F. Church Yamaha CA-1010 Integrated Amp Restoration

Yamaha CA-1010 Integrated Amplifier

The Yamaha CA-1010 (CA-1000III Japanese Markets) was produced from 1977 to 1978 proceeding the large 2010 variant.  Unique in its Class A/AB switch mode this CA series remains one of the most popular vintage integrated amplifiers today, many of the features and build qualities used was later fashioned into high end Yamaha amplifiers.

Power Supply / Protection

The Yamaha CA-1010 features a very robust power supply circuit, with a variable output depending on Class A or A/B operation. The primary driver supply consists of two 18,000MFD filter capacitors off a bridge rectifier array (also housing the Soft Start relay action).  The regulated stage consists of two 1A bridge rectifiers delivering the 30/62 -/+V dual supplies. The Protection circuit is also house on this assembly. Featuring multiple lines of protection such as excessive current consumption and output shorting including the Area of Safe Operation (ASO) thermal protection circuit. 

All of the electrolytic capacitors were replaced with Bipolar and  low impedance, high temp (105C) Nichicon PW with an increase in operating voltages. The initial DC filtering capacitors were increased to 330MFD, DC output filtering to 220MFD and protection AC/DC filtering to 100 and 220MFD capacitances for significantly better filtering and noise reduction of the power supply. 

All of the bridge arrays were replaced with Ultra-Fast, Soft Recovery Fairchild axial diodes. Small signal devices were replaced with a low noise TO-92L/92 type Fairchild with better dissipation. Large TO-220 regulators were all replaced with OnSemi and TIP modern, robust TO-220 devices, coupled with synthetic Wakefield thermal compound. 

BEFORE

AFTER 

Filter Capacitors + Hardware

The original 18,000MFD capacitors were replaced with new Computer-Grade Nippon Chem-Con 18KMFD capacitors. The original AC 12V array was modified to a rectified DC 8V SE source for custom multi SMD LED festoons. 

-/+ DUAL SUPPLY CONFIRMATION

AF Stage (Pre-Amplifier)

The pre-amp or line-level stage features a duel JFET and differential gain stages. The stage features stepped dual tone attenuators with a defeat option. Filters include a 10K and 15z with a 12dB cutoff. A quality 4-gang volume attenuator first used in the C-1 and C-2 high-end Yamaha pre-amplifiers. 

During the rebuild of this stage its important to remove the potentiometers from the PCB for proper cleaning as shown below. I also like to replace the hard-wired Volume PCB connectors to a stranded wired connection to avoid future solder connection issues. 

All of the electrolytic capacitors here were replaced with a audio grade Nichicon KT/KA with an increase in operating voltages. The VD type diodes were replaced with modern axial 4148 type. All the small signal devices were replaced with TO-92/TO-92L  type low noise modern Fairchild devices. Films where applicable were replaced with a high grade WIMA polypropylene film type. 

BEFORE 

AFTER

MM/MC RIAA EQ

Similar in design to the bigger 2010 model, the 1010 EQ stages feature both a MC and MM type gain stage around super-low noise FET integrated circuits in a cascade bootstrap CM design such as with the C-2 pre-amplifier stages. A impedance matching selector function is also available.

In the MC stage the electrolytic were replaced with bi-polar and low impedance PW and audio grade KT/KA Nichicons with an increase in operating voltages. New precision Bourns potentiometers also installed.

BEFORE 

AFTER

The MM stage electrolytic were replaced with a low impedance PW and audio grade KT/KA Nichicons with an increase in operating voltages. New high-grade WIMA polypropylene films installed where applicable and VD type diodes replaced with modern 4148 axial type. All small signal devices were replaced with a modern, low noise TO-92/TO-92L type Fairchild devices. 

BEFORE 

AFTER

Drivers

The CA-1010 drivers are built around a switchable Class A and AB operation which means no transient switching between traditional push pull npn/pnp output designs but at a costs of efficiency and significant heat generation even at idle. Dual differentials develop the initial gain stage as well. Dual output arrays are thermally coupled to unique dissipating star-shaped heatsinks.

The differential pairs here were matched and unlike the factory, thermally coupled together for better tracking. New pre-drivers and drivers were also installed with new OnSemi devices, coupled with synthetic Wakefield thermal compound. New A/AB adjustment potentiometers replaced with precision hardware. 

Differential Mapping

New low impedance low impedance, high temp (105C) and audio grade KT/KA Nichicon capacitors with an increase in operating voltages installed. New high grade WIMA polypropylene film capacitors installed. Vd diodes were replaced with modern axial 4148 type. 

BEFORE

AFTER

Bias Confirmation

Class A

Class A/B

Meter Assembly

The meter calibration operates the precision output meters calibrated both dB and Watts, with a 100us rise-time the display accurately transient signal and wide dynamics without peaking.  One of the issues I don’t like is the calibration positions, new pots were added to the foil side of the PCB for better future access.

