Hi all - new to forums. Trying to get some help getting a XP-10 working. Picked it up filthy in a pawn shop for cheap with no power supply. Got it home, cleaned it up, hooked up a 9V 1000mA power supply - got a garbled display and no audio output - headphones or line out.
Almost just called it a lost cause, but I hooked it up to MIDI and confirmed all keys work. Downloaded user manual, and I could see through the garbled display that it appeared the logic section was working. Maybe fixable?
Finally found a schematic on the internet. I see the display is a standard 16x2 LCD, with the wiring slightly jumbled. I can handle that - if I can get the rest working. Further tests - I was able to get it into demo mode, playing some songs - with volume maxed and headphones on, I could just barely hear it working.
Found this forum searching for answers - someone had an excellent writeup on troubleshooting a XP-50 with similar problems - but the DAC and mute circuit is a bit different on the XP-10
Background - I'm an embedded systems programmer with some knowledge of circuits, but weak in analog electronics. I know how to program a 16X2 LCD, but 'simple' op-amp stuff confuses me.
Anyway, with every output out, I would suspect the muting circuit, or the amp. Any suggestions on what to check?
It looks to me like the muting circuit works by sending the signal to ground through Q12, Q13,Q14,Q16. I checked DC voltage, and each transistor has 0 volts at pin 1.
Both op amps have 0 and ~8V at the rails.
If I touch the caps on the volume board, I get loud hum, which responds to the volume control, which makes me think perhaps the amp is working?
I'm down to shotgunning the electrolytic caps, and if that doesn't work, I guess I have a decent MIDI controller. Any suggestions?
Thanks
Sam
XP-10 VERY low volume
Re: XP-10 VERY low volume
Followup in case someone else has a similar problem.
Replaced all the electrolytic caps - no change
Pulled Q16 transistor up to disable powerup mute - no change
Was just about to replace op amps, when I decided to to verify the volume slider worked just to be sure.
That was it - I don't think the sliders are available anymore, I guess I'll add a knob.
Lesson learned - check the obvious things - assume nothing.
Replaced all the electrolytic caps - no change
Pulled Q16 transistor up to disable powerup mute - no change
Was just about to replace op amps, when I decided to to verify the volume slider worked just to be sure.
That was it - I don't think the sliders are available anymore, I guess I'll add a knob.
Lesson learned - check the obvious things - assume nothing.