Black touch-up paint

[Gregory]

It may seem like this topic is a heist of Rick's chassis post, but the content was generated on Dec 12th when the 2205 was being reassembled after the power meter, cabinet and varistor servicing.

Here are a few sheet metal and aluminum touch-ups that should be addressed. Some are minor and others are SERIOUS. Let's start with minor chips such as on heatsink covers and edges. The following pic is a heat sink cover about to be dabbed with a Sharpie pen:

MC 2205 heat sink cover chip about to get dabbed with a marker pen. Another spot is visible in bright light, but better that a glaring scrape.


Using a Sharpie is a quick trick and hides some 'spot chips' but doesn't blend all that well. You can get away with it but marker ink doesn't protect much from oxidation.


Heat sink cover

Here is the right-rear heat sink cover where rust has started to form in the upper corner. A swab with auto polish has been run around the inside edge and about to be wiped/polished. Suppose all of the covers could be treated, or some paint brushed in there to preserve.

MC 2205 rear heat sink cover being treated with auto polish. Rust had formed in the upper corner where the paint had worn off. A marker pen dab is also visible.


Meter cover rust

Another problem was found, well know before but the extent of it wasn't obvious. Heat from the METER LAMPS softens the adhesive-backed foam rubber pads that hold the front PCBs in place. When they get HOT, the glue softens and they skate around (on each other) like layers of a cake.

Meter cover of MC 2205 showing old and deteriorated FOAM pads that hold the FRONT PCBs in their sockets. These pads shift around with heat and become misaligned.


When the pads were removed an ugly mess was exposed. The adhesive must trap moisture underneath or contain chemicals that attack the paint and metal.

Festering rust spots were discovered under the Meter Cover foam tape pads. This is a problem as it's in need or paint.


What an ugly mess!! :sigh: This is a cancer that must be fixed. The process would be to remove the adhesive with a Goo Gone type product, being careful NOT to disturb the McIntosh decals. Then remove the rust and prepare for touchup or spray paint.

Close-up of RUST that formed under the 2205 Meter Cover bottom edge. Yes it is UGLY with orange and blue spots!!


What paint to use

So the question is.. what type of paint can be used to touch-up these spots? Going further, what paint should be used to dab on nicks? and to mask and spray entires surfaces?


-Gregory

 

[dewickt]

The problem I run into is that I have seen McIntosh in flat, semi gloss, and polished high gloss black. One trick that works well for smal to large area repaint is Krylon BBQ & Stove paint, it is a fairly good match for the flat or semi gloss black and with careful waxing can be made to match the original paint. The one thing I like with it is after a few days of hardening it can be waxed to a high gloss, a bit of work but worth it on many of the older tube amplifiers like the 30s and 60s that through the years have been polished/cleaned to a beautiful high gloss.

 

[c_dk]

When I was heating up the power transformer case for my MC2250 to remove the core I needed to help the hot plate along with a plumbers torch. In the spirit of Terry's BBQ paint what Mac must of used was a hi temp paint because it did not burn off and peel like I expected it to. Pics in DIY.

 

[Gregory]

It's embarrassing to have posted those marking pen photos, but that's what I've been experimenting with for a while. I think it has limited use, and can hide some glaring bare metal marks pretty well (like bright aluminum showing through paint) but on close examination or in bright light, it doesn't look too good. It's really a woodworking trick. That stuff scratches off metal and can be removed if necessary.

What about using an airbrush? google.com/search?q=air+brush

The metal case of the B&K Audio Sig Gen < photo of B&K 3050 > was completely repainted with Rust-oleum Smooth Satin spray paint in the shade of `Fossil´ and came out quite well, but it took days to dry completely, maybe a week of two at room temp. How it comes out depends a lot on the prep work. The original screws were replaces with stainless. :yes:


-Gregory

 

[MX117.MC7150]

If your paint is taking that long to dry it likely means that you have not mixed it well enough prior to spraying. Some cans of paint sit around for years before being sold. Takes a great deal of shaking to get them well mixed. When I worked where we had a machineshop we used to chuck the can in a lathe and run at 10 or 15 rpm for an hour or two. Much easier than shaking by hand. Now I set the can on the heater to warm it up before using. Mixes better and dries faster.