Sony TA-4650
35W Stereo Integrated Amplifier
Description
V-Fet is the acronym for the newly developed vertical type field effect power transistors used in the TA-4650 amplifier.
A V-Fet has extremely low output impedance and excellent high power capability, delivering an output current proportional to input voltages and assuring virtually distortion free amplification.
Use of the V-Fets in the power output stage results in a quality of reproduction hitherto not available to audiophiles.
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instruction/owners manual (en, de, fr)
service manual (en)
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Comments
Sony TA-4650
Submitted on December 20th, 2009 by draper333Produced from 1974 to 1978, this Service Manual is from 1975.
My example serial # 805653 has in the phono section 2SK79 low power V-Fet's. In case of an overhaul the diodes D302, D352 and the D414 should be replaced with two serial connected silicon diodes, like the 1N4148. The D302/352 are thermally connected to the transistors Q307 and Q357. There after the bias should be readjusted. The 75mV mentioned in the manual for the bias value is probably to high. It would result 2x159mA bias current and a total of 27W dissipation. Try to adjust the bias so at the heath sink temperature is ca. 25-30 celsius above the ambient temperature. The heath sink size (19x12x4.5cm) is shorter (-5cm) than the TA-5650s, but a bit taller, also the 4650 missing the chimneys over the heath sinks. The speaker connectors are the simplest but most reliable ones of the three amps ,the TA-8650 being the worst of this regard (falling a part).