Tube Tech PA6 - Manual (Page 2)

LYDKRAFT ApS
Ved Damhussøen 38,DK 2720 Vanløse
Denmark
2
ADJUSTMENT PROCEDURE:
INITIAL ADJUSTMENT:
POWER SUPPLY:
The power supply PCB is located on the rear panel.
1. Adjust the voltage for the output stage to 155V with P1.
AMPLIFIER OUTPUT STAGE:
IMPORTANT:
After replacement of output tubes, it is important that the "initial bias adjustment"
is carried out.
If this step is neglected, the output tubes may be permanently damaged, due
to the possibility of high cathode current.
INITIAL BIAS ADJUSTMENT:
1. Turn off Volume.
2. Place a voltmeter between TP3 for the left channel (TP6 for the right
channel) and 0V.
3. Turn on power.
4. Observe that the voltage does not exceed 10 V after a few minutes,
otherwise adjust with the multiturn trimpot marked "BIAS".
BIAS AND BALANCE ADJUSTMENT:
1. 10-15 minutes after power turn on, the current in the output tubes has
stabilized and the bias and balance can be adjusted with a voltmeter.
2. Place the voltmeter between TP1 and TP3 and adjust the voltage to
50mV (< +/-2mV) with the multiturn trimpot marked BIAS.
3. Place the voltmeter between TP1 and TP2 and adjust the voltage to
0V (< +/-1mV) with the multiturn trimpot marked BALANCE.
4. Repeat step 2-4 until correct.
cont.