ACCUPHASE E202 POWER SECTION

ACCUPHASE E202 is an Integrated Amplifier made by ACCUPHASE made in the 70s.

The power amplifier uses 2 pairs of power transistors that require a symmetrical supply of 55VDC.

AMPLIFIER DATASHEETS HERE.

SCHEMATIC DIAGRAM

Result of cropping schematic from original one are shown below:

Firstly preamp uses 2SA620 transistors. Voltage Amplifier Stages use transistor 2SC1451 (Q3) and amplified again by 2SC515A (Q4).

The + supply comes from the voltage are maintained by the 6.2 VDC Zener diode.

To make a zero volt output or DC0, this circuit uses a 4K7 VR2 trimpot which is the point of taking the bias voltage between -0.6VDC to +0.6VDC.

There are no transistor that acts as a servo driver.

Its only uses a passive diode STV-4H and is connected in series with a 100 Ohm trimpot / 5TP-31L Thermistor.

There is an Over Current Protection feature by transistors Q5 and Q7 which use transistor 2SC1416 and 2SA776.

The driver transistors are using the 2SC1431/2SA672 pair.

Lastly is the final Power Transistor using the 2SC1079 / 2SA679 pair.

NOTE

Power supply for this amplifier circuit includes +16,2VDC and -59VDC for the preamp circuit.

+79 VDC is to biasing the driver transistor.

Also +55VDC and -55VDC to supplying the Final Power Amplifier transistor.

Gain factor of this amplifier is determined by the resistor R9/R8.

2SC1079 and 2SA679 final power transistors have a dissipation ability of up to 100 W ( DATASHEETS ).