MC2205 Love - Part 3

[pwhartman]

Great process of documenting the restoration - what a labor of love! Keep us posted.

I have a line on one of these amps, so it is good to see you going through this process. If I have any questions, I know who to ask!

Paul

[jdandy]

Gregory.......I am thoroughly enjoying this restoration. Your attention to details, and the photo documentation is interesting to follow. Thanks for sharing this with us.

[Gregory]

Originally Posted by pwhartman

Great process of documenting the restoration - what a labor of love! Keep us posted. I have a line on one of these amps, so it is good to see you going through this process. If I have any questions, I know who to ask!

Paul

Thanks for the encouragement, but the credit goes to the whole Mc community and their posts over the years. It's a distillation of all that material. I'll have to PM you on the CS3.7s as I've listened to them at a local dealer and the speakers themselves disappear, leaving a hologram-like sonic image in the room.

-Gregory

[Gregory]

A rather serious problem with the hardware

Another glitch in the power meter housing rebuild. Was in the process of drilling out the housing and rivet holes to #6 clearance holes and discovered there's no room for machine nuts on each end!! Here are some photos of the dilemma.


0.140" (9/64) clearance holes drilled for the reflector, brackets and housing attach screws.



The #6 screw fits just fine, however there's no room for a machine nut.



This is nearly a show-stopping problem. The metal is too thin to tap and the flange is too narrow for a nut.



An aggressive sheet metal screw could be used but we're right on the verge of destroying the holes.


Wrap-up

There are two choices that come to mind. Grind down a coupe machine nuts and fasten the screws with them, or run aggressive hex-head sheet metal screws (0.165 max, 0.100 min) in the holes, but the heads might be too high. SM screws usually go into aluminum parts ok, but I'm unsure about sheet metal. The holes are currently 0.140" dia.

HELP.. what to do now? The job is so close to being complete!!


-Gregory

[Gregory]

Lamp housing complete

The sheet metal of the housing was polished with Carnauba wax and MAN.. did a lot of BLACK tarnish come off onto the rag. You could spend an hour or two with a buffing wheel to make this piece glisten. It is very slippery to the touch now and protected from further oxidation due to the waxy sheen. All three foam strips were cut to 9/32" width (1/4" plus a 32nd) and I may replace the two end pieces with exactly 1/4".

The following is a pic of the completed housing with reflective backing and foam tape applied.


Restored lamp housing polished with Carnauba wax, reflective backing and strips of 1/8" thick rubber foam applied.


Foam products

Let's look at the foam products purchased for use on the MC 2205 refurb. The two packages on the left are Frost King Rubber Foam tape in white and black with a 5 year guarantee. The other two on the right are from Ace Hardware. The 1/8" thick black sponge rubber tape is being used on the "light box" or housing. The gray material is typical poly-foam weatherstrip that was the least expensive. Here are two samples of the black foam rubber selected


Some foam tape products for use on the 2205 front panel. Frost King on the left and Ace Hardware on the right.



The top strip is 1/8" thick x 3/8" wide sponge rubber. The bottom piece is 1/4" think x 3/8" wide rubber foam.


Kludge nuts

This section is called "kludge nuts" because two of the #6-32 machine nuts were ground down to 0.278 and 0.273 tip to flat. These nuts are actually too big for this assembly. A box of small width #6 nets would be better, but they are special order hardware. Here is a photo of the cut nuts.


Two stainless steel housing nuts cut down to fit against the walls. How's that for cutting your nuts off!? LoL



View of the ground #6 machine nut being tested for clearance.



Another view of the ground machine nut to hold the housing in place. I'm not too proud of this kludge.



Space is tight, but doable. Now you see why a tapped hole was used originally. McIntosh could have used a captive nut.


Wrap-up

The lamp box is finally complete but I've neglected to order the BLUE acetate film from Mc Parts, or any other supplier for that matter. Hopefully Mc can ship tomorrow for Friday deliver. The black sticky-tape holding the plexi-glass had loosened, so now a replacement tape will be needed. Yet another challenge.

Still having fun servicing the MC 2205 amplifier.


-Gregory

McIntosh owner for over thirty years.

[Gregory]

Front Panel Restoration

It's going to be a long weekend waiting for the last few Front Panel items/parts to arrive. The acetate films ordered from the factory are Azure Blue (092490) and Pale Blue (092250). The originals which are crunched, wrinkled and faded can be seen laid out in the following pic.


Original acetate filter films laid out on yellow felt material with meter chassis bracket sitting behind.


There is one flaw in the panel GLASS assembly that I could perhaps live with but it should be restored to make the unit look new. Maybe the answer is to purchase a new front glass panel? Notice the lettering just under the meters area in the photo below.


The gold lettering reads "STER VER AMPLIFIER." What's involved in fixing these letters? (please ignore reflection of hanging ceiling lamp)


Mounting nuts for lamp housing

The photo of the two light-box mounting nuts was embarrassing the other day, so I took the time to make them at least look `normal´ by grinding the opposite tips for an overall width of 0.225" and 0.228".. close enough for gvmnt work. Here is a photo of the reworked lamp housing nuts, as these two fasteners must hold the entire assembly onto the front panel.


