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

Yeah I know it’s a preamp... just can’t be arsed to write preamp each time. Might go with Pre instead :)

Interesting question from that though. I assume you don’t have to connect something to a preamp when you’re firing it up like you would with a tube amp?

Ok then, very well, was just wondering. :confused:

Nothing needs to be connected to the pre-amp`s output, whether tube, or SS, even with something driving it`s input.

It won`t get upset driving "Air"(zero load/infinite impedance), just won`t perform any useful musical listening function whilst doing so. :bigok:
That rough and abused C20 is certainly going to be a project. :eek:
 
@s-petersen can you tell me more about the parts you made? Specifically the side plate and glass end plates. Wondering if I can make replacements for the top, bottom and sides as I don’t have the sides and the top/bottom have some gauges.
 
I have a plan of attack. I’m on the hunt for parts. Tried to contact McIntosh direct in the US but they passed me on to the AUS refurb centre instead. Asked them to see if Mac has a faceplate and I’ll be interested to see how much it is if they do as markups are huge in Oz.

Next up I’ve decided I’m going to fix the chassis. I know I agreed to fixing up the electronics first but given I’d need to strip out new parts again to fix up the chassis, that doesn’t make sense. I’d prefer to put the electronics (new and old) back in to a chassis I’d be proud of. Especially considering the cap kit for the filter caps is $300!
 
neevo, don't get discouraged. Like the man who ate a bicycle once said when asked how he did it...."One bite at a time."

Those who read Guinness Book of World Records for fun might know the Frenchman I speak of.
 
Question for those that know this sort of stuff. I’m looking to replicate the original finish on the chassis. Thinking about having the chassis electroplated. Anyone think of a plating that would best match the original?

I was thinking either zinc, tin or nickel.

I’m not after shiny so chrome seems out.
 
Chrome plated is original finish, nickel maybe as alternative. Hammertone gray for painted.
 
Gosh it is almost 40 years ago now but I do remember sitting in Gordon Gow's office while he explained to the facts of McIntosh life but in the US and what he expected for the baryons export markets.

It was months later during dinner when he expounded on the barriers both cultural and financial that so many countries put on US imports and the reasons why he signed exclusive agreements with local importers to deal with those barriers. Many of those now decades old agreements are still active and McIntosh honors them. (old issues are now everyday news).

As Patrice has pointed out their are worldwide specialists who can custom supply the various pieces you will need......they do these services not as a hobby though but they do step up to supply resources for these 60 year old classics.
 
After plating, or painting, it also needs silk screening as well. keep in mind you can pick these up for less than 2k in decent cosmetic condition, and if you go crazy, it would not be worth it. Remember the chassis can be hidden in a cabinet, the face is all you see.
 
It's a little shocking to see a once beautiful preamp in that sad condition . I applaud you for trying to resurrect it. I will be following your progress.
 
After plating, or painting, it also needs silk screening as well. keep in mind you can pick these up for less than 2k in decent cosmetic condition, and if you go crazy, it would not be worth it. Remember the chassis can be hidden in a cabinet, the face is all you see.

That’s correct. I’ve actually been reading up on how to silkscreen to see if I can do it myself. I’d be comfortable with the tube details on the top cover but the back panel might be a bit too much to create, hence why I was thinking I’d leave the back panel alone. It could be a reminder of the original state of the preamp.
 
Fair bit done tonight to get the preamp ready for a bath, before final stripping so I can get the chassis stripped and treated.

I’ve taken loads of pics to serve as a reminder, plus I’ve labeled wires with tape of done the obligatory sandwich bags with parts and labels.

First job was putting all the knobs etc in some soapy water for a couple of days before i Given them a scrub with the wife’s toothbrush ;)

F859F4ED-CC56-4910-AF07-F5AD16733699.jpeg

The next big job was to desolder the transformer. I carefully labeled all the wires so I know where it goes back:

197ED3C8-FE0E-4FD0-B6BE-94094F5B453C.jpeg

I need some advice here:

1. I was going to strip the old paint with chemical stripper. What do people think?
2. The wires are very stiff and the coverings are brittle and cracked. Any advice on what to do here? Leave as is? Replace them by joining new ones at the transformer? Strip the fabric outer sheath and replace just that?
 
KNext up I set about stripping parts off. First to come off was the power cord. Only because it is much easier moving the preamp around the bench without it. It attaches to either side of the rear non switched socket:

7092BE7D-82AD-469E-B7BF-05EBFC35E4E3.jpeg

Then I stripped the hardware from the front of the preamp:

B1B513CF-8FAA-4BA7-A0CE-E653869C4B91.jpeg
E4BFB331-530F-4F72-9C2C-B518A3FE21FB.jpeg
27209A74-A1FF-410A-B7AA-4EF35397AECD.jpeg

I have a mystery here... a wire with no home:

65714ED4-D346-4C06-BFDA-2963412CCEA7.jpeg

Green. The black and green/white ones have a home. I thought it might go to the right 1/4” jack as that one only has 1 wire, but there’s nothing broken on that so maybe that sockets does only have 1 wire:

5727CEDE-F342-4C31-9F40-273FB375BB88.jpeg

Either way it all came off, including the sockets:

CBD0D52B-F09A-493B-9C50-E2BA01B00F6D.jpeg
 

Attachments

  • 18C8BD75-27C7-4F77-97CB-4141AC76273D.jpeg
    18C8BD75-27C7-4F77-97CB-4141AC76273D.jpeg
    105.4 KB · Views: 10
So that’s where I’m up to so far:

EB44D094-ECE3-4B00-8690-42000CD533EA.jpeg

0FA83164-D8F0-4535-86D5-281566ABE61B.jpeg

2C192AD7-0346-4BD8-8872-615936D4E88A.jpeg

Now I’m keen to give the boards and leads a bath before I strip the chassis. I noticed someone gave their Marantz 8 a complete bath and I’m inclined bed to do the same, or maybe a wash in the dishwasher. What do people think?
 
Back
Top Bottom