Don’t buy used McCormack DNA 1990s amps

@nymarty Sorry to undermine the potential sale of your amp and glad your is still working!  And yes, I’ll let you know my thoughts on the amp once I get some hours on her.  
As promised, here’s the reply from SMcAudio on the input board issue…

The through-hole plating issue is a global issue with the driver pcbs for DNA-1, DNA-0.5, HT-1, HT-3, DNA-2 and ALD-1.  It affects the power supply, driver stages and protection circuit on the PCB.

  It is a real problem that caused us and our customers lots of grief as odd failures were repaired only to have a different odd failure crop up weeks or months later. Attempting to repair these boards reliably becomes an expensive game of Wack-A-Mole and often results in solder doing the job of carrying power and signal instead of copper which sounds bad and isn’t reliable.

 The issue does not affect the output PCBs of these listed amps nor do they affect the Virginia Series amplifiers such as the DNA-125, and DNA-225 because these amps only have plating on one side of the PCB (so through-hole plating issues will never be a problem)

 We made the decision in late 2014 to no longer work on these boards and made a replacement PCB that eliminates the potential of plating issues (better PCB material, much heavier plating and redundant vias where necessary)

These PCBs are superior in everyway and have proven to be exceptionally reliable and they incorporate the 20 years of mods and revisions that SMc Audio has developed however the replacement PCB is not a drop-in replacement and requires additional work on the amplifier.

 Hope this helps.  People can always give us a call if they’d like to.

@kchamber 

Thanks for the great post. Please stick around for more on this thread or others. Do you still perform repairs for others? Mind telling us a little more about your background and where you are located?

However, I’d be willing to bet that 50% or more of them will still be kicking with their original input boards 10 years from now.

@kchamber You’d be willing to bet based on what? Faith? Other people’s money? Where does 50% even come from? Outta your butt? You’re willing to “bet” means precisely ZERO to someone buying one of these amps. And by the way, who wants to buy an amp with a 50% failure rate even if you’re right, which you probably are not. The design is prone to failure, especially after 20+ years for the reasons stated by the guys who built the amps, which is not you. Period.

@soix 

Convinced of your belief, you are being harsh and extreme, IME. You also have no basis to claim the converse-that every 1990's McCormack amp has either failed or is on the verge of failing. IMO, kchamber's viewpoint is likely more realistic. I can not think of too many consumer products that have had a 100% failure rate, not even the dreaded Yugo. 

@soix 

You're correct I pulled that number out of my butt, using nothing but my 35yrs of experience designing and working on electronics in semiconductor manufacturing and research.

Guess what? Krell & Levinson amps of the same vintage are also very failure prone. In fact, probably more so for some models due to heat stress. The people buying those 30yr old amps for kilobucks do not seem to care? Does that make you angry too?

Anyone that is really concerned about one of these DNA amps failing should invest in having a true DC protection circuit installed by a competent tech. That includes the new input boards that SMc is selling because they do not have true DC output protection either. The DC protection in the older DNA amps is only an input muting circuit.