McIntosh C20 - can and should I bring it back from the dead?

[s-petersen]

You can try them,if I can find them,, they will need a little touching up, as my machinist friend imported them, and adjusted some things, before cutting them. I will look for them

Here is what I have
https://www.dropbox.com/s/3ww7m3kbiuj27s9/endcap.DXF?dl=1

 

[neevo]

Grabbed a piece of 1.2mm steel today after dropping the kids off at school. I had the dimensions of the panel but needed a way of transferring the holes. I couldn’t really mark them through the screw holes from the chassis as there wasn’t enough room, so I thought about making a paper template.

2 bits of A4 taped together as the starting point:



Taped to the chassis and I used one of the kids pencils to “brass rub” the hole pattern:



Next up I used an image of the bottom panel from clinic-audio to create the rest of the holes:



I’ve taken some artistic license here by:

1. Copying all the holes in the original panel but estimating their placement v getting it perfect as they aren’t required for mounting.
2. I’ve moved the feet holes as I don’t have the original feet. I have some of the adjustable Mcintosh feet coming from Audio Classics and drilled some 6mm mounting holes for them.
3. I made a mistake and put 3 holes just inside the sides on both sides. They should only be on the left really, so those ones I matched the diameter and left the mistake ones small.

Test fit:



Works perfectly.

Here’s the final panel with the backs of the holes tidied up:

 

[neevo]

So this means I have everything to get the chassis chromed. Annoyingly I tried to drop it off today but the chap I’ve had the quote from wasn’t at his shop. Stupid me for driving all that way and not making an appointment!

My current plan is to:

1. Get all the steel chassis parts chromed in satin chrome.
2. Send the front panel and rear panel away to be fixed up and re anodised. Clear for the back and champagne (hopefully if they can do that) for the front.

I will also be asking for some advice on the glass rails and if they can be saved or if I should look to make new ones.

In preparation for getting the parts chromed I itemised them all so I knew what I had and where it should go:



Once I have the chassis all done it leaves me I the position of being able to get the screen printing done again.

I’m in touch with someone who can do screen printing but also has a UV printing machine which uses a printer and is far more accurate. Hopefully they have a system that will work!

 

[neevo]

Like the end sequence in Kevin Costners Tin Cup I’m going over and over on this top panel. And not improving things much at all.

Here you can see some funny marks and a fair bit of dust:





Compared to the other top panel it’s not an acceptable finish:



So I’ve rubbed it back again and I have a fresh can of paint to use to stop any spatter from a half used can.

First coat on and I will let that cure before mildly rubbing it back and applying another 2 coats.

At least my makeshift spray booth is getting a workout!

 

[neevo]

Big round trip today to see the anodisers and the chromer. Unfortunately I haven’t dropped off the Alu parts yet as they need more work, but the steel parts are with the chromer for some treatment and hope to pick them up in a couple of weeks wearing their new satin chrome finish.

The anodisers were very helpful and gave me some options. They also kindly stripped all the old finish off the parts so I can get them fixed up and take them back for anodising. The finish they have when they go in is the finish they’ll have when they come out and mine need a lot of cleaning up.

I also have a dilemma! They don’t have a champagne that matches the original, it’s darker. I’m not keen to go darker and so I’m toying with the idea of going silver on the faceplate and trim. I order to see what it looked like I tried it with the stripped parts:



I think it will look fantastic and hope it’s not a terrible thing to do, but the fact I can’t get the original colour matched has me looking for solutions. It will also fit in with my Kenwood better. What do people think?

The plan is to fix and polish all the trim and have that shiny. Then brush the faceplate. I think it will look great.

I’ve stripped the frame rails of their hardware in preparation for polishing and anodising.



I’m also looking in to having the end panels made so I can polish them and anodised them at the same time to ensure the colour and finish matches. Anyone know what the original frame rails are made of? Trying to work out what grade of Alu I have the end panels made out of, 6061? 6060?

 

[s-petersen]

I would ask the finishers, I'm sure they can tell you, otherwise ask them which will finish better.

