McIntosh MR78 Cleaning

[dfontalbert]

Nice Job! It is unbelievable how good these tuners sound.

[Vintage Pete]

Very nice Job. I love my MR78...and yes it is remarkable how they sound. All in all I don't think one can do much better.

[Pampero]

Great tutorial, Pete. Now I know what to look for in an MR78!

[niconoise]

Hey Pete,
Inspiring job!
I am working on my MR77 and was wondering exactly how you cleaned the dial glass?
I have an older model than your MR78.
Thanks.

[niconoise]

The tape at the end of the dial glass had been coming off. It looks like black masking tape. I needed to clean the residue. I tried Goof Off. I wet the tape area and let it sit for 30 minutes. I tilted the glass so the Goof Off only stayed at the residue end. It did not work, that residue is tough.

MEK cleaned the residue and did not affect the print bullseye under the tape.
I needed to clean a film on the glass (on the back side) so I used denatured alcohol on a Q tip, wiping gently. It cleaned the film off and all seemed well. The numbers and scale seemed well attached. I put it aside to dry for 30 minutes and then wrapped it in a microfiber cloth. The next day when I opened the cloth to reinstall the dial I found that the dial scale had become detached and broken into fragments.

(I cannot attach a picture)

It seems the dial scale may be a decal. It feels thinner than the numbers which I assume are paint. It seems perhaps the decal adhesive was removed by the alcohol? It happened only at one end, the Goof Off end. Is it possible that the Goof Off crept up the panel? Anyways, I ordered a new dial scale.

[crwilli]

I might suspect the MEK (methyl ethyl ketone) vapors are the culprit but who knows, there might be something volatile enough in the Goo Gone...

[Vintage Pete]

niconoise....Wow, I'm sorry I didn't see your post of 5/20 for some reason. I've never used goo gone on my dials but that's a really mild product and I wouyld not suspect this would be the culprit. I'm not familiar with the other product you tried but I would not recommend using any solvents on the dial. I've always just used windex or similar product (armor all glass cleaner is also good) and a soft paper towel such as Viva. I might use an air duster spray to remove any fibers from the paper towel. At any rate, I don't think the dial scale on the MR78 (or similar vintage McIntosh tuners including the MR77) is a decal.

I'm really sorry to hear this....you might try Audio Classics for a replacement dial glass; I've seen them turn up on eBay from time to time as well.

[sllee]

Hi Pete,

Please enlighten me whether mr78 tuner is unable to operate in stereo mode if the stereo indicator bulb was blown/burn off?

Currently my mr78 always work in mono mode. If it is not working if it was turn to stereo mode. Please enlighten me whether replace the stereo bulb will solve this issue? Do you what type of bulb needed?

Apart from the above, do you have the code or model of festoon bulb which fixed on both side of dail indicator?

Many thanks in advance.

[Vintage Pete]

Originally Posted by sllee

Hi Pete,

Please enlighten me whether mr78 tuner is unable to operate in stereo mode if the stereo indicator bulb was blown/burn off?

Currently my mr78 always work in mono mode. If it is not working if it was turn to stereo mode. Please enlighten me whether replace the stereo bulb will solve this issue? Do you what type of bulb needed?

Apart from the above, do you have the code or model of festoon bulb which fixed on both side of dail indicator?

Many thanks in advance.

sllee....your MR78 should still operate just fine in stereo mode even if the indicator is burned out. It is only an indicator....fortunately they don't burn out often. In the 24 years I've owned my MR78, I've only replaced it once.

The stereo lamp is McIntosh part number 058-042. It is a pigtail lead type lamp. You should be able to get one by calling McIntosh labs in Binghamton or Audio Classics in Vestal, NY.

The festoon dial lamps are McIntosh part no. 058-032. Once again you should be able to obtain these lamps from McIntosh Labs or Audio Classics.

I hope this helps and good luck!

[mghorayeb]

This was an excellent and inspirational post. I wanted to dismantle my MR78 to look into the bubbling. I ended up changing the festoon lamps, foam, and most importantly repairing some substantial bubbling in the lower right. Fortunately, the bubbling didn't encroach on any of the graphics except for the "panloc" graphic. I carefully scraped off the offending ink, and then painted over with glossy black Rustoleum, several coats. Looks like new again. Can't upload pics, possibly cause I'm new here. Thanks Pete!