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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Tue 03, 2012 4:46 am 
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OMG why did I decide to recap this thing. This guy is a PITA to recap. Like 6 hours later, I only have the can caps in, and one board done. There is like no room for your fingers in this thing, and no room to snip off the old caps. Forget desoldering everything from the lugs, I would destroy the carbon resistors in the process. Ugh, I will work on it some more tomorrow. Still have to test all the tubes, and maybe refinish the cabinet.

Can anyone help me out with the diodes? I want to replace them why I am in there, but there is no voltage reading. The parts list just says 1.1A. I seen on ebay that a rebulider uses 3a 1000v diodes...I couldn't find any of them at the rat shack...wondering if I can use something lower or should I order them.

Oh and I have noticed a number of the BB's are cracked :shock:


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Tue 03, 2012 6:09 am 
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Cracked Bumblebees, eh?

Sell 'em to some fool, and say they're broken in. :shock:

Wanna do a re-cap of a Pioneer SX-1250?

LOL!

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Tue 03, 2012 6:19 am 
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RepairTech wrote:
Cracked Bumblebees, eh?

Sell 'em to some fool, and say they're broken in. :shock:

Wanna do a re-cap of a Pioneer SX-1250?

LOL!


Hey I just may list them for the fun of it

I am okay with that, thats why I never keep in of the high end silver face guys I get....I get scared just looking in them..


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 6:45 am 
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Well its done...PITA...but its done.

I don't know whats going but I'm getting 500v off the rect when I should be getting 330v...and my tester decided it didn't want to test the 12AX7's...but it is playing fine and sounds pretty darn good.

Image


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 2:58 pm 
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BigBandsMan wrote:

Guitarists, few of which have any technical literacy worth mentioning, soon discovered this. Some relatively bright spark among them decided that the "bumblebees" were being kept for their "sound" and started the word around. Now it has the force of Holy Writ among the twangers and bangers.

Larry


This cracked me up big time! :lol:

You pretty much nailed it (and I'm a guitarist).

Nice work Cooljjay!


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 4:48 pm 
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Rumble wrote:
BigBandsMan wrote:

Guitarists, few of which have any technical literacy worth mentioning, soon discovered this. Some relatively bright spark among them decided that the "bumblebees" were being kept for their "sound" and started the word around. Now it has the force of Holy Writ among the twangers and bangers.

Larry


This cracked me up big time! :lol:

You pretty much nailed it (and I'm a guitarist).

Nice work Cooljjay!


What really "cracks me up" is the plethora of websites and discussion blogs concerning guitar amp "mods" and tube rolling, among tons of DIY schematics.

If these bumblebees are so worshipped for their original sound, how come they've got to modify the amps, mess with the bias, and redesign "tone stacks"?
It would seem kind of contradictory to change original designs to suit, yet praise junk parts.

But then again, I've never met a musician who wasn't somehow "off" in their way of thinking, anyway. :roll:

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 4:56 pm 
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RepairTech wrote:
But then again, I've never met a musician who wasn't somehow "off" in their way of thinking, anyway. :roll:

I guess I'd better not mention that at my advanced age I'm studying piano, and my wife is studying violin!

-David


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 7:35 pm 
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dberman51 wrote:
RepairTech wrote:
But then again, I've never met a musician who wasn't somehow "off" in their way of thinking, anyway. :roll:

I guess I'd better not mention that at my advanced age I'm studying piano, and my wife is studying violin!

-David


No no, wait for it. They're going to say guitar isn't a "real instrument". :D


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 8:02 pm 
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928GTS wrote:
dberman51 wrote:
RepairTech wrote:
But then again, I've never met a musician who wasn't somehow "off" in their way of thinking, anyway. :roll:

I guess I'd better not mention that at my advanced age I'm studying piano, and my wife is studying violin!

-David


No no, wait for it. They're going to say guitar isn't a "real instrument". :D


Of course it's a real instrument. The problem is finding someone who treats it that way.
If they'd simply quit trying to make noise with it and actually explore its potential, it is capable of at least as much expression as an acoustic (i.e. classical) guitar.

By the way, you aren't likely to find many real musicians at the techno-illiteracy havens described by RT above. The usual specimens who infest those websites haven't yet learned that music involves rather more than noise strewn along a timebase. Worse yet, they have no intention of learning.

Their philosophical ancestor, having finally got his guitar in tune, proceeded to weld the machines...

Keyboards since 1968 and COUNTING :mrgreen:

Larry

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 8:11 pm 
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BigBandsMan wrote:

Of course it's a real instrument. The problem is finding someone who treats it that way.
If they'd simply quit trying to make noise with it and actually explore its potential, it is capable of at least as much expression as an acoustic (i.e. classical) guitar.

By the way, you aren't likely to find many real musicians at the techno-illiteracy havens described by RT above. The usual specimens who infest those websites haven't yet learned that music involves rather more than noise strewn along a timebase. Worse yet, they have no intention of learning.

