Friday, February 22, 2019

S.Kinder's Yamaha CA-610 MKII Integrated Amplifier Restoration

Yamaha CA-610 MKII Integrated Amplifier



Produced in the late 70’s after 77” the Mark II variant featured a 50 Watt output at .05%THDN. The CA-610MKII utilizes a cost-effective single main PCB design for most of the PS and AF front end stages with calibrated meter output.


Regulated Power Supply & Protection
The regulated power supply is contain on the single main large PCB of the unit. A full-wave rectifier bridge is employed for the -/+B source and a simplified full-wave for the AF/RIAA front end supply. The protection stage is also contained therein which monitors thermal run-off and DC deviation of the output stage.

The simplified rectifier array was replaced with ultra-fast, soft recovery dial Vishay diodes. The TO-220 regulator was replaced with a modern, robust TIP device thermally coupled with synthetic thermal compound, remaining small signal devices were replaced with modern, TO92/(L) type Fairchild devices. 


Bypass capacitors were replaced with Nichicon polypropylene film capacitors. Remaining electrolytic were replaced with low impedance, high temp (105C) Nichicon PW type with an increase in decoupling stage and operating voltages.  New 10,000MFD computer grade capacitors installed for the -/+B supply.


AFTER



-/+BVdc Confirmation

Main PCB Driver Section
Like the regulated supply the driver stage is housed on the main PCB with symmetric drivers and  complimentary output stage and differential input. 

The common emitter PNP devices were replaced with single discrete matched, low noise TO92 Fairchild devices. All of the small devices were replaced with modern TO-126, TO92L Fairchild devices with better dissipation. TO3 output devices were replaced in complimentary pairs with modern, On-Semi type with new thermal compound applied. New general axial 4148 diodes installed and precision bias potentiometers installed.




Differential Mapping

Electrolytic capacitors were replaced with audio grade KT/KA and low impedance Nichicon PW type with an increase in operating voltages. Ceramic and small value capacitors were replaced with high grade WIMA polypropylene film capacitors.


BEFORE


AFTER



Bias Confirmation

Tone Amp & Controll
The pre-amp, housed also on the main PCB area. Consisting of a simple single-end front end and output stage. The control PCB for tone attenuation is located on a separate PCB perpendicular to the chassis mount. Control hardware including the multi-gang volume/balance potentiometer were removed and properly treated.


The small signal devices were replaced with modern, low noise Fairchild devices. Small value and ceramic capacitors were replaced with high grade WIMA polypropylene film capacitors. Capacitors were replaced with audio grade KT/KA and low impedance Nichicon PW type with an increase in operating voltages. 



BEFORE



AFTER




RIAA EQ (PHONO)
The phono stage is located on a separate plane PCB with the input and selector points onboard.

All of the small signal devices were replaced with modern, low noise TO-126 and TO-92 Fairchild devices. Small value and ceramic capacitors were replaced with high grade WIMA polypropylene film capacitors. Capacitors were replaced with audio grade KT/KA and low impedance Nichicon PW type with an increase in operating voltages. 


BEFORE


AFTER



RIAA Curve Response

Meter Assembly
The calibration point had the original adjustment hardware replaced with precision, sealed Bourns potentiometers. Axial diodes were replaced with general axial 4148 type axial diodes. The original incandscenet lamps were also replaced with cool white LED’s with current drop modifications.


BEFORE


AFTER

AUDIO NOTIZEN



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