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MC30 Restoration -- Preservation First! (and caps)

Discussion in 'McIntosh Audio' started by sjfloat, May 13, 2017.

  1. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    Oh my...

    I have a couple of MC30s to restore. I don't know when I'll get the opportunity to dive into this. But looking in on them, I was appalled at the extent to which they had degraded. I live in a relatively humid region and my first concern is to clean up the exteriors and take whatever steps I can to prevent them from declining further.

    I've attached photos of one. Please assume the other to be in a similar state.

    So how should I proceed? The lettering is all more or less intact. How do remove the grime safely? And what, if anything, can be done about the rust? I have read one recommendation that one use a *dry* cloth only. But I think perhaps these are too soiled for that. And then, what can be done to arrest continued deterioration?

    I also have a question about filter caps (should that be another thread?). My intention years ago was to simply detach the cans and install good quality axials underneath. But these have become a bit more scarce now. Maybe it's a not a good idea in terms of value retention.

    What would you do if these were yours?*

    Thanks for all suggestions, comments and aid!

    * In most cases, it might be advisable to pretend you have less discretionary cash than you do. :)

    front.jpg top.jpg top-detail.jpg back.jpg left.jpg right2.jpg front-iso.jpg
     
    Last edited: May 13, 2017
  2. MACKIE1975

    MACKIE1975 Active Member

    Messages:
    374
    There is a New (re-manufactured) MC30 chassis on the auction site that you can purchase now
     
  3. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    21,464
    Location:
    Angel Station, Alabama
    I would carefully dry dust them with brushes after removing tubes first, then perhaps a gentle cleaning with a damp soft cloth followed by WD-40 and a soft cloth. Crusted rust spots may respond to a brass brush, but also produce some scratches from the rust particles. This may or may not get most of your chrome finish back.
     
  4. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    That sounds safe, maybe I'll start with that. Actually, the photos were taken after a brushing down with a dry natural bristle brush. But a damp cloth seems benign enough and WD-40 sounds like it might be beneficial.

    I assume you mean the non-lettered areas, right?
     
    Pio1980 likes this.
  5. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    I just remembered that I happen to have some Never Dull waddings. I wonder if that might be the ticket, if I was careful to avoid the lettering. I've also heard good reports about using aluminum foil; that it's actually a chemically assisted means.
     
  6. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    21,464
    Location:
    Angel Station, Alabama
    Right. Light cleaning there.
     
  7. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
  8. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    Applied a little WD40, didn't really even rub at this point; mostly just dabbed it on.

    front1.jpg

    I can see that this is going to be a challenge.

    top-preamp-tube-sockets2.jpg

    Note that the large blob show here is not rust but some kind of adhesive goo.

    top.jpg
     
    Last edited: May 13, 2017
  9. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    21,464
    Location:
    Angel Station, Alabama
    WD-40 is good for cleaning off adhesive label and tape goo. Otherwise, Goo Gone.
     
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  10. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    Good. I didn't really attempt to wipe off any excess. I'm just letting it work for a while. I may try the aluminum foil thing on the edges. Or the brass brush, I think I must have one somewhere.
     
    Pio1980 likes this.
  11. MikeRam

    MikeRam Active Member

    Messages:
    155
    Location:
    Portland Oregon
    I have a MC2100 that I'm working on that was a rust bucket when I first got it. I'm using Loctite Naval Jelly and it is slow going but it seems to be removing the rust. So far, it has not done any damage to the lettering either. I don't know if the lettering on the MC2100 and the MC30 are the same, but if you decide to try the naval jelly, test it on am more inconspicuous spot. The only real problem is that the pitting caused by the rust is still there. I don't think I can do anything about that.

    Don't use a brass brush as it will scratch the chrome. If you have an area that needs more elbow grease, use fine steel wool. I used the steel wool on the edges and it did OK.

    Mike
     
  12. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    Thanks for sharing your experience. I may give that a try. I've heard others recommend it too.

    This seems counter-intuitive to me. I would expect steel wool to damage chrome sooner than brass, the latter being softer. I believe chrome itself is pretty hard, but I think it's also extremely thin.

    If I use any metal scrubber, I am leaning toward trying aluminum foil on the edges. My understand is that it's less about abrasion and more a chemical thing. I'm going to see if I can find any more technical information about it.
     
  13. bcarey13

    bcarey13 Back to Basics Subscriber

    Messages:
    279
    Location:
    Sturbridge, MA
    I would never ever use steel wool, no matter how fine on McIntosh Chrome. You'll just create lots of scratches. Even those Never Dull wads if rubbed hard enough can scratch the Chrome
     
  14. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    21,464
    Location:
    Angel Station, Alabama
    Spotting rust jelly with a cotton swab might be the best procedure on the crusty spots, followed by spot rinse wash as recommended by the mrgr.
     
  15. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    I tried the aluminum foil a little bit in a less conspicuous and particularly bad place in the back on the edge. Very lightly, I'd barely call what I did rubbing. No miracles, but it's definitely better where I applied it than it was. As best I understand it, there is a chemical reaction where the aluminum itself oxidizes stealing oxygen from the iron oxide under the chrome resulting in something that's more easily removed, but IANAC*. Also, I believe there *is* an abrasive aspect but that it's microscopic, much finer than anything like steel or brass wool. I'm also shying away from the Never Dull. I may try a little naval jelly on a swab near the lettering, but if I do I intend to be very careful not to leave it on too long. Their own labeling says not to use it on chrome. I've heard mostly good reports with the naval jelly, but also one or two bad ones. I'm afraid the lessor of evils is all that's left to me at this point.



    *I Am Not A Chemist
     
  16. mnmmt

    mnmmt AK Subscriber Subscriber

    Messages:
    62
    Wenol, a micro fiber cloth, and lots of rubbing (turn the cloth often so the rust bits don't scratch the chrome) did wonders for my 250 chassis. The pits in the chrome are still there, but the rust stains are gone. I put carnauba car wax on after. Looks good for 50 years old.
     
    bcarey13 likes this.
  17. MACKIE1975

    MACKIE1975 Active Member

    Messages:
    374
    Buy a power toothbrush
     
  18. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    Thanks, another product to consider. Did you take particular care to avoid the lettering with this?

    I'm going to assume that all metal polishes are at least mildly abrasive.

    Brilliant! I probably have one somewhere already.
     
  19. MACKIE1975

    MACKIE1975 Active Member

    Messages:
    374
    Just put some painter tape over the sensitive area before apply any chemical or cleaning
     
  20. sjfloat

    sjfloat Well-Known Member

    Messages:
    621
    Location:
    Greater Pittsburgh, PA
    I plan to do just that. But it's going to be tedious. There's letter covering large areas.

    right1.jpg

    I expect I'll be doing a lot of taping and re-taping. Taping to get in between lines of text is going to be intricate. But I guess that's the job.
     

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