Yamaha CA-810 Integrated Amplifier
Today were showcasing a customers Yamaha CA-810 Integrated Amplifier we restored. The CA-810 was released from 1977 to 1980 with a nominal rating of 65Watt .05% THDN and as standard for Yamaha a two stage MC and MM phone input feature.
NA06873 Multi-Circuit PCB
The Main PCB NA06873 contains the regulated power supply, protection, meter control and both left and right driver assemblies with the TO-3 outputs on side by side heatsinks. Its worth noting original units will contain a large amount of caustic glue that oxidizes components, in this unit all effected components were replaced and glue removed off the PCB top plane.
The RIAA phono stage covers most of this assembly making adjustments awkward and cumbersome, all new precision potentiometers for both meter points, regulated 25V supply and bias points were re-oriented to the foil-side of this PCB for better access with test points added to each emitter resistor.
#800 Circuit Regulated -/+25V Supply & #600 Protection
The regulated supply is based off a simple bridge rectifier and establishing the -/+ AF stage rails. As noted above, all effective glue was addressed and removed. The protection consists of a DC deviation circuit.
Both TO-220 regulators were replaced with robust Fairchild modern TO-220’s with new performance Wakefield synthetic thermal compound applied. Remaining devices were replaced with modern, low noise TO-92 and TO-92L Fairchild devices for better dissipation. The Bridge Rectifier array was replaced with Ultra-Fast, Soft Recovery axial Vishay diodes. The 25V adjustment was replaced with precision Bourns potentiometer as described above.
The large decoupling and output coupling electrolytic were increased in capacity for better filtering and replaced with a low impedance, high temp (105C) Nichicon PW with an increase in operating voltages, as well as remaining electrolytic. Bipolar in the protection were replaced with VP Nichicon capacitors.
BEFORE
25V Confirmation
#700 Meter Peak
Housed on the same PCB, the peak to peak output is relayed via this circuit (calibrated in dB and designed to relay 8OHM loads). The electrolytic capacitors here were replaced with a low impedance Nichicon PW and VP Bipolar and WIMA PP bypass capacitors with an increase in operating voltage. New low noise Fairchild TO-92 devices installed and precision Bourns adjustment potentiometers as described above.
#800 Driver L/R
The driver stage utilizes a differential front end with a SEPP, complimentary OCL output and limiter stage.
The differential stage was replace with 1% matched low noise TO-92 PNP Fairchild devices, for better linearity the two were thermally coupled together. New pre-driver TO-126 and TO-220 driver devices were replaced with modern, robust Fairchild/On-Semi type with new performance Wakefield synthetic thermal compound applied.
Differential Boding
The electrolytic here were replaced with a high-grade WIMA polypropylene film type and low impedance high temp (105C) Nichicon PW type with an increase in operating voltage. New adjustment potentiometers were installed as described above.
BEFORE
AFTER
BIAS Confirmation
NA06872 Rectification & Tone Amp
The NA06872 PCB contains both Tone Amp and Filter controls but also the 12,000MFD filtering and rectification stage for the driver rails.
As part of the proper cleaning protocol the open-frame potentiometers were removed and D5/F5 Caig Lab products applied.
New high-grade WIMA polypropylene film capacitors and audio grade KT/KA Nichicons were installed with an increase in operating voltage. All small signal devices were replaced with a low noise modern TO-92 Fairchild type.
BEFORE
AFTER
The original filter capacitors were replaced with high quality computer grade type with an increase in capacity for better filtering and power reserve.
NA06874 MM & MC RIAA (Phono)
The RIAA stage has a unique construction compared to other CA series Yamaha’s. self contained and shielded, the NA06874 contains both a MC type amplifier and MM RIAA EQ stage with two separate phono inputs. The MC stage utilizes a unique low noise 5-pin IC 1G00164 and a FET type MM front end SEPP output stage.
High-grade WIMA polypropylene film capacitors were installed along with audio grade KT/KA Nichicon capacitors, low impedance and VP Bipolars were also employed. All small signal devices were replaced with low noise, TO-92 Fairchild devices.
BEFORE
AFTER
Lamp Modification
As highlighted below the meter lamps operate off rectified 36V supply, using simple math we can break down using custom 8V SMD lamps as, this also allows us to back off the dissipation evident on the original wire-wounds that marred the pcb; (Vs-Vf 12(Vf)) / i (.02mA) 600ohms 1+W (i[2] x 600 (.24mW)(backward:600xi(12Vf)
BEFORE
AFTER
AUDIO NOTIZEN
