Updated with results - Need help with MC2300 - dead channel

Patrice has corrected me.
He only was Mac service for 20 years through 2000
Still in high end service.
It wasn't my intention to mislead. More to give credit where it was due:dunno:

Same here, but I was a McIntosh dealer also back in the day.

Until McIntosh changes it's dealer service requirements back to requiring Mac dealers to field service departments why would anyone want to carry those guys water just to get a discount on parts? Sorry, according to John, the last I talked to him, Patrice and I have parts crosses that he does not have.....

That said the select RCA higher voltage 3505 derivitive device, I believe back in the 90s, was Mac's output of choice. When multiple transistor suppliers were bought up by RCA the parts started testing all over the place so Mac replaced them with the Motorola MJ15003/4

I have a few NOS devices from the consolidation time and the only ones close to the original RCA devices like in the last MC2205s or the 7270s are the devices from Terry's old employer Harris.

But this is off the path, to properly repair these units you really need a scope and high wattage load resistors, and a distortion analyzer. You can screw in parts and get them to work but if you can not put them under stress, lord knows what can happen.
 
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I have been wondering about this for quite some time. I do not understand why individuals are always advocating the use of the MJ15003 type when the type originally specified (according to McIntosh service information), the 2N5303, is still readily available at a comparable price from reputable suppliers.

The MJ15003 is an excellent device,but sometimes prone to oscillation in this application. And you need a savvy tech to guard against this,as it doesn't always occur under similar operating conditions: Frequency,power level or short duration tone bursts can all trigger the oscillation. You need to be very comprehensive in your testing to be absolutely certain of stability.

I can tell you why, some of us were a bit late to the McIntosh party, its not always that straight forward finding out what the appropriate Mc/recommended part actually is.
I have used MJ15003 and MJ10524 in McInotsh amplifiers with absolutely no issue at all, I was led to believe, even by the McIntosh gurus right here in this forum, the 15003 was the recommended replacement, so that's what I have been using....never seen any oscillation on the few that I have done, and it is only a few...
Maybe its because I make sure the amps are stable......
 
Share a pic of your JBL Wall of Sound!

Well I am happy to report its back up and running great so far. Ended up that two of the outputs were bad so I replaced all the outputs on that channel with the MJ15003Gs. And like Kevin suggested I checked the emitter resistors and ended replacing both the resistors on the blown outputs with replacements I ordered from McIntosh. The other resistors were ok. I then put the new boards in from Audio Classics brought it up on a variac and DBT and luckily everything checked out. I have now run it several nights without any problems and it has honestly never sounded better. Thank everyone here so much for the all the help.

Here is the pic of it back up and running (leaving off the shelf for now just to make sure its not running hot, etc) - My JBL 100s on top of the 150as. Someday I will find either a pair of 112s or another pair of 150as. Then another 2300 and really get some wall of sound going.

H.IMG_20170820_102614.jpg
 
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