McIntosh replacement glass problem

Discussion in 'McIntosh Audio' started by genewoodall, Sep 26, 2014.

  1. genewoodall

    genewoodall Active Member

    Messages:
    117
    Location:
    Austin, TX
    Hello All:

    I recently had a refurb done on my MR 78 tuner at an authorized McIntosh Service facility including new factory glass. I was disappointed to see that the new factory glass will not pass light and illuminate the lettering above the controls. None of the control titles (volume, sensitivity, muting etc ) will illuminate. Numerous letters below the control titles do not illuminate including anything below Selectivity or Volume.. Stereo, Filter, Muting and db (upper left faceplate) are quite readable. I inquired about this and was informed by the service center that the new McIntosh replacement glass had a different ink formula and that the lettering was narrower than the original glass. I asked if McIntosh knew about this and was informed that they did, blaming it on “artwork” and that they were working on it.
    .
    I removed the front panel assembly and shined a flashlight from behind and even that strong light failed to come through the lettering I mentioned.

    Has anyone heard of or experienced this. I emailed McIntosh about it and never got an answer.

    Thanks
    Gene

    MC7200, C30, MR 78, MAC 4275, MC2120, VA Beethoven, McIntosh XR7
     
  2. c_dk

    c_dk Addicted Member

    Messages:
    5,498
    Location:
    West Michigan
    Is the diffuser is in backwards......we have all done it. The opening of the "cone" hole goes towards the bulb. Why don't you let the tech make it right?
     
  3. AuburnM5

    AuburnM5 New Member

    Messages:
    31
    Sounds like a diffuser issue to me, not glass. I had a MC2255 with a broken diffuser, unfortunately they were no longer produced, so I just had to deal with it. Same problem as you. Meters lit up fine, but the control panel did not.
     
  4. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,750
    Location:
    France
    Hello genewoodall

    Has anyone heard of or experienced this. I emailed McIntosh about it and never got an answer.

    YES , this is true ! I know this problem on every MR78 glass replacement made for the last 5 years .....

    The only way to cancel this problem is to take off the resistor of 2 ohm /5w . If you make some measurement of the lamp voltage you will not find 6,3V but less ! once to take off this resistor the voltage increase a little bit and you will see the light from all front panel lamps going much better .
    Again you have to think about what you are doing ! make this mod is not normal and the unit is no more like it was before .....:scratch2:
     
  5. genewoodall

    genewoodall Active Member

    Messages:
    117
    Location:
    Austin, TX
    Jumping the resistor no help

    That was done. No help. I tried brighter bulbs (#44) but no improvement over the stock bulbs. Again, a powerful flashlight will not illuminate the lettering.

    Thanks
    Gene
     
  6. jlovda

    jlovda Things I loved from the 60's and 70's

    Messages:
    3,129
    Location:
    NE Ohio
    If you attached the diffuser to the back of the glass with strong double sided tape and misaligned it, you're screwed. You will ruin the paint on the glass if you try to pull the diffuser off. This is why fixing bubbles in the glass is mostly impossible. Aligning the diffuser behind the glass with the tape ready to be stuck is tricky. The lettering is on the glass and a matching frosted white rectangle is on the diffuser. If the white rectangle is not perfectly centered behind the lettering, the top or bottom of the word will be dark. Use the thinnest double sided tape you can find. The appearance of the lighted letters looks best the closer the diffuser is to the glass.
     
  7. 62caddy

    62caddy Trust but verify Subscriber

    Messages:
    8,168
    Location:
    NEPA
    If a powerful flashlight will not shine through the lettering with the glass off the unit & in your hand, there is definitely something wrong with the way it was printed. All the diffusers in the world won't solve this problem - no matter which way installed.

    You should call McIntosh directly. (607) 723-3512
     
    Last edited: Sep 27, 2014
  8. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,750
    Location:
    France
    McIntosh MR78 Light problem

    Hello 62caddy !

    Nice new avatar !

    If a powerful flashlight will not shine through the lettering with the glass off the unit & in your hand, there is definitely something wrong with the way it was printed.

    This is perfectly true ! I can't believe that factory supply you a "poor quality glass" !
    If you see through the glass with the daylight , does your "letters" appears or not ??

    I think there is another possibility : you place the diffuser on reverse ....But I can't believe you did not double check
     
  9. genewoodall

    genewoodall Active Member

    Messages:
    117
    Location:
    Austin, TX
    Diffuser ??

    I just removed the glass assembly for the nth time. One end of the diffuser has 10 tic marks than could line up with 10 tic marks beneath VOLUME plus there is a piece of tape that looks like it would illuminate the 'OFF'. If that is so then the diffuser is reversed. The circle of tic marks is over SENSITIVITY.

    The conical shaped holes at the bottom have the larger side out.

