MacIntosh 2100 issues - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 18th September 2007, 06:12 AM   #1
diyAudio Member
 
Join Date: Sep 2007
Default MacIntosh 2100 issues

My MC2100 has developed a hiss on the left channel. I've also noticed that the board on the left side of the capacitors (if you consider the long branded side the front of the unit) put out far more heat than those on the right. Are these issues related? Are there any ideas of how I can fix the hissing? Thanks.
  Reply With Quote
Old 18th September 2007, 08:34 AM   #2
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
It's between 30~40 years old, it's worn out.

I would replace everything except the chassis, transformers, and heatsink.

The two driver transistors are no longer available from McIntosh, but they are still available (at a price). A set will cost about $40 for both channels. A set of 12 outputs and all the other transistors will run about the same (from an industrial distributor, not from McIntosh).

Most of the smaller caps I would buy from Digi-Key.

You may be able to find a surplus deal on the main filter caps (make sure they have fresh date codes).

I would buy the resistors from Digi-Key or Mouser.

After you freshen it up it will run another 30 years.

I might be able to arrange to have your driver boards rebuilt by a friend, I have an MC2100 to check them out in.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 19th September 2007, 03:13 AM   #3
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi djk,
Outputs worn out?

I'd be looking at caps and maybe small signal transistors first.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 19th September 2007, 03:28 AM   #4
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
"Outputs worn out?"

Maybe not, but being 30~40 years old and only about $2.50 each I would replace them while I've got it on the bench (I've seen a few in the last 10 years or so that were blown).

Drivers are RCA 40409/10.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 19th September 2007, 04:44 PM   #5
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi djk,
My cost is a fair bit higher per piece. Then there is the labour of picking out matched sets along with the "waste" of transistors that do not match.

If we are going to do this, may as well do it right. I must say that On Semi's newer parts have a much higher yield though.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 20th September 2007, 12:01 PM   #6
diyAudio Member
 
Join Date: Nov 2002
Chris,

Even with the higher cost associated with replacing the outputs and drivers the end result is well worth it. Outputs never go to waste because they can sit on the shelf until they are used and the cost is naturally passed on to the consumer. I learned the hard way that DJK is correct. Years ago I was trying to repair a large power amplifier and I got it running but failed to listen to Mr. DJK's warnings to replace the driver and output stage and blew it up again. I repaired it the second time and replaced all the semiconductors per DJK's recommenfations and it is still running to this day and that was over 25 years ago.

Years ago Mr. DJK was the service manager of a large high end electronic store that was a major MacIntosh dealer and he knows his ****.

Quote:
Drivers are RCA 40409/10.
Are the RCA parts still available today or were these house part numbers? What can they be replaced with ?
  Reply With Quote
Old 20th September 2007, 01:16 PM   #7
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Digi-Key current cost for TO-3 devices is $2.45 each in 100 lot trays (most models). Probably higher in Canada.

The RCA 40409/10 are the original RCA part numbers and used in other designs (all the SWTPC amps). I buy mine from a distributor:

http://www.magicparts.com/

In Canada:

http://www.audionova.ca/


This list is for the MC2100, electrically it is the same as the MC2105, just without the meters.

Even though your old amp is still working, you have no idea how much of the music you are missing.

The parts are inexpensive.

Digi-Key is good, Mouser has no minimum order.

Posted by djk (M) on July 11, 2004 at 04:29:36
In Reply to: Re: MC2105 @ $ 100 even @ 20 yrs old is a best buy for me. posted by julian4@telkomsa.net on July 06, 2004 at 14:58:04:


The sound would benefit greatly from replacing a few dried out electrolytics, and adding a few film types here and there.
C301, 302 is the main input coupling cap. It is a Mylar type so it is likely to be OK, upgrading it to a Polypropylene type with give a smoother sound to the high end (0.47F).

C307, 308 are emitter bypass caps, 100F 15V. Replace with same type and add a 0.1F film bypass.

