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McIntosh (MC601) amplifier overheating problem

Hello everyone - A buddy of mine has MC601s that have recently started overheating.  Each amp went into protection mode after emitting a burning smell, and both had to have an output transistor replaced (at different times).  

My internet digging has revealed that ThermalTrak transistors are not very reliable, or at least the early batches were not.  Ayre has also reported overheated MX-R amps with the same problem.  They apparently can fail after years of use, which is not good news for owners!

I'm trying to get a feel for how widespread this problem may be (at this point in time)?  Each transistor replacement is $400, and there's an awful lot of output transistors in MC601s...!!  I convinced my brother to also get MC601s so I'm starting to get really worried his will fail too in the near future.

So far, McIntosh's response to my inquiry has been vague and reticent, unlike Ayre who apparently went to great lengths to remedy this issue for their owners.  Has anyone out there had this problem with McIntosh or Ayre?  

aball
aball OP
2,016 posts
 
Hi garebear, nice to hear from you!

Hi chazzzy, ok well wish him good luck. It has now been 55 days and still no parts, and no emails in the last 2 weeks. To add insult to injury, I got an automatic reply from the Customer Service Manager just now saying that he’s out of the office until 8/10. Well, today is 8/22.... Unfortunately, I think that says it all.
pbnaudio's avatar
pbnaudio
1,610 posts
 
Just thinking out of the bag here - if the choice of output transistor is questionable - and from what I read in this thread this is likely the case - is there a substitute available which does not suffer from this ailment? There is literally 100s of BJT,s designed for AF.

Best of Luck

Peter 
pbnaudio's avatar
pbnaudio
1,610 posts
 
http://www.onsemi.com/pub/Collateral/NJL3281D-D.PDF

May not be that easy 😄

Best of Luck

Peter 
pops
2,272 posts
 
Arthur, thanks for the update, however not the good news I was hoping for being a Mac owner.   Best of luck and kick their a$$!
aball OP
2,016 posts
 
Ok!  McIntosh finally came through.  Unfortunately, they did not want to swap the amps out for us (as Ayre has done for the exact same problem and situation), but they did send us 4 complete heatsink assemblies that are fully-populated and tested, ready to be installed in both monoblocks.  I have performed the swap for the latest faulty amplifier, and it wasn't very difficult, although it does require the amplifier to be on its side, which is a dicey proposition.  

We feel this is a satisfactory solution.  It took 120 days all said and done to get the parts.  Not impressed.  Good thing we have spare amplifiers laying around.  But, we are very happy they helped us out!

Now, fingers crossed that my brother's MC601s don't overheat...or anyone else's for that matter.
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