YAMAHA CA-610 II Stereo Integrated Amplifier, Professionally Serviced, 1970s MIJ

Yamaha CA-610 II, integrated stereo amplifier, made in Japan circa 1977-78. Professionally serviced, all functions tested and passed. Cosmetically good with no significant issues.
Ships worldwide. The package will be large, heavy, and delicate, so shipping may be a significant added expense. Estimated cost of international shipping is based on shipping to Australia, the furthest distance from my location. Please inquire for an estimate to your specific location outside of the USA.

Technician's notes: Yamaha CA-610 II, 5/10/20
-Used multimeter to inspect for short circuits between B+ and B- rails in power supply
-Replaced shorted 10,000uf 50v filter capacitor with Nichicon at a higher temperature stability rating of 115 Celsius
-Upon first testing, unit was not coming out of protect mode
-Placed jumper across both channels of speaker output relay terminals, to effectively bypass the protection mode (for temporary troubleshooting)
-Slow powered on unit using a current metered Variac and measured a high rate of current increase at low voltages
-Removed jumper wire from relay, one channel at a time to find whether one or both channels contained a short circuit, and determined that only the left channel was shorted
-Junction tested all transistors in left channel and replaced 4 shorted transistors in amplifier driver stage and 2 open current source transistors
-Used schematic diagram to find resistors that were likely to become misvalued when driver stage transistors blew
-Measured suspect resistors, and replaced 6 open resistors

-Junction tested all output transistors: good!
-Measured ESR of all audio caps: good!
-Checked audio caps for hard shorts: good!
-Junction tested bias diodes: good!
-Measured all emitter resistors: good!

-Powered up unit, and it came out of protect mode and both channels worked.

-Cleaned all controls and switches
-Resoldered output transistors, and voltage regulators
-Resoldered any sub par solder joints on main PCB
-Cleaned fuses and tightened fuse holders

-Checked thermal stability of differential transistor pairs.
-Metered quiescent current through 8 ohm dummy loads to ensure proper amp channel biasing
-Checked DC offset voltage
-Ran stereo sine waves through Leader LBO-508A oscilloscope to inspect waveform and check level matching
-Measured total harmonic distortion using Leader LDM-170 distortion analyzer, measuring .05% harmonic distortion in both channels
From the owner's manual: Continuous Min. RMS Power (both channels driven at rated distortion, 20Hz-20kHz):
50 + 50 Watts at 4 Ω
40 + 40 Watts at 8 Ω
Total harmonic Distortion: 0,05% or less (rated output)
Intermodulation Distortion: 0,05% or less (rated output)
Power bandwidth (IHF, both channels driven): 10 -50 ,000 Hz
Damping factor (8 Ω, 1 kHz): better than 50
Output Terminals: A, B or A + B (front panel switch)
Speaker Impedance:
A or B : 4 to 16 Ω
A + B : 8 to 16 Ω
Frequency response (Aux to Sp. Out): 20 Hz - 20,000 Hz +0,2 -0,3 dB
RIAA Deviation: 20 Hz - 20,000 Hz ±0,3 dB
Signal-to-noise Ratio (IHF-A network):
Aux to Sp. Out : 90 dB
Phono to Sp. Out : 75 dB
Residual Noise (Pre + Main Amp , 8 Ω): 0,4 mV
Input Sensitivity/Impedance:
Phono : 2,5 mV/50 k Ω
Tuner, Aux tape PB ( 1,2) : 150 mV/50 k Ω
Phono Dynamic Margin (1 kHz,0,1% THD) : 150 mV/1 k Ω
Output Level/Impedance:
Tape Rec Out (1, 2): 150 mV/1 k Ω
Tone Controls:
Bass : ± 12 dB boost/ cut at 50 Hz
Treble : ± 10 dB boost/ cut at 10 kHz
Loudness Control (volume -30 dB): 50 Hz : +9 dB, 10 kHz : +5 dB
Subsonic Filter: -3 dB at 25 Hz (12 dB/oct)
Audio Muting: -20 dB
Semiconductors: 4 Ics; 29 Transistors; 13 Diodes plus 3 Zener Diodes;
Power Source: 110/130/220/240 V AC switchable, 50/60 Hz
Power Consumption: 105 Watts