McIntosh MA6100

[antiquekid3]

Hey guys,

I might have a chance to buy one of these power amps. However, one channel is blown. It seems to have been well taken care of over the years, though.

What would one of these be worth restored? How hard would something like this be to diagnose and repair? I've been working with electronics for at least 10 years and know a fair amount of tube and solid state stuff (though I still have a lot to learn!)

Thanks in advance!

Kyle

[Orit]

Worth repairing ? Definitely yes, as its value in working condition can be in the 500 Euros region, even if this is the most sold classic McIntosh and even if its sound is not, in my opinion, one of the best.

My father bought it in 1974, and it's still working fine without any service other than de-oxit. Very easy to service thanks to plug-in boards, the service manual is easily downloaded from the web, and it's curious to find European components inside (Philips capacitor, Austrian electros, etc).

But be very careful about the front panel: it's glass and spares are VERY costly !

[antiquekid3]

I got it! With some Klipsch Heresy speakers...all for $350! Unfortunately, the McIntosh faceplate is broken...and it definitely has some electrical problems, according to the owner. Oh, well! One Klipsch needs a new tweeter diaphragm and the other a new woofer. But I think I did pretty well for $350!

Anyone have a manual? Where could I get a new faceplate?

Thanks!

Kyle

[djk]

http://www.berners.ch/McIntosh/Downloads/MA6100_ser.zip

For glass try Audio Clasics, NY, or direct from McIntosh.

[antiquekid3]

Alright, I have located a front panel. They are so darn expensive!

I'm in the process of cleaning up and figuring out what is wrong. I've found that two of the 5A fuses are blown. I also found that both lower transistors (Q415 and Q416) are dead. The two upper transistors are just fine. I also noticed that the two left transistors have been replaced at some point because the part numbers and date codes don't match.

What do I need to replace the transistors with? Where can I find them?

Before I go powering this unit up, I'd like to know what fried the transistors to begin with. Since the two transistors that blew were attached to the positive rail voltage, I'm wondering if something happened there. But I'm not sure...

Kyle

[djk]

30 year old amplifier, you expect the parts to last forever?

Check the drivers and the bias circuit too.

Use MJ15003 for outputs, replace them all.

[antiquekid3]

No, of course I don't expect parts to last forever!! However, now that I know some of the history behind the amplifier, it does seem as though it's had a rough past. The guy who had it after his dad gave it to him used it to play (c)rap through at college. It's not a wonder some of the fuses and outputs are blown!

Can I check the driver and bias circuits without the outputs installed? Will the voltages be pretty close?

I did check the power supply by removing all of the fuses. It's right on ±46V, which is pretty close to the ±42.5V as indicated on the schematic. Is that appropriate?

Kyle

[antiquekid3]

Digi-Key - MJ15003GOS-ND (Manufacturer - MJ15003G)

Are these as good as anything?

Kyle

[djk]

Those are the ones, and a safe place to buy from.