Korg i5s - Strange Sound

[nrcslim89]

Hello people, I have one Korg i5s, that makes a strange sound every time.

Sounds like impulse delayed explosions, some times after some time goes away and come back again rising his volume...
Desturbing a lot the correct function of keyboard.

I already change all capacitors from main board, and change the amplifier IC for new one from amplifier board because sometimes the sound only works on one speaker at the beginning (Now fixed).

But the impulse sound still all the time here.
I try to find something online but no lucky about this issue, could anyone help me to discover what kind of component or IC I need to check and is possible to cause this?

Thanks for all

[petehall347]

Re: Korg i5s - Strange Sound

transistor breaking down maybe .

[nrcslim89]

Re: Korg i5s - Strange Sound

transistor breaking down maybe .

Thanks for your reply, should i change the two transistors i have on amplifier board ?

I have 2 NPN Transistors
2SC2785

[petehall347]

Re: Korg i5s - Strange Sound

it could be from the power supply . hard to say really

[nrcslim89]

Re: Korg i5s - Strange Sound

it could be from the power supply . hard to say really

I don't mind to change the transistor from power supply and amplifier board but... i would like to know if the reason could be them...
Or if it could be a resistor... but there's no signal of blown component...

[petehall347]

Re: Korg i5s - Strange Sound

symptoms say transistor ..you might find it with freeze spray

[nrcslim89]

Re: Korg i5s - Strange Sound

symptoms say transistor ..you might find it with freeze spray

Hello, thanks for your support, ok, i was checking at Amplifier board and PSU board for transitors.

On Amp Board i have two "2SC2785" i already remove and put another NPN Transistor, board work and do the same...
First i try with only one changed and after i try with the two changed...
Sound keeps always...

Now on PSU... the only thing i really see is voltage regulators only and bridge rectifiers (RBA-402).
Could that be the cause?

Another point is one of the Rectifier Bridges don't have dissipator/thermal protector from factory and under it, i have a little yellow color on around solder joints... not too much but could be a clue ?

[petehall347]

Re: Korg i5s - Strange Sound

can you record the sound and post it here ?

[nrcslim89]

Re: Korg i5s - Strange Sound

can you record the sound and post it here ?

Sure, sorry my delay, I think it's easy to understand the sound but if you need more information or anything just say.
Hope you could help me.

[petehall347]

Re: Korg i5s - Strange Sound

that is a strange sound and not what i expected .
i say its like a reverb sound on a loop .
i suspect if you disconnect the input to the amp the noise will stop .
does everything work as it should ?

[nrcslim89]

Re: Korg i5s - Strange Sound

that is a strange sound and not what i expected .
i say its like a reverb sound on a loop .
i suspect if you disconnect the input to the amp the noise will stop .
does everything work as it should ?

Hello thanks for that, yes everything work fine, well for me in my opinion is the first time I try to repair one equipment like this.
But all keys work.
LCD work, seems everything full working, but the only thing it won't go is that sound, but... One thing is when I change the effects and disable them the sound almost goe away...

[petehall347]

Re: Korg i5s - Strange Sound

you might need an oscilloscope to trace where the noise is coming from .

[nrcslim89]

Re: Korg i5s - Strange Sound

you might need an oscilloscope to trace where the noise is coming from .

Ohhh, now you make still bad... I don't have one...
And there's no site with new pcb to buy.... For replace.

[petehall347]

Re: Korg i5s - Strange Sound

best you can do is check all connections and power supply voltages . and look closely for anything that looks wrong .

[nrcslim89]

Re: Korg i5s - Strange Sound

I already replace the rectifier bridges on PSU and the Big Capacitors too.
So resuming all:
Replace Amplifier IC;
Replace all Logic/Main Board capacitors;
Replace PSU Big Capacitors and 2 Big Rectifier Bridges.
Everything works fine but still having the sound always pulsing.

The only thing i can say is when i turn off all effects off, seems the sound goes away or still there but in very low volume.
Could this be from any FX IC on Main board ?

[petehall347]

Re: Korg i5s - Strange Sound

yes it sounds like its from effects .maybe corrosion on ic pins . hard to say

[nrcslim89]

Re: Korg i5s - Strange Sound

yes it sounds like its from effects .maybe corrosion on ic pins . hard to say

Thanks once more, could you please point me to something using the service manual ?



Thanks

[petehall347]

Re: Korg i5s - Strange Sound

you could try as many tests as you can mentioned in the manual and see if it reveals anything .

[nrcslim89]

Re: Korg i5s - Strange Sound

Today, i assemble the keyboard, and try to disable the audio effects.
And guess what?
Yeah the problem goes away, assuming this could be a effect.
So the problem is effects must be off, but i have to do it, everytime i turn ON the keyboard.
Seems to be a default configuration made by someone or old user.
I don't know how to save no effects.

Another thing is now i just have sound on one speaker =(

Could you help me how to save no effects and troubleshoot the malfunciontion of the speaker ?

[petehall347]

Re: Korg i5s - Strange Sound

is there a reset procedure in the manual ?