14
Power Consumption
With no signal and no load, the power consumption from the AC mains should be:
Variac Power consumption
Up to 40vac < 5W
Up to 60vac < 20W
Up to 120vac < 50W
DC supplies
Set the Variac up to 120vac (US models)
Measure the DC supplies: (see page 193-5 for the pcb layout)
+96 to +98vdc @pcb test point +100v
–96 to –98vdc @pcb test point -100v
+86 to +89vdc @pcb test point +90v
–86 to –89vdc @pcb test point -90v
+42 to +44vdc @pcb test point +45v
–42 to –44vdc @pcb test point -45v
+14.5 to +16.5vdc U1 Pin 3
–14.5 to –16.5vdc U2 Pin 3
+4.75 to +5.25vdc U7 Pins 2 & 3
Bias Adjustment
The bias adjustment is best done when the amplifier has been warmed up. Run it with a music
program into a dummy load until the heatsink is warm to the touch.
The actual adjustment is done with no signal and no load:
Channel 1
Measure the DC voltage between J23 & J24
Adjust R7 for 18 to 20mvdc,
Seal the pot with a drop of nail paint
Channel 2
Measure the DC voltage between J21 & J22
Adjust R6 for 18 to 20mvdc
Seal the pot with a drop of nail paint
Power Tests
Continuous Sine Wave Average Output Power, both channels driven (rated power):
340 watts per channel into 4
Ω
from 40Hz to 20kHz, with no more than 0.15% THD
240 watts per channel into 8
Ω
from 40Hz to 20kHz, with no more than 0.10% THD
Check for symmetrical clipping and correct operation of the DC rail switching.
Amplifier tests for the 808M and 808S
Q1
Q2
Q3
Q9 Q10 Q11
Q7
FET FET
FET FET
D1 U1 U2
D4
D2
Q8
Q12 Q13 Q14
Q4
Q5
Q6
Q68
Q74
Q78
Measure
Bias Ch. 2
DC Rail
test points
Test
points
Q69 Q70
Q75 D100 U7 TH1
D99
D101
Q76
Q71
b c e b c e b c e
e c b e c b e c b
e c b e c b e c b
b c e b c e b c e
Q72 Q73
Q77
Q79
Ch.1 Bias pot R7
Ch.1 NPN
90 Volt rect.
+15V
Reg
-15V
Reg
+5V
Reg 45 Volt rect.
Ch.1 PNP
Ch.2 NPN
Ch.2 PNP
Ch.2 Bias pot R6
Test
points
Measure
Bias Ch. 1
This is the 193 amplifier circuit board, see chapter 193 for more details
