Smoke on my power amp

@itsjustme, thanks for your comment. I would add, though, that in the specific case of tube amps having output transformers it seems pretty well established that such amps should not be operated unloaded while they are processing a signal. The concern being that "inductive kick" occurring in the transformer in that situation may damage the transformer and/or the output tubes. And I suppose the same may apply to the many McIntosh solid state amplifiers which have autoformers at their outputs.

Regards,
-- Al

To illustrate what I was referring to in my previous post, in the first of the following photos I’ve uploaded the two transistors with the grayish blobs straddling two of their leads are shown surrounded by a red rectangle. The second photo is a blowup of that area:

https://www.flickr.com/photos/32959731@N04/49419393081/in/dateposted-public/

https://www.flickr.com/photos/32959731@N04/49418924433/in/dateposted-public/

Although the limited resolution of the original supplied by the OP makes it hard to tell, I wouldn’t be surprised if those transistors were what smoked.

Regards,
-- Al

I looked at the photos pretty carefully, and the one thing I see that I’m suspicious about involves two of the output transistors in the right channel, the circuitry for which appears in the left half of the second photo.

At the extreme left of the circuit board you’ll see ten power transistors that are attached to a metal sidewall of the chassis, each of which has three leads (connections) to the circuit board. The lowermost of those transistors is near the bottom left of the photo, and the uppermost of those transistors is near the top left of the photo. Counting from the bottom up, the third and the fourth of those transistors appear to have a grayish blob straddling (and perhaps short-circuiting) the two uppermost of their three connections.

Perhaps a close-up photo of those transistors would provide further insight.

BTW, the two glass fuses in each channel (four total), which are not far from the center of the photo, are "DC rail" fuses, which should provide some degree of protection for the output transistors. But without having a schematic or otherwise being familiar with the details of the design it’s hard to say what "some degree" means.

Good luck. Regards,
-- Al

@ihcho The Google Photos links you provided in your last post don’t work, at least for members of the public. I’m not sure how or if photos uploaded to Google Photos can be shared publicly.

If you upload the photos to Google Drive, though, and then select/highlight each of them, one of the icons which will appear at the top of the listing will allow you to create a shareable link.

Regards,
-- Al