    Anyone know the correct orientation of the diffuser?

    Thanks Again
    Gene
     
  10. 62caddy

    62caddy Trust but verify Subscriber

    Messages:
    8,168
    Location:
    NEPA
    There are only two ways the diffuser can be installed.

    If you cannot get light to shine through the nomenclature when holding it up to the sunlight or with a flashlight, the problem is not related to the diffuser, lamp bulbs or diffuser orientation.
     
  11. Classic_CJ

    Classic_CJ Well-Known Member

    Messages:
    583
    *** If a powerful flashlight will not shine through the lettering with the glass off the unit & in your hand, there is definitely something wrong with the way it was printed. All the diffusers in the world won't solve this problem - no matter which way installed. ***

    I'm totally with 62caddy on this-- I believe you've gotten a defective glass. And as c_dk mentioned , the correct orientation of the diffuser is with the wider part of the cone-shaped holes facing out. But this doesn't sound like a diffuser problem to me.

    Hint for anyone out there changing a glass for themselves-- before you install anything, hold the glass up to a good light source (for example, I use the fluorescent ceiling lights in my shop) and not only be sure the lettering shows, but look for any small holes or other black paint defects in the glass. It does happen! If I find any pinholes, I usually just re-touch them with paint rather than return the glass, but if the lettering doesn't show, it would go back. To date I haven't seen this problem, but it's also been a few years since I changed any MR78 panels.
     
  12. genewoodall

    genewoodall Active Member

    Messages:
    117
    Location:
    Austin, TX
    Here is a phota

    OK guys. Let me back up just a bit. Holding it up to a window in sunlight--nothing. Holding up to a 3 LED 9V flashlight (the kind with a battery like a small brick) a very faint light. Holding it to a 100 bulb, which I just did, does show some faint light.

    Photo enclosed. The orientation of the diffuser looks flipped end over end to me. Note the 10 square boxes that I think would go over the 10 tic marks at the volume control are at the wrong end of the glass if indeed their purpose is to illuminate the tic marks.

    Anyone??

    Thanks Again All
    Gene
     

    Attached Files:

  13. c_dk

    c_dk Addicted Member

    Messages:
    5,498
    Location:
    West Michigan
    Yes it looks like the difuser needs to be flipped. The difuser is like a light pipe and the white reinforces the light behind the lettering and such.
     
  14. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,750
    Location:
    France
    MR78 trouble with lighting

    Hello GENE !

    Look carefully your picture ......You can see all the little white square on the right of the diffuser ?
    You place it on the wrong side ! all these square should coincide with the mark of volume level visible on the outside of the glass !!

    You are not the first one who did it wrong don't worried but I did not see really the factory making a bad glass ....
    Be very carefull when you will pull it from the rear of the front glass , be gentle to avoid to dammage the "black" ink of the front panel ....

    Once you will place your diffuser on the right way , you will see your "green letters" lighting on !!
     
  15. 62caddy

    62caddy Trust but verify Subscriber

    Messages:
    8,168
    Location:
    NEPA
    Oh boy - never occurred to me all this time you were looking at the glass with a flashlight with the diffuser attached already! :stupid:
     
  16. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,750
    Location:
    France
    MR78 trouble with lighting

    Gene

    For you and only for you

    Here are some picture of one MR78 Front glass and diffuser well placed :thmbsp:

    I have 6 MR78 here for repair so no problem for take one front panel off to make a picture :yes:

    you have now closer pictures of left and right corners !
     

    Attached Files:

  17. mark506

    mark506 Active Member

    Messages:
    104
    Location:
    Worthington, Ohio
    Classic CJ: What kind of paint have you used? I have a very small pin hole on my MR 74 glass.
     
    Last edited: Sep 27, 2014
  18. CountD

    CountD Super Member

    Messages:
    1,243
    Put the diffuser on correctly and just be happy that they still make the glass.:thmbsp:
     
  19. CountD

    CountD Super Member

    Messages:
    1,243
    Like Terry has always said, buy black Rustoleum and glob it on there with a brush. Let it dry for three days and put it back on. Has worked at least 10 times for me.
     
  20. Classic_CJ

    Classic_CJ Well-Known Member

    Messages:
    583
    I use the Testors brand hobbyist paint in the little bottles that one typically uses for model airplanes and such-- little to moderate dab'll do ya over the pinhole, with a small, soft brush. And, if Terry says black Rustoleum, he da man, so also fine by me.

    I've used regular old Krylon spray paint to restore a number of glass panels that had severe bubbling or peeling along the edges. You have to gently scrape the loose paint off the glass (I use a small plastic screwdriver) back to where it still sticks, mask off what you don't want sprayed (without adhering anything to the good black paint, and that's the tricky part!) and spray several coats. (A single coat will not be thick enough to block light).
     
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