Electrolytic capacitors were replaced with Bipolar and low impedance high temp (105C) Nichicon PW capacitors with an increase in operating voltages. New precision Bourns potentiometers were installed for calibration and the shield re-attached to the component side of the assembly. 

BEFORE 

AFTER

AUDIO NOTIZEN

R.Tyner Harman Kardon 930 Restoration

Harman Kardon 930 Receiver

Today were showcasing a Harman Kardon 930 Receiver, which in 1972 was one of H&K’s premier receiver line ups. Like many other H&K these utilizing a dual power supply/transformer array for superior PS designs and simplified NPN gain stages through the Af network. The 930 has a classic warmth one associates with the 70’s era hi-fi and extremely pleasing with our film and low noise compliments. 

Dual Power Supply Source

The HK 930 uses a unique dual power supply, with two separate transformers and regulator circuits per channel. The PS consists initially of two separate bridge rectifiers and a 6.3V lamp tap. Each AC/DC bridge is filtered by two 6800MFD capacitors establishing the 39V rails, one of the primary  B+ rails is then regulated for a 18Vdc AF/RF stage SE supply.

Both bridge rectifiers are comprised of two common cathode/anode devices which were replaced with Ultra-Fast, Soft Recovery On-Semi MUR type TO-220 rectification devices for cleaner DC output and less transient noise. The .1MFD bypass were replaced with high grade MKP polypropylene film capacitors. 

For the regulated PCB, the regulator device was replaced with a new On-Semi TO-220 heavy duty regulator and Wakefield synthetic compound coupled, remaining small signal device was replaced with a TO-92L Fairchild type for better dissipation. New axial viceroy 21V Zener diode was installed. The off-PCB 1000MFD and 12V 470/100MFD capacitors were all replaced with a low impedance, high temp (105C) Nichicon PW with an increase in operating voltages. A new bypass MKP polypropylene film capacitor also installed.

BEFORE 

AFTER

SE 18Vdc Confirmation

Filter Capacitors

The four 6800MFD filter capacitors were increased and replaced with new computer-grade CDE 6800MFD capacitors with an increase in operating voltages. Each of the 5.6K resistors were replaced with 5.6K 1/2W carbon type axial Vishay.

-/+ Regulated Dual B+ Confirmation

PCB 500 PRE-AMP

The pre-amp stage uses a single-ended 18V regulated supply and an entire NPN differential gain stage and coupled output stage, it features dual concentric tone attenuators.

All of the small signal devices were replaced with low noise, modern TO-92 Fairchild devices. Electrolytic capacitors were replaced with audio grade KT/KA and low impedance PW Nichicons with an increase in operating voltages. Mylar and films were replaced extensively with high-grade WIMA polypropylene film capacitors. 

BEFORE 

AFTER

PCB400 RIAA PHONO

The MM phono stage, like the proceeding AF stages is supplied by a SE regulated 18Vdc source and uses a simplified NPN gain-equalization stage. 

All of the small signal devices were replaced with low noise, modern TO-92 Fairchild devices. Electrolytic capacitors were replaced with audio grade KT/KA and low impedance PW Nichicons with an increase in operating voltages, the DC filtering capacitor was increased to 220MFD for better filtering. Mylar and films were replaced extensively with high-grade WIMA polypropylene film capacitors. 

BEFORE 

AFTER

RIAA Curve Response

PCB 600 DRIVERS 

The single PCB driver is mounted with the heatsinks open-booked to the driver assembly with a direct-coupled, push pull gain stages.

Capacitors were all replaced with low impedance PW and KT/KA audio grade Nichicons with an increase in operating voltages. Coupling and bypass films were replaced with a high-grade WIMA polypropylene film capacitors. 

The differential pairs were matched and thermally coupled with performance synthetic wakefield compound unlike the original design. Pre-drivers and drivers were all replaced with TO-92L/TO-126 type low noise, modern Fairchild devices. Epoxy diodes for the bias servo were replaced with modern 4148 general axial Vishay diodes. Both bias adjustments were were replaced with precision Bourns potentiometers.

Differential Boding Confirmation

BEFORE

 AFTER

Driver Bias Confirmation

 

PCB 300/200/100 (FM+RF)

The 930 features a very good, but problematic IC related RF tuner front end. Composed of a single IC front end ceramic filters with a four-gang tuner and FET amplifier differentials. 

All the electrolytic int these stages were replaced with low impedance Nichicon PW capacitors with an increase in operating voltages.

Muting PCB

New low impedance Nichicon PW capacitors installed with an increase in operating voltages along with new high-grade WIMA polypropylene film capacitors. 

BEFORE 

AFTER

AUDIO NOTIZEN