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New to McIntosh, Tuner Issues

Freddie73

Freddie73

Active Member
I just purchased a Macintosh MR 74 off the auction site. Physically it is absolutely beautiful no rust no cracks in the glass. AM works great. FM has very little volume. I have to turn the amplifier’s volume all the way up to get sound, the red stereo light is not coming on. It was purchased as working as it should. It is not. I got it in a really good price. I have restored two Fisher tuners an FM-100B and a FM-200B and several receivers and integrated amps. I was hoping this would be plug and play. It’s not. How difficult and is it a deeper issue. This is my first McIntosh purchase.image.jpgimage.jpg
 
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Have you verified that the power supply voltages are all correct?

You might try removing the IF chip and cleaning the legs of the IC and the IC socket. Assuming it has a socket. Doing this made a world of difference on my MX113. I believe they are very similar tuners.

The IC chip should be under the long thin cover on the tuning knob side of the unit.
 
A few basic questions:
There is a set of fixed outputs on the rear. Is that the output you are using?
1769008437407.png1769008558184.png
Is Stereo muting off? Stereo filter out? Selectivity normal? Did you try FM Mono?
Are you using an antenna? (at least a piece of old wire)
 
The important part is that the unit has strong cosmetics. Far more difficult to correct and carries more weight on value. Operational condition can always be restored.

This side of documentation of recent repairs, always assume an older tuner will need servicing. I have never gotten a vintage Mc tuner/receiver than didn't need some level of attention unless purchased from a professional trusted reseller who guarantees the equipment they offer. Box it up and sent it out to Audio Classics. They'll have it working and detailed up like new again. Expect a tab around $300/+. Unless it was shipped in a newer McIntosh double box carton, it would be wise to order one. It might also be a good idea to remove the glass faceplate & knobs before shipping but I would check with them about this first as the dial may be needed for calibration.
 
Last edited:
Refugee said:
A few basic questions:
There is a set of fixed outputs on the rear. Is that the output you are using?
View attachment 3681174View attachment 3681175
Is Stereo muting off? Stereo filter out? Selectivity normal? Did you try FM Mono?
Are you using an antenna? (at least a piece of old wire)
Click to expand...
I don`t know which set of the tuner`s outputs that are connected, but the OP`s front panel picture shows the tuner`s variable output volume control`s knob pointer all the way down !
If that`s the case, then no surprise of very low FM audio output, however he did indicate the tuner`s AM`s output is normal, so never mind.
 
I have used fixed( volume control non functional) and variable with tuner volume and I have it connected to my Fisher 400 tube receiver thru the auxiliary imput ( I’ve used it with other SS tuners). This should work? I can try my Fisher x-100 tube integrated amplifier. Anyway I’ve tried FM mono/stereo, muting out/distant/local, selectively normal/narrow, stereo filter 1/2/and out. Tonight I used Deoxit on the antenna connectors and a new dipole antenna and volume pegged on the Fisher 400 with MR74 connected both fixed and variable (with volume pegged) I now am getting about 70 decibels.
Still no stereo light ( could be burnt out ) but everything works as it should but just low volume.
From what I’m reading it appears the mpx board needs recapping. I will eventually replace all the electrolytic capacitors.
What would you guys recommend for the Can capacitor? I’ve used Hayseed Hamfest for my tube equipment so far?
I agree it is in beautiful cosmetic condition and I will restore what I can and send it of for the rest and an alignment.
Any other suggestions are appreciated. This is my first McIntosh product.
 
Motnick I did find the IC it has twin IC’s. Both have 14 pins (# 002 274 544).
Are these soldered in or snap in. I do have a hot air gun/pen if recommended.
 
Freddie73 said:
Motnick I did find the IC it has twin IC’s. Both have 14 pins (# 002 274 544).
Are these soldered in or snap in. I do have a hot air gun/pen if recommended.
Click to expand...

In my unit, mx113, they were both in a socket. I was able to pull them, clean them, and reinstall without issue. That entire board on my unit had collected a lifetime of dust from the open vent cover.
 
You should repair the issue with the unit before you replace capacitors. If you are able to remove the IC chips and clean the legs and that fixes the issue I see no reason to replace them.

Are your chips installed in sockets?
 
Used Deoxit D-100 on switches then cleaned with CRC then Lubricant. I was able to get Hayseed Hamfest to make me a new Can Capacitor that is vinyl wrapped for a drop in replacement of original can. Think it looks cleaner. I have been too busy working to get into this beautiful tuner. Will post as I go along.
IMG_5683.jpegIMG_5682.jpegIMG_5680.jpeg
 
I did pull out the twin IC chips in the IF section. They were snap in . I removed and cleaned the legs and sockets. We will see.
 
This is the original opto-coupler. It is known as failure prone because it has an incandescent bulb inside. McIntosh designed a drop in replacement that uses an LED bulb.IMG_5782.jpegIMG_5786.jpegIMG_5782.jpeg
 
I am not getting stereo reception with MX114 and if I am not mistaken it has the same tuner section as the MR74. The stereo light flickers when I rotate the tuning dial but when tuned to a station the sound is mono and the stereo light does not stay illuminated. My MX113 works fine. What exactly did the opto-coupler fix?
 
Very, very low FM volume. With my amplifier pegged all the way to 10 about 60 decibels. Also mono only. Changed the opto-coupler and all back to normal. Receiving stereo and normal volume. I’ve already purchased replacement electrolytic capacitors for maintenance. If it has an original incandescent opto-coupler as the MR74 does it needs replacing at this time anyway and couldn’t hurt.
My opinion as it’s about 40-55 years old.
 
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