 

[neevo]

6060 finishes better but I wasn’t sure what the originals were and if I should try and match those. I’ll go for 6060.

 

[clinic-audio]

Hello Neevo

I see in your picture that you take off the insert (nut) of the top and bottom rails .....
How do you think to put them back in place ? Normally they are sealed .....

 

[neevo]

Found the picture of the champagne.



As you can see it’s pretty dark. So I think I’ve made my mind up that I’m going silver on the front instead.

So this afternoon I set about sanding out the scratches. Started with 400 grit, then 600, 800 and lastly 1200.

It’s been a long time since I cracked out the polishing gear:



I mounted the rail to some plywood so it was easier to sand:



I finished off the rail with a hard cotton wheel and some black compound. Here is a before/after comparison with the old rail:



It’s a touch before mirror finish, so I think I’ll leave it like that and hope it dulls only slightly with the anodising process. It will still be a very different finish to the front panel as that will be brushed from the start.

 

[neevo]

Hello Neevo

I see in your picture that you take off the insert (nut) of the top and bottom rails .....
How do you think to put them back in place ? Normally they are sealed .....

Correct. They can’t be put in the tank for anodising. They might press back in but I unfortunately drilled one out before I realised they were pressed in (hard). So I’m thinking I will make replacements out of Aluminium and make the fit tolerance really tight. I’m also thinking I will use some loctite on the inserts too in order to stop them moving.

Any issues with the plan you can see?

Anyone know the tread pitch of the original bolts? Worst case I can simply drill an undersized hole as they might cut their own thread in Alu.

 

[clinic-audio]

Nice result , normally once it is anodized it will look like new
The problem still exist with the insert on this rail . Aluminium would be to "soft" for kipping screws tight , steel is better but you can try with it (steel) under a big pressure to place them correctly . Don't take used ones , take brand new !

 

[neevo]

Can you buy the steel inserts?

Alternative is I make some with this...

 

[s-petersen]

I think the screws are 6-32

 

[neevo]

I can’t find any inserts cheap enough to try so will probably make some instead. That way I can control the size of the insert section to get as tight a fit as possible. This will allow me to make different sizes for the original holes and the one I stupidly drilled out.

A 6-32 tap is a much cheaper experiment than $40 of inserts that may not fit.

As a happy side note my $100 RCA jacks came in:



The pain of the cost goes away when you find out they are a direct OEM replacement, even the colour of the insulator:

 

[neevo]

I wasn’t happy with the finish on the glass rails so I cracked out the brown compound and wheel and set about fixing them up. The softer wheel and a more tentative approach seems to have paid off. It’s difficult to photograph but I have a 1 step before mirror finish on them now:





I also cracked out some sandpaper and tested some steel to see what finish I wanted on the front panel:





Looking at the panel it was in between 180 and 240.





I started with 180 but moved on to 240 in the end as it was a bit too coarse. It helped get out all the damage on the front plate though.

I built a jig to keep the panel straight as I sanded it:



All done:



I will do the rear side too just in case anything happens to the front. That way I have a backup but it will also look nicer, despite the fact it won’t be seen.

 

[nj pheonix]

I really admire the effort and detail you're putting into this project

 

[neevo]

I really admire the effort and detail you're putting into this project

It’s a beneficial mental issue

 

[nj pheonix]

I get that.
I look at many of my projects as therapy .

 

[jkaley]

Playing around in Sketchup to see if I can replicate the top/bottom and side rails. I know the pin distance on the side rails is 4.75" but does anyone have other dimensions for me? Currently I have guessed a little.

View attachment 1273622

View attachment 1273621

It would be so great to find way to be able to export these to .dxf files so I can give them to my mate to run in the CNC. Would save me a lot of money as he wouldn't have to do any computer work. Just run the tool paths. Anyone have any ideas there?

Here are some measurements. The drawing is proportional in scale, so it could be used as a template. What else do you need?

 

[neevo]

Here are some measurements. The drawing is proportional in scale, so it could be used as a template. What else do you need?
View attachment 1278918

Thanks @jkaley

You wouldn’t have the dimensions of the end plates would you? The ones with 4.75” hole spacing?