McIntosh MR78 Cleaning
 

Per Dan's ("jdandy") suggestion I have chronicled the disassembly and cleaning of my beloved MR78 Tuner. Since there are quite a few photos, (over 40) I'll have to do it in installments, with the first installment tonight.
I'm off to a later start than I had hoped as I'm having a computer issue that took up some time tonight. I'll start with the removal of the front panel and dial glass. Pardon some of my close ups aren't the clearest...


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The tuner's knobs and felt washers.




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Lower panel phenolic light shield.



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The foam light seals, which I replaced a few years ago, are a bit of singed from the heat of the dial illumination festoon lamps. But, they aren't disintegrating and overall not in really bad condition. I decide not to change them out this time.




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One of the dial glass mounting brackets, and its dial edge color filter, which came off in pieces due to heat deterioration.



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Stay tuned for next installment......


Pete

Part two-replacement of dial edge filters
 

With the dial glass nice and clean, next we replace those burnt dial glass edge color filters, and carefully reinstall the dial glass using the small brackets. This part is a little tricky.


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The old and the new.....



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The new edge filters are creased along their length prior to installation. They should be creased to achieve a 90 degree bend.



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Small strips of tape are used to seal up the openings at the top to keep the light where it belongs and maintain brightness.



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New festoon lamps at the ready....





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New festoon lamps installed, and the tape strips at the top of each lamp area closed up.




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Now let's see how the dial illumination is looking...looking good!




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Next we replace all of the lower panel illumination lamps using type 1866 bayonet lamps.


We're almost done with the front section of this beauty....stay tuned!



Pete

With the front panel glass cleaned up, we'll temporarily reinstall it for a sneak peek at how things are looking so far.....


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Looking pretty nice!



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Next, we turn the unit over and remove the bottom cover, so we can access the screws that hold the upper cages on. These have to come off so we can clean the top of the chassis and circuit boards.



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Note the dust on the top side...



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Another view showing the dust on the Bridge discriminator and FM detector.



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We use a combination of a small camel hair brush and air duster spray to clean off the Multiplex PC board.



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Then the chassis is cleaned up, and the discriminator enclosure and FM detector is cleaned up and polished using a fine coat of household oil.



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A slightly closer view.



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With the large cage reinstalled, we repeat the process on the other side, where the IF PC Board and its RIMO filters are located. Note the dust.



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The IF Board and filters are cleaning up nicely.



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Next, the meter lamps are replaced with type 1847 bayonet lamps, as well as the color filter tubes. For a shot like this, we have to be careful not to touch the live lamp sockets to anything, causing a short! The unit was plugged in and turned on for the photo only.


We're almost done, stay tuned for the next installment....


Pete

With the Front end, chassis and circuit boards cleaned, and all lamps and filters replaced, we're ready to reassemble the Tuner. A fine coat of oil has been used to polish all of the painted metal surfaces. The chorome chassis has been cleaned with a soft cloth moistened with glass cleaner. Cotton applicator swabs are used to clean tight areas on the top of the chassis. The knobs have been cleaned an polished.

Next we reinstall the bottom cover...


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The front panel is reinstalled....


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Hope you've enjoyed following along with my little project. Very shortly I'll be doing the same thing with my MR77. :yes:


Pete

Pete.......This is exciting. Your pictures immediately brought back memories of cleaning my MR74. Your photos are looking good.

Pete,

You are a brave man. Looks GREAT!:yes:

Thanks Mike...I've done this quite a few times. In checking my records it's been longer than I thought since I replaced the foam light seals. I'm thinking I may go back in and replace those as well...

Stay tuned...

Pete

Look Out! He's going back in. :D


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:whistle:

:lmao: :lmao:

Okay Dan, installment two is up! :yes:

Pete