This was a quick one so no pics, sorry. The HS80M is an active 2-way studio monitor with bass-reflex design, 8" woofer and 1" tweeter.
Design: Each monitor is stand-alone, active bi-amplified. It accepts 1/4" TRS jack or XLR inputs. It has a regular mains transformer power supply, 2x LM3886TF for power amps and NJM4558 opamps in the signal section.
Fault behavior: The affected monitor didn't light up the Yamaha logo on the front and did not produce any sound.
Diagnosis: Mains fuse fine, main power rails fine, no DC offset at the output of the power amps, speakers fine. So it had to be something in the signal path.
Fault: Missing +15v rail for the signal section.
Culprit: KIA7815 regulator on the main board, also obvious by overheating marks on the PCB.
This was likely just a random part failure not a design issue for this model, as the replacement runs just barely warm. Adequate heatsinking is provided for both regulators, but something i don't like is that they're right next to each other.
Overall build seems good quality, physical, acoustic and electronics-wise. They sound pretty darn good too, except a slight background hiss. Should also give a slap in the face to "audiophools" - most music is mixed on those or equivalents, and they use basic, humble, slow 4558 opamps and LM3886 chip amps for power amplifiers...
Design: Each monitor is stand-alone, active bi-amplified. It accepts 1/4" TRS jack or XLR inputs. It has a regular mains transformer power supply, 2x LM3886TF for power amps and NJM4558 opamps in the signal section.
Fault behavior: The affected monitor didn't light up the Yamaha logo on the front and did not produce any sound.
Diagnosis: Mains fuse fine, main power rails fine, no DC offset at the output of the power amps, speakers fine. So it had to be something in the signal path.
Fault: Missing +15v rail for the signal section.
Culprit: KIA7815 regulator on the main board, also obvious by overheating marks on the PCB.
This was likely just a random part failure not a design issue for this model, as the replacement runs just barely warm. Adequate heatsinking is provided for both regulators, but something i don't like is that they're right next to each other.
Overall build seems good quality, physical, acoustic and electronics-wise. They sound pretty darn good too, except a slight background hiss. Should also give a slap in the face to "audiophools" - most music is mixed on those or equivalents, and they use basic, humble, slow 4558 opamps and LM3886 chip amps for power amplifiers...
) and no signs of stress were noticed.
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