McIntosh MAC1900 Vintage Receiver - Rare Survivor Condition

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This is a Super clean classic MAC1900 in what we call rare survivor condition.

Most MAC1900's suffer from having spent time in someone's damp basement, resulting in light rusting or pitting.

Not this one! The chassis is super clean, and more importantly the faceplate is near perfect. And we never throw around the word perfect unless there's good reason.

We recently completed a full service on this example, replacing a handful of components as shown in one of our photos towards the end.

The MAC1900 is quickly becoming a great collectible piece, mostly due to ts great features, solid tuner section, and amazing looks.

Best of all it includes the original owner's manual, service manual, AND the schematics. A great find!

Service Notes:
• Thorough internal & external cleaning
• All controls cleaned and lubricated
• Faulty balance control replaced
• Any out of spec capacitors replaced
• Any burnt out lamps replaced

Test Notes:
This is a vintage unit and has a small quirk. The volume balance is slightly off. This is evident on a scope, but would not be noticeable during casual listening. When the volume control is rotated fully counter-clockwise (0), sound can still be faintly heard.

This piece passed our routine bench power tests; and all functions, including AM/FM tuning, were tested and confirmed working within manufacturer specifications.

The SkyFi Testing Process for Receivers:
We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and transistors are checked for signs of stress or damage.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally, we run the receiver to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If everything reads clean, we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The receiver then remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will be also be tested.

Then the tuner is thoroughly tested in our lab utilizing our professional Sencore SG80 FM Generator, which allows us to generate a reference FM signal of any frequency and amplitude, and then measure the resulting tuner output on our Sencore PR81 or oscilloscope.

Final testing involves pushing actual music thorough the receiver. We've learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage KEF speakers that we're very familiar with which quickly reveal any discrepancies. Some receivers will then move into our listening room where they are tested with our in-house reference speakers of choice.

Original MAC-1900 Owner's Manual

Original MAC-1900 "If You're a Hurry" Guide

Original MAC-1900 Service Manual

Specifications:
Tuning range: FM, AM
Power output: 55 watts per channel into 8Ω (stereo)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.2%
Damping factor: 50
Input sensitivity: 2mV (MM), 250mV (line)
Signal to noise ratio: 76dB (MM), 90dB (line)
Output: 250mV (line)
Speaker load impedance: 4Ω to 16Ω
Semiconductors: 3 x IC, 53 x transistors, 39 x diodes, 4 x thyristors
Dimensions: 15.99" x 5.51" x 15" (406 x 140 x 381mm)
Weight: 33 lbs. (14.97kg)
Finish: Black and gold anodized front
Years: 1972-1975