KORG iS50 Piano Keyboard: Low Phones/Line Out

[antonov62]

Hey everyone!

My KORG iS50 has a volume issue where the internal speakers are only acceptable above ~50% on the master slider. What's worse is that the headphone (phones out) and line outputs are extremely quiet, even at max volume. Both left and right channels are equally affected.

Here’s what I’ve checked:
Voltages: Vcc to DAC section measures ~5V, MUSB (mute pin on the DAC) measures ~4.xxv, and the 2 op-amps show ~9V
Master Volume Slider: Resistance ranges from single-digit Ω to ~11kΩ (seems functional).
Visual Inspection: Capacitors on the main/speaker boards look intact, no obvious damage.

Since the signal to the speaker amp taps from the headphone output circuit, I suspect the issue lies on the mainboard before this split?

Question:
What specific measurements or components should I check next to isolate the fault?


Any guidance on this would be greatly appreciated!

Thanks!

Attached: pic near the output area on the mainboard, speaker amp board and the schematic.

Elektrotanya for electronics experts

Electronics forum for electronics experts to repair defective appliance.

elektrotanya.com

 

[roughshawd]

If you keep your voice down, and not listen to loud obnoxious noise all day, your ears wouldn't be so sensitive... maybe its not made to be loud, only headphone volume... that is very common in todays studios.