Sick McIntosh MC2300, No Left Channel

[swantzilla]

The output from my Mc2300 left channel is missing. However the meters show that there is output which is concerning. I did a resistance check on the output of the autoformer and see very low resistance on the output side and is comparable to the working side. There is also continuity to ground. I have not removed the amp from the audio cabinet yet as it is a monumental task so I am just wanting to get some ideas beforehand.

The amp has been re-capped (except for that multi-section cap) and matched transistors installed. The fact that the meters show output makes it look like the autoformer or the connection in to the autoformer. I guess I always assume the worse.

Thank you for reading.

 

[llwhtt]

The meter is driven right from the amplifier circuitry so you are good there. Any chance the speaker got disconnected at either end? Pets chewing on speaker wires? I can't imagine an autoformer going bad, but anything is possible.

Craig

 

[swantzilla]

Thanks for the reply. The speaker wires are good as I verified it by hooking both the right and left channel speakers together on the working right channel. Resistance measurement comparing the values at the right and left speaker terminals are the same.

 

[djk]

The meters hook up to the input to the autoformer.

http://www.hifiengine.com/manual_library/mcintosh/mc2300.shtml

You need to check the continuity of the autoformer.

 

[swantzilla]

Finally got the amp out of the cabinet. I found the wire in the connector that goes from the left channel autoformer to the lug on the PCB where the large caps are burned and disconnected. It was burned at the connector end so I was able to cut about 2 inches off the wire and found good copper. I spliced in a suitable wire and put on a new spade connector. Before I put things back together I wanted to compare the resistance with the good channel. I put some pressure on the other channels autoformer wire and it slid right out of it's connector. The wire was in good shape so I just put a new spade connector on it. I also found another spade connector that one of the compression sides broken off so I had to replace it. So I may have dodged an autoformer bullet. I will try to put it back together tomorrow. I am considering replacing all the high current spade connectors. Then it can be back to it's job of producing signals from 80hz on down. Thanks for reading. Whew.

 

[djk]

I have cut off the Fastons and soldered directly on other McIntosh models, the input connectors to the autoformer carries over 30A on peaks.