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McIntosh MAC1900

Solid State AM-FM Stereo Receiver (1972-75)

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McIntosh MAC1900


Tuning range: FM, MW

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: 406 x 140 x 381mm

Weight: 14.97kg

Finish: black and gold anodized front

Year: 1972


instruction/owners manual   English -

quickstart guide   English -

service manual (4X230 - AL9999)  English -

service manual (1X001)  English - salbreth1

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re: MAC1900

I had my Mac 1900 rebuilt last year at DeWick repairs and I just recently finally got around to hooking it up. After 3 or 4 songs played on my turntable the Mac 1900 made a click noise and shutoff. It would not turn back on for maybe 15 minutes. I contacted DeWick but he is on vacation till after February. Any ideas.

re: MAC1900


re: MAC1900

I'm actually writing concerning my Stereotech 1200 which was made by McIntosh and similar to the 1900 to some degree.

My issue is that I have a hum from both speakers which gets louder as you increase volume. The hum is present with nothing else connected to the receiver and it's not a speaker issue.

To me it sounds like the hum you'd associate with a poor ground. As well the hum greatly increases when a dimmer switch in the room is turned on.
No other receiver hooked up in the same place has this issue.

Any ideas for me here?
Thank you.

re: MAC1900

A fellow StereoTech owner! I bought mine in 1976 while I was service manager for a McIntosh dealer. The actual manufacturer was Fosters (Japan) under contract to McIntosh, as I recall they only made a few thousand pieces, so its a bit of a rare bird.
So much for the history lesson. On to your problem.
In your post, you state the hum increases or decreases with the volume control setting. This rules out an amp or driver circuit issue as the hum is present before the vol control. Since you never mentioned which input you are using there are several variables.
1st, disconnect all other equipment(except spkr's) connected to the rcvr, set to aux in and turn on. Is the hum still present? If so you have proved it to be the rcvr and not anything connected to it. Since the hum is present in both channels, the defect is one that has to be shared by both left and right channels, most likely suspect is power supply. If you have an oscilloscope, its a breeze to pick up hum on VCC buss lines, again suspect failed lytic's, after all this baby is 40 years old

If the hum goes away, start connecting all the other gear such as tape deck, Phono etc, one at time testing as each one is reconnected. it could be another piece of equipment or a ground loop introducing the hum.

Good luck with your troubleshooting, don't give up on that unit its worth keeping.

Steve Thomas

re: MAC1900

I'm not terribly audio savvy, and I was wondering if there is a recommended setting for the "load impedance" switch on my MAC1900 receiver. Thanks!

Amp Caps in MAC 1900

I find myself refurbishing this MAC which has been in the family since new in 1973. I would have thought the mian power amp caps would have gone by now.

WRONG! They are in really good shape! I took the Network Analyzer and plotted Z and they are still meeting the spec's for current day manufacturer data (CDE).


Thank you

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