C309, 310 are the output coupling caps for the pre-driver section, 10F 25V. While a film type would be better, size is a problem. The DC bias across this cap also helps out with its being an electrolytic. Replace with same type and add a 0.1F film bypass.

C303, 304 are the DC power supply caps for the front end, 470F at 25V. Replace with same type and add a 0.1F film bypass.

C1, 2 are the feedback loop caps, 330F at 3V. The signal goes through these so replacing these with new ones and adding a 0.1F film bypass really opens up the sound. Go with as high a voltage as what space permits.

C11, 12 are the DC supply caps for the voltage gain stage, 150F at 50V. Replace with same type and add a 0.1F film bypass.

C201, 202 are the main filter caps, 39,000F at 40V. These may be quite expensive new, although I have seen them surplus for very low prices. I would use then unless signs of leakage or amplifier hum are there. Add a 47F at 50V cap in parallel with each.

C203 is a multi-section cap that will be very hard to find a fresh date code. New caps are small enough that they may be wired to the terminals of the old one, leaving the old one in place. This cap is important as it provides the current for the diff pairs and the VAS. The sections go 80/80/150/50F with the voltages being 200/200/150/150V. If you measure the voltages 100/95/90/80V are typical, so 200V caps are not really needed, but 100V is not enough.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 20th September 2007, 05:20 PM   #8
pchw is offline pchw  United States
diyAudio Member
 
Join Date: Apr 2006
Location: Fremont, California
First, I apologize for the thread jack. While we are discussing Mac's,
I would like to seek some advise.

I have a MC2120. I believe it is very close to the MC2100, no meter
and 20 wpc more. It has a problem that the right channel produces no sound when power on, sometimes it comes back after a few mad on/off's. Then it will stay until the next power on/off. I sent this to a Mac authorized repair shop, and the problem came back after 90 days warranty expired and $450 lighter ..... So, I am going to try repairing it myself. Any advise where the problem might be? I do have the service manual.

Thanks,
__________________
- Fred -
  Reply With Quote
Old 20th September 2007, 05:52 PM   #9
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Fred,
I have seen some intermittent relay contacts and the odd bad solder. I've even had an intermittent capacitor kill the sound.

Hi Joe,
Just questioning to pick up some knowledge here. I will replace outputs when I see issues. Low gain is the most common, followed by leakage. I suspect in your case that you may have had some leaky transistors. Just guessing since I have not seen the amp and only you can know exactly what happened. After it blowing up again, I would have done the same thing. I do tend to measure gain and leakage in my normal cleanup.

Hi djk,
Quote:
Probably higher in Canada.
For sure!
You are giving good advice for someone who doesn't test the output transistors. I normally test them all and rearrange them if needed to match gains between channels and push or pull ( ). I haven't had one come back yet, although a couple didn't pass the hot test. Never for a blow up though, always an intermittent.

Please don't take this as a criticism at all. I'm here to learn also.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 20th September 2007, 06:17 PM   #10
diyAudio Member
 
Join Date: Nov 2002
Chris,

I do own 3 Sencore transistor testers and I do always test the transistors. I do find however that age is an important fact here as I have had problems with transistors that showed no leakage and had gain within the normal parameters.

I still change out the old transistors with new matched ones because it makes life so much simpler in the long run.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
orion 2250,2100,Concept 97 modd issues amc32 Car Audio 1 12th August 2008 08:04 PM
Recovering old Macintosh HFS HDs on a PC ? Pjotr Everything Else 4 19th August 2007 05:53 PM
Ripping DVD-A on Macintosh serengetiplains Digital Source 0 14th January 2006 11:55 PM
Macintosh Digital Out serengetiplains Digital Source 0 9th December 2005 09:59 PM
XP scrapbook, clipbook like Macintosh peranders The Lounge 4 13th August 2003 11:26 AM


New To Site? Need Help?

All times are GMT. The time now is 10:34 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2