15
Power Consumption
With no signal and no load, the power consumption from the AC mains should be:
Variac Power consumption
Up to 40vac < 3W
Up to 60vac < 8W
Up to 120vac < 40W
DC supplies
Set the Variac up to 120vac (US models)
Measure the DC supplies: (see page 204-4 for the pcb layout)
+69 to +71vdc Q5 Pin 2
–69 to –71vdc Q50 Pin 2
+59 to +61vdc Q10 Pin 2
–59 to –61vdc Q47 Pin 2
+14 to +15.5vdc U1 Pin 3
–14 to –15.5vdc U2 Pin 3
+4.75 to +5.25vdc Across U5 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 the two pins of J7
Adjust R2 for 19 to 21mvdc,
Seal the pot with a drop of nail paint
Channel 2
Measure the DC voltage between the two pins of J6
Adjust R1 for 19 to 21mvdc
Seal the pot with a drop of nail paint
Power Tests
Continuous Sine Wave Average Output Power, both channels driven (rated power):
180 watts per channel into 4Ω from 40Hz to 20kHz, with no more than 0.15% THD
110 watts per channel into 8Ω from 40Hz to 20kHz, with no more than 0.10% THD
Check for symmetrical clipping.
Amplifier tests for the 406M/408M/408S
Q1
Q2
Q3
Ch.2 Bias
Pot R1
Q7
Q8
+15VDC
Regulators
+ 5VDC
regulator
-15VDC
U1 U2
Q9
Channel 1 NPN
Channel 1 PNP
Channel 2 NPN
Channel 2 PNP
60 Volt Rect.
Q10
Q4
Q5
Q6
Q44
Q49
Q48
Q45
U5 TH1
D66
J10
J1
Q46 Q47
ecbecbecbecb
bcebcebcebce
Q50
Q51
Ch.2
Bias test points
J6
Ch.1
Bias test points
J7
Ch.1 Bias
Pot R2
This is the 204 amplifier circuit board, see chapter 204 for more details
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