Their philosophical ancestor, having finally got his guitar in tune, proceeded to weld the machines...

Keyboards since 1968 and COUNTING :mrgreen:

Larry


What you may think of as noise may be regarded by others as a beautiful orchestra of harmonic content. That's what makes human nature great. Due to our unique nature many different views are held about a single item. There's little benefit in trying to be critical or debasing about one's view. Instead, be accepting and respectful of one's views or opinions even if you may not agree with them.


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Wed 04, 2012 8:12 pm 
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928GTS wrote:
BigBandsMan wrote:

Of course it's a real instrument. The problem is finding someone who treats it that way.
If they'd simply quit trying to make noise with it and actually explore its potential, it is capable of at least as much expression as an acoustic (i.e. classical) guitar.

By the way, you aren't likely to find many real musicians at the techno-illiteracy havens described by RT above. The usual specimens who infest those websites haven't yet learned that music involves rather more than noise strewn along a timebase. Worse yet, they have no intention of learning.

Their philosophical ancestor, having finally got his guitar in tune, proceeded to weld the machines...

Keyboards since 1968 and COUNTING :mrgreen:

Larry


What you may think of as noise may be regarded by others as a beautiful orchestra of harmonic content. That's what makes human nature great. Due to our unique nature many different views are held about a single item. There's little benefit in trying to be critical or debasing about one's view. Instead, be accepting and respectful of one's views or opinions even if you may not agree with them.


:roll:

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Thu 05, 2012 1:29 am 
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dberman51 wrote:
RepairTech wrote:
But then again, I've never met a musician who wasn't somehow "off" in their way of thinking, anyway. :roll:

I guess I'd better not mention that at my advanced age I'm studying piano, and my wife is studying violin!

-David



I knew something was "funny" about you... :shock:

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Sat 07, 2012 1:52 am 
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My dear C-20 remains all original, except for a can I replaced about 30 years ago. I thought about re-capping the thing, but will wait for a problem to show up. It sounds absolutely great to my ears, so if it ain't broke, I ain't gonna "fix" it. :D

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Sat 07, 2012 2:24 am 
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stromberg6 wrote:
My dear C-20 remains all original, except for a can I replaced about 30 years ago. I thought about re-capping the thing, but will wait for a problem to show up. It sounds absolutely great to my ears, so if it ain't broke, I ain't gonna "fix" it. :D


I would go in and check the voltages if anything. After the recap, I noticed 25% of the BB caps were cracked open. So yes it works but how much damage you can do with it running with old caps is a question for the universe.


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Sun 08, 2012 6:58 am 
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cooljjay wrote:
stromberg6 wrote:
My dear C-20 remains all original, except for a can I replaced about 30 years ago. I thought about re-capping the thing, but will wait for a problem to show up. It sounds absolutely great to my ears, so if it ain't broke, I ain't gonna "fix" it. :D


I would go in and check the voltages if anything. After the recap, I noticed 25% of the BB caps were cracked open. So yes it works but how much damage you can do with it running with old caps is a question for the universe.


25% cracked, 75% failed in some way that happens to be less obvious. Just say NO to bumblebee caps!

Brett


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Apr Sun 08, 2012 4:37 pm 
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It's really simple.

When running such equipment with AGED capacitors, it causes stresses.
Leaky caps allow DC into the grids of output tubes.
This now causes the tube to run HOT, drawing more current.
This increase in current helps to elevate output transformer temps.
Eventually the tube fails - taking out anything in the B+ line.


Old power supply 'lytics load down the rectifier, in turn loading down the power transformer - eventually cooking it.
Bias supplies with aged caps and selenium rectifiers also tend to fail, causing output tube failure due to elevated currents.

With this knowledge, why would ANYone continue to use equipment with a ticking time bomb in it?

Makes no sense, unless you like spending lots of money on expensive transformers due to negligence. :roll:

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Feb Sat 08, 2014 9:20 pm 
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Location: Van Buren, Arkansas
Ha ha. I have re-cap'd and replaced all the resistors in 3 (yes three!) C-20's. It is a time-consuming process, but the results are quite worth it. Don't forget to replace the selenium rectifier under chassis which is used for the DC supply for the tube filaments.


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Feb Mon 10, 2014 11:31 pm 
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I generally agree with the "re-cap all" in vintage gear, the old caps, including BB's will, or are bad and can cause significant damage when voltage is applied to the whole unit. That being said, particularly on expensive vintage gear, keeping the original parts will result in a MUCH higher resale value. Not my place to tell someone how to spend their money, but the facts are the facts! I have a stash of vintage BB's for those high-end units if I need to replace any bad BB's, all my replacements are checked out on my Sencore LC 53 at full voltage before installation, and then the circuit is monitored afterwards. Personally, I would have left it alone and re-sold it at the stupid prices many are willing to pay, and use the money to by a MUCH better preamp, modern preamps are really much better, better topology, parts, but that is just me. I am in it for the great sound a great system can have, and much of that sound is not in vintage gear, although, as always, there are exceptions...


