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Audio amp quiscent current


Paul_J
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I replaced a STK3062 in a Marantz PM-52SE power amp with another module.
The output DC offset voltage is 0 but the quiscent current in 700mA.  :o
What should I do to reduce it to 70mA?

Here's a list with the values of the components of the replacement module:

R1______________47K  1/4W Resistor
R2_______________4K7  1/4W Resistor
R3______________22K  1/4W Resistor
R4_______________1K  1/4W Resistor
R5_____________330R  1/4W Resistors
R6_______________1K5  1/4W Resistor
R7______________15K  1/4W Resistor
R8______________33K  1/4W Resistor
R9_____________150K  1/4W Resistor
R11_____________39R  1/4W Resistor

C1_____________470nF  63V Polyester Capacitor
C2_____________470pF  63V Polystyrene or ceramic Capacitor
C3______________100uF  63V Electrolytic Capacitor
C4_____________100nF  63V Polyester Capacitors
C5______________10pF  63V Polystyrene or ceramic Capacitor

Q1,Q2,Q3,Q4,Q5_____MPSA42  300V 500mA NPN Transistors
Q6___________MJE340  200V 500mA NPN Transistor
Q7___________MJE350  200V 500mA PNP Transistor

post-23437-14279143176934_thumb.gif

STK_3042-3062-3082-3102-3122-3152_III_-_Sanyo.pdf

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If your amplifier circuit has a trimpot to adjust the amount of idle current then it will connect to a transistor or couple of series diodes connected to the outer of the 3 pins of your new module. Probably the new module passes a different amount of current through the adjustment part so it causes a higher idle current.

Attach a schematic of the output circuit to see the adjustment trimpot and what can be changed to get a better current adjustment range.

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Because it's a rare amp I don't have a schematic. It's hard to guess it by looking at the PCB tracks because there's also a circuit that detects if there's DC at the output.

I think the value of the trimpot is too large. The trimpot connects to a transistor.
If this doesn't work I'll use a couple diodes.

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I think the value of the trimpot is too large. The trimpot connects to a transistor.

Maybe Marantz copied Sanyo's circuit. Increasing the value of the pot turns on the transistor, then the idle current is reduced. A resistor is on the other side of the transistor to turn it on, reduce its value to reduce the idle current.
It would be difficult to find a trimpot the same physically but with a higher resistance.
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