Reworked lamp housing nuts. Notice the finish of the sheet metal after polishing with wax!!


Power Output PB Board shield

There was even time to futz around lubricating, and polishing other sheet metal parts like the shield inside the RIGHT driver board. The following is a picture of the shield polished with Carnauba wax and reinstalled with NEW 1/4" #6 stainless screws.


This view shows the polished right driver board shield, and both new and nasty old machine screws.


Even the Power Transformer screws were replaced with stainless. In the photo below you'll see where the old and yellowed screws were replaced. Stainless washers on the rear transformer braces were also added. Have ordered more #6 stainless hardware from McMaster including small 1/4" wide #6 machine nuts and internal-tooth lock washers.


A view of the sparkling 2205 amp which is almost DONE!! Note the replaced power transformer screws.


Patches on cut insulation

Some of the insulation on internal wires was cut, probably from the use of long-nose pliers when applying 90° bends at the factory. It's common practice to form wires into `bends´ and bundle/route them together. A simple solution was to attach tiny 0.10" wide x 0.03" thick tie-wraps to the cuts. They hold the insulation tight and can easily be removed.


Tiny tie-wrap applied to a wire where insulation was torn, this one in the LEFT final output wire.



Tiny tie-wrap applied to a wire where insulation was torn, this one on the center conductor wire from the input board.


Wrap-up

Hope you all are enjoying the views, tips and tricks of resorting an old and beloved McIntosh amplifier. As stated before, this is not a tutorial or how-to, but an open discussion and a photo journal of a VERY meticulous Mc amp overhaul and restoration.


How about one more photo for Mc Love. Look at the reflection coefficient of those waxed-up transformers. Wow!!


It has been most enjoyable.. but even more-so next week when the amp is operational.


-Gregory

McIntosh owner for over thirty years.

[Ron-C]

Great work now order up those new PS caps. You will hear the difference and yes there is a reason that these big caps have a life spec in thousands of hours. I am not talking about failure and hum but sound.

Thanks,
Ron-C

[Vintage Pete]

Gregory,

Your progress photos look really great. I think if I were you, and had gone this far, I would go ahead and get the new glass as well. That missing lettering is pretty common on this model at this age. When I got mine, I had no choice but to replace the glass, as it had become slightly damaged in transit, as you can see.

At the time (2003) Mac no longer had the screens for the glass, and engineering had to have new ones made, or ordered. Something like that. At any rate, hopefully you won't have a problem acquiring a new glass panel.

I don't think the lettering can be repaired, once it begins to separate. I also think I see a tiny bit of delamination of the black backing just starting around the headphone jack-another common problem with models of this vintage. I think Mac has essentially addressed this issue with the replacement panels.

I also replaced the blue color meter filter wth a replacement piece from Mac.

Pete

[Gregory]

Originally Posted by Vintage Pete

Gregory,

Your progress photos look really great. I think if I were you, and had gone this far, I would go ahead and get the new glass as well. That missing lettering is pretty common on this model at this age. When I got mine, I had no choice but to replace the glass, as it had become slightly damaged in transit, as you can see.



At the time (2003) Mac no longer had the screens for the glass, and engineering had to have new ones made, or ordered. Something like that. At any rate, hopefully you won't have a problem acquiring a new glass panel.

I don't think the lettering can be repaired, once it begins to separate. I also think I see a tiny bit of delamination of the black backing just starting around the headphone jack-another common problem with models of this vintage. I think Mac has essentially addressed this issue with the replacement panels.

I also replaced the blue color meter filter with a replacement piece from Mac.

Pete

Ooouh!! That looks like an ebay job.

First off.. thanks for the kudos. At this point I really want to get it back together and crack it up, as it's been 3-1/2 weeks. Next will be the filter caps, and then the front panel glass. There's a plastic trim bezel or frame around the meters with gold accent paint on the edge. Someone apparently moved the amp with their belt buckle on and nicked it. Does the gold TRIM piece come with the glass panel?

-Gregory

[Vintage Pete]

Originally Posted by Gregory

Ooouh!! That looks like an ebay job.

First off.. thanks for the kudos. At this point I really want to get it back together and crack it up, as it's been 3-1/2 weeks. Next will be the filter caps, and then the front panel glass. There's a plastic trim bezel or frame around the meters with gold accent paint on the edge. Someone apparently moved the amp with their belt buckle on and nicked it. Does the gold TRIM piece come with the glass panel?

-Gregory

No, unfortunately, the gold-trimmed bezel bezel does not come with the replacement glass. Mac used to get these from an outside source that went out of business some time ago. So, you won't be getting them from Mac. You can check with Audio Classics for replacements; they will sometimes have them, though usually not in brand new condition. I've restored these a few times, for my vintage Mac amps and tuners. I've gotten pretty good at it.

Pete