Bob the Tech Audio repairs fine Audio / Video equipment such as this McIntosh Laboratories MX121 with intermittent audio output. I just finished checking out the repair on this MX121 home theater processor. I isolated the issue to a poorly installed connector, as seen in the picture. The result was a bad connection between audio board and the back panel. This resulted in intermittent loss of control of what was happening on the audio board and no output. If your McIntosh Laboratories MX121 has intermittent audio output, or for any other fine A/V service needs, contact Bob the Tech Audio.
No, I didn’t leave it there, I dusted it off before reinstalling covers 
Checking out the HDMI A/V inputs
