Mackie 406M Service Manual page 15
Ppm series
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Also See for 406M:
- Specifications (6 pages) ,
- Hook-up manual (7 pages) ,
- Owner's manual (36 pages)
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Amplifier tests for the 406M/408M/408S
Power Consumption
With no signal and no load, the power consumption from the AC mains should be:
Variac
Up to 40vac
Up to 60vac
Up to 120vac
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
–69 to –71vdc
+59 to +61vdc
–59 to –61vdc
+14 to +15.5vdc
–14 to –15.5vdc
+4.75 to +5.25vdc
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.
Channel 2 NPN
Ch.2 Bias
Pot R1
Q7
Q2
b c e
Q1
Q3
e c b
Q48
Q49
Q44
Channel 2 PNP
This is the 204 amplifier circuit board, see chapter 204 for more details
Power consumption
< 3W
< 8W
< 40W
Q5 Pin 2
Q50 Pin 2
Q10 Pin 2
Q47 Pin 2
U1 Pin 3
U2 Pin 3
Across U5 Pins 2 & 3
Regulators
+15VDC
-15VDC
Ch.2
Q8
Bias test points
J6
U1
U2
b c e
J10
e c b
U5
TH1
Q45
+ 5VDC
regulator
60 Volt Rect.
Channel 1 NPN
Ch.1
Q9
Bias test points
J7
b c e
e c b
Q46
D66
Channel 1 PNP
Ch.1 Bias
Pot R2
Q10
Q5
b c e
Q6
Q4
J1
e c b
Q51
Q50
Q47
15
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