As an audio enthusiast, Audio-Technica has long been one of my go-to brands for reliable gear. Back in 2016, I bought a brand-new Audio-Technica AT-LP120-USB direct-drive turntable. For nearly eight years, it performed flawlessly. Then came last June.
While listening to a record, I noticed a subtle drop in pitch. I adjusted the pitch slider and tried tinkering with the speed controls, but the platter responded erratically. Within a few minutes, the rotation slowed down to a crawl and came to a complete stop. Power cycling the unit did nothing to jumpstart the motor, though all the status LEDs and indicators remained brightly lit. The main logic was alive, but the motor was completely unresponsive.
I decided to open it up and see if I could save my turntable. Upon opening the chassis, I was surprised by the internal layout. Rather than a simple single-board design, the LP120 utilizes a complex modular dual-PCB setup:
- Control board: Handles user inputs, pitch control, speed switching, and status LEDs.
- Motor control board: Houses power regulation, the motor driver IC, passive filtering, and BLDC drive circuits.
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| Motor control PCB showing the 3-phase stator windings and hall-effect sensors. |
Testing the power section of the motor control board immediately revealed a blown 1.5A SMD fuse. To isolate the fault on the bench, I temporarily bridged the blown fuse with a thin wire jumper and supplied 22V AC directly to the power terminal. Almost immediately upon powering on, the 7818 linear voltage regulator began heating up excessively. I quickly cut the power to prevent thermal destruction.
Measuring resistance between the +18V output rail and GND revealed a near-dead short of ~3Ω.
Tracing the +18V trace brought me to the main motor driver component: the BA6868FM, a 3-phase BLDC motor driver IC. Probing the pins of the chip revealed an internal short circuit between Pin-19 (VM - Motor Power Supply Input) and Pin-13 (RNF - Output Current Detection Resistance Pin). The chip was dead and had to be replaced.
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| Original BA6868FM IC. |
Desoldering the BA6868FM was straightforward, but Audio-Technica applied a strong adhesive underneath the IC belly during manufacturing. Even after melting the solder across all pins, I had to apply careful upward levering pressure to snap the glue bond without lifting the PCB traces. I ordered a replacement BA6868FM via AliExpress for around $5 USD.
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| Replaced BA6868FM IC. |
Removing the shorted IC allowed me to measure the raw phase outputs going to the BLDC motor winding terminals. However, checking resistance across the motor terminals yielded uneven readings:
- Pin 1 to Pin 2: ~15Ω
- Pin 2 to Pin 3 / Pin 1 to Pin 3: ~3Ω - 4Ω
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| Faulty capacitors in the BLDC driver stage. |
The output filter network is simple: clamp protection diodes between +18V and GND, alongside 220µF electrolytic capacitors and 0.1µF ceramic decoupling caps. Testing the 220µF electrolytic capacitors out of circuit revealed the real culprit: two out of the three 220µF capacitors were internally shorted to ground. Surprisingly, neither capacitor showed any physical signs of failure - no bulging tops, no leaking electrolyte, and no discoloration. They looked brand new, but internally they had failed completely.
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| Replaced 220µF capacitors. |
Once I desoldered and removed those faulty 220µF capacitors, I re-measured the motor terminal resistance. The readings immediately balanced out, yielding a healthy ~30Ω across all motor terminal pins, confirming the windings themselves were intact.
Audio-Technica is a respected name in audio, so I expected higher-tier Japanese capacitors like Panasonic, Nichicon, or ELNA on the motor driver board. Instead, the LP120 came populated with cheap, budget Su'scon capacitors. Their premature failure caused the severe overcurrent condition that blew the motor driver IC and the main board fuse.
For the fix, I desoldered and removed all three failing Su'scon 220µF electrolytic capacitors, then installed new high-grade 220µF replacement caps across all three motor driver phases. Next, I cleaned the old factory glue off the PCB footprint using isopropyl alcohol and carefully aligned and soldered the new BA6868FM chip pin-by-pin. Finally, I removed the temporary wire bridge and replaced it with a proper 1.5A SMD fuse (the original footprint was 0805, but a standard 0603 fuse fit nicely across the pads).
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| 1.5A SMD replacement fuse (0603 size fitted onto 0805 pads). |
The repair took roughly a month from start to finish - primarily waiting for the driver IC shipment to arrive. After all these fixes, the turntable is now back to spinning vinyl smoothly with solid speed stability.
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| Recovered motor driver PCB. |
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