Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Repairing an old McIntosh
Repairing an old McIntosh
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
Thread Tools Search this Thread
Old 10th November 2000, 10:25 AM   #1
namui is offline namui
diyAudio Member
Join Date: Nov 2000
I'm repairing my 20+ year old McIntosh MC2125 poweramp.
I got the service manual already, so I have all the circuit details.
The problem with my amp is - occasionally, the left channel would gradually fade and starts to sound sniffy.
Many time, the sound will finally be gone. Lately, the right channel starts to have similar problem, but a lot less serious. The power guard light also turned red quite often.
The problem is I don't know where to start checking because it doesn't always happen. If I leave the amp off for a few days, it will normally come back to work properly for half and hour or more. Any suggestion ? I plan to have it overhauled anyway. But which parts of the circuits are most likely need to be replaced ? Thanks
  Reply With Quote
Old 10th November 2000, 10:13 PM   #2
pixie is offline pixie
diyAudio Member
Join Date: Oct 2000
Location: Austin, Texas, USA
Default Testing.

This sounds like a thermo-shutdown problem. So, one of the tubes or transistors is overheating (whichever this amp is?)

Try a can of Freon(sp?). Keep one component cold until the amplifier shuts down. Then you know it's Probably not that one. It's a slow process, but it will isolate the problem IF it is indeed a overheating problem.

Of course there's always the old standby... Ow! Yep it's that one!

  Reply With Quote
Old 2nd January 2001, 04:15 AM   #3
robertpear is offline robertpear
diyAudio Member
Join Date: Jan 2001
Location: Lawrence, Kansas
This sounds like you have one or more leaky output transistors. Rebulid the amp with new quality outputs (Motorola is my favorite). Also the power supply filter caps are proably week and need replaceing.
Bob P
  Reply With Quote
Old 4th May 2005, 01:35 PM   #4
audiofan is offline audiofan  Canada
diyAudio Member
Join Date: May 2003
Location: quebec
few questions?

Is that amp solid state ?

Is the power suppy regulated type ?

Is there current limiting in power supply ?

If yes to all find shunt resistor in current limiting circuit and the transistor used with it.

If the transistor is normally at cutoff with a high voltage ( emitter- collector ) across , it could produce your trouble.
  Reply With Quote


Repairing an old McIntoshHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mcintosh C28 Karrry Solid State 1 28th April 2009 04:06 PM
SE amp like mcintosh ? jeapel Tubes / Valves 20 29th March 2005 02:47 PM
Repairing Mcintosh MC2300 diyman Solid State 0 12th August 2004 12:13 PM
Mcintosh C26 bonsai171 Solid State 2 8th May 2004 03:58 PM
Repairing an old McIntosh : Part II namui Solid State 2 5th February 2001 01:16 PM

New To Site? Need Help?

All times are GMT. The time now is 09:06 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio