Korg Nautilus 88 No Power Repair Help!

Synth Repair
1

I bought a broken Korg Nautilus 88 yesterday for a good price. It was described to me as a no power situation, so I decided to take a chance.

Symptoms:
When the power button is pressed, some of the buttons will briefly flash, and that is all. Nothing comes up on the screen at all.

Steps taken:
-I have taken the bottom panel off and inspected each board for obvious signs of destruction. None were found.
-Checked each board for shorts. No obvious problems found. Outputs 15v to the panel/audio board and 11.5v to the mainboard (I didn’t see a -15v output, if that is a necessary voltage).
-Powered the Nautilus on with the panel off. Mainboard comes to life and the CPU gets warm.
-Hooked up and looked through each board with an IR camera. One hotspot found on the power distribution board on D1. Replaced it, but no change in behavior.

The last time I had an issue like this was on a 3d printer, and it ended up being a busted diode. I haven’t found any smoking gun as to why this unit won’t power on! If anyone has any advice/tips/ideas, please let me know!

2

I would disconnect any ribbon connector and reconnect. Ribbon connectors even when plugged in well do not get a good connection.its a freebee check!

3

Hi, I have a Nautilus 61 and have a similar problem. When I press the button to turn it on nothing happens.

This happened suddenly, used the night before and the next day when I tried to play at home I couldnt use it.

I replaced the power supply board and the board that has the switch.

If you know something about how to resolve this please let me know.

Regards

4

kml1989: before you pull the mainboard, isolate the supply. The Nautilus 88 runs an internal switch-mode PSU off the IEC inlet, and the front-panel power button is a soft-touch tact switch feeding a standby line, not a hard AC interrupt. Meter the inlet first, then the fuse and the standby 5V at the PSU header with the switch depressed.

No standby rail means the PSU secondary is dead: inspect the electrolytics on the secondary side for bulging and check the 3.3V and 5V regulators for shorts to ground. If standby is present but the main rails never latch, suspect the panel ribbon or the tact switch itself; those switches oxidize and read open after a few years of dust.

Do not reseat the panel ribbon with power applied, and never probe the primary side with a grounded scope (that chassis is not isolated). If you end up swapping the mainboard, internal programs and combis go with it, so pull a full sysex dump first through a modern Web MIDI tool like the Web MIDI SysEx tool in Chrome once it boots.

What DC voltage do you read on the standby pin at the PSU connector, and does it collapse when you press power?

5

The only voltage I am getting is 15v to the switch. Pressing it collapses that to nothing. None of the regulators are shorted to ground, but they also never output any voltage whatsoever. The input pins read something like 60v DC, so I now suspect the power supply is fried.