Electric Keyboard Piano No Sound

[ksotoszx]

Hi all, this is my first post on this forum, i will need the help of someone who knows in order to repair the old Electric Keyboard Piano that was given to me.
It is a gold star brand, model gek s350. It lights up normally, everything seems to work but it has no sound. Neither from the keys nor from the ready melodies.
-I haven't forgotten a plug in the headphones.
-The capacitor that I touch with my finger (in the picture) has no resistance, as I measured with the multimeter, but I don't know if that's the reason.
Before i attempt something on my own and possibly destroy it, i would appreciate if someone can guide me on how to fix this.
If you want more pics, i can upload, instantly!
Thanks in advance

[mon2]

Model typo?

Keyboard has part # GEK-S325 in the shared pics.

Service manual is attached.

[ksotoszx]

Model typo?

Keyboard has part # GEK-S325 in the shared pics.

Service manual is attached.

Thanks you mon2. I will check it, right now

[CapLeaker]

I would first take those two square socketed IC’s out and reseat them. Then check if all your power rails are up and running.

[Sam Scarbo]

Did you try to plug in a headphone to see if there was any sound?

[ksotoszx]

I would first take those two square socketed IC’s out and reseat them. Then check if all your power rails are up and running.

Hi, thanks for advice, i just unplug the 2 square socketed IC’s, reseat them but nothing.. Power rails seems ok.

[ksotoszx]

Did you try to plug in a headphone to see if there was any sound?

Hi, i want to try this but for now i haven' t 1⁄4 in audio jack to test..

[CapLeaker]

Hi, i want to try this but for now i haven' t 1⁄4 in audio jack to test..

Yes, because that disconnects the speaker. there is also an AUX jack to look at.
On that service manual page 4 there is a full block diagram on how this thing works. Dismiss the digital stuff for now and go straight to the TDA1311 which is a DAC. You should be able see something on the output pins with an oscilloscope if you play or strike a key.

[ksotoszx]

I have 2 questions,
a) How to test an ic (pic1)?
b) These capacitors (pics 2,3) as seen, are ok? (with multimeter shows that have resistor, except one that when i connect with to multimeter shows negative polarity resistance!?
c) Last photo is manual what to check.
Any ideas appreciated!

[ksotoszx]

Yes, because that disconnects the speaker. there is also an AUX jack to look at.
On that service manual page 4 there is a full block diagram on how this thing works. Dismiss the digital stuff for now and go straight to the TDA1311 which is a DAC. You should be able see something on the output pins with an oscilloscope if you play or strike a key.

I totally agree but I don't have an oscilloscope. With a multimeter can I see something? Thanks you.
Just unplugged the headphone cable from the board but nothing..

[stj]

if you jack the volume up do the speakers hum at all?
touch the pins of the volume pot with a soldering iron and see if you get a loud hum.

[CapLeaker]

I totally agree but I don't have an oscilloscope. With a multimeter can I see something? Thanks you.
Just unplugged the headphone cable from the board but nothing..

All you can do is to check that each IC is getting power to their proper pins. From the DAC the left and right channels are having their own circuit. Some even have their own IC. The problem is either the DAC, no data input to the DAC, or some voltage missing to an IC which handles both channels. etc. Its gotta be something common to both channels. Ummm... I suggest you borrow an oscilloscope.