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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Feb Tue 11, 2014 12:53 am 
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Randy Warren wrote:
I generally agree with the "re-cap all" in vintage gear, the old caps, including BB's will, or are bad and can cause significant damage when voltage is applied to the whole unit. That being said, particularly on expensive vintage gear, keeping the original parts will result in a MUCH higher resale value. Not my place to tell someone how to spend their money, but the facts are the facts! I have a stash of vintage BB's for those high-end units if I need to replace any bad BB's, all my replacements are checked out on my Sencore LC 53 at full voltage before installation, and then the circuit is monitored afterwards. Personally, I would have left it alone and re-sold it at the stupid prices many are willing to pay, and use the money to by a MUCH better preamp, modern preamps are really much better, better topology, parts, but that is just me. I am in it for the great sound a great system can have, and much of that sound is not in vintage gear, although, as always, there are exceptions...


A very sensible post. I'm all about the sound too, and have long since given up on the nostalgia aspect. As revered as the old Mac pieces are, they are really rather crude from a performance standpoint by today's standards, compared with even modest modern equipment. Beyond the bumble bee caps, you'll find a large number of carbon composition resistors at 10% tolerance or worse, dual gang volume controls with channel balance no better than a couple dB, especially at the low end of the range, and very basic unregulated power supplies. Not a cut against McIntosh, more just a reflection of what was possible at the time it was made. They can still sound good, but give up a lot in noise level and overall transparency.
Just as an example, a friend just purchased an NAD preamp on sale for about $600, that is really nicely built, has a super quiet phono stage, a stepped attenuator volume control with remote and uses top quality glass epoxy circuit boards with 1% metal film resistors and polypropylene caps. It uses a toroidal power transformer and a fully regulated power supply. Switching is all done using hermetically sealed relays operated by a microprocessor. It also sounds completely transparent to my ears when using the line stage. I haven't tried the phono section yet. Very hard to beat, especially at the price.

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 Post subject: Re: Mcintosh C20 Recap....
PostPosted: Feb Tue 11, 2014 2:11 am 
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Posts: 573
Location: Fairfax, VA
jmsent wrote:
Randy Warren wrote:
I generally agree with the "re-cap all" in vintage gear, the old caps, including BB's will, or are bad and can cause significant damage when voltage is applied to the whole unit. That being said, particularly on expensive vintage gear, keeping the original parts will result in a MUCH higher resale value. Not my place to tell someone how to spend their money, but the facts are the facts! I have a stash of vintage BB's for those high-end units if I need to replace any bad BB's, all my replacements are checked out on my Sencore LC 53 at full voltage before installation, and then the circuit is monitored afterwards. Personally, I would have left it alone and re-sold it at the stupid prices many are willing to pay, and use the money to by a MUCH better preamp, modern preamps are really much better, better topology, parts, but that is just me. I am in it for the great sound a great system can have, and much of that sound is not in vintage gear, although, as always, there are exceptions...


A very sensible post. I'm all about the sound too, and have long since given up on the nostalgia aspect. As revered as the old Mac pieces are, they are really rather crude from a performance standpoint by today's standards, compared with even modest modern equipment. Beyond the bumble bee caps, you'll find a large number of carbon composition resistors at 10% tolerance or worse, dual gang volume controls with channel balance no better than a couple dB, especially at the low end of the range, and very basic unregulated power supplies. Not a cut against McIntosh, more just a reflection of what was possible at the time it was made. They can still sound good, but give up a lot in noise level and overall transparency.
Just as an example, a friend just purchased an NAD preamp on sale for about $600, that is really nicely built, has a super quiet phono stage, a stepped attenuator volume control with remote and uses top quality glass epoxy circuit boards with 1% metal film resistors and polypropylene caps. It uses a toroidal power transformer and a fully regulated power supply. Switching is all done using hermetically sealed relays operated by a microprocessor. It also sounds completely transparent to my ears when using the line stage. I haven't tried the phono section yet. Very hard to beat, especially at the price.


+1 on that! One of the things I have learned most recently about really good gear is how QUIET they are. Those things in audio that distingush the great from the good usually have very low noise; very low hum, tube rush, mechanical buzzing, etc. I don't know if that was something that was considered in vintage gear, it certainly was a MAJOR consideration for the gear used to make the recordings, and now in the high-end audio, all noise is eliminated as much as possible. The main difference in sound quality is the ability of the audio gear to reproduce the quietest parts of the music, these micro sounds are all too often covered by noise, when they are allowed to be heard, the sound difference is quite amazing, reflections of the hall, sounds of air moving, etc., this is what we so often hear in live music that is missing in reproduced music...


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