust the HUM BALANCE with the flat
screwdriver until you heard the smallest HUM.
Do the same for adjusting the other channel.
Bias adjustment for the power tube:
Turn the Bias Selector Switch to its opposite
direction without releasing it, adjust the
corresponding Bias Adjustment Switch with flat
screwdriver, and inspect the Bias Meter on the
top panel to make sure the pointer keeps in the
center. Bias adjustment for A1 A2 A3 A4 are the
same. After all have been djusted, do it one more
time to make sure all the bias levels of A1,A2, A3,
A4 are the same.
Sample of bias adjustment for power tube A1:
1. Turn the Bias Selector Switch A1 to its opposite
direction without releasing it.
2. Adjust the corresponding Bias Adjustment Switch
A1 with flat screwdriver until the pointer of the
bias meter keeps in the center.
3. Adjustment for A2, A3, A4 are the same.
A
Diagram 5
Bias meter during working
Note: When working normally,
the pointer should stay within
the A zone, still , it would move
for the voltage fluctuation.
Diagram 4
Bias meter when not working
