Piano is yamaha p120. I noticed one day that sound on right channel is distorted. Now i checked every output and the resulte is same (heaphones and audio outputs(fixed lvl)) here is link to audio record https://drive.google.com/file/d/1sgvqyXYv0N5LDl6uZEBEAN5GPMXRZdW5/view . Here is block diagram of piano https://drive.google.com/open?id=1l6j4FVNfQn9Mcj1wFXbuXbn--yAsMBjS . So if someone has some assumption or experience with this kind of thread i would be sooooo grateful bcs i really love this piano.


Thank You

 

Welcome to AAC!
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Thanks.

 

Service manual here. ..

Ideally you need an Oscilloscope...

https://elektrotanya.com/yamaha_p-120_s.pdf/download.html

The Headphones and Aux out, have a separate amp.
Check on page 60, IC103,preamp chips.

Check page 61, IC13, IC22 preamps.

 

Thnak you so much for replay ..... Hmm i dont have Oscilloscope is there any other way ? I think that ic103 falls out of game bcs i have same results on fixed lvl ( that hiss in sound ) . From DAC it goes from ic13 -> ic22 -> ic101 and form there one R L line goes for volume sliders to ic103 to headphones and other goes straight for fix lvl outputs.... So u think that its preamps problem?

Thanks

 

Do you have any kind of audio amplifier available? Either a stand alone amp, or a receiver with 'Aux' or 'CD' inputs? You could try using that as a signal tracer.

Connect a cable (usually an RCA connector) to one of the amplifier input connectors. Turn on the amp and select the used input. Touch your finger to the input cable and you should hear a noise and maybe some hum from the output of the amp.

Now use that input to the amp to trace the signal through the piano. I's start by listening to the signal at TP187 and TP188 (outputs of IC13) on the DM board. You will want to connect the shield of your test cable to a chassis ground on the piano.

If the signal sound clean at those points, go on to TP101 and TP103 (the inputs to IC101) on the AJACK board. Then look at the outputs of IC101 <- these should be the same as your fixed level aux outputs.

[Note that when you are using your test lead, you may be upsetting the bias on the op-amps in the piano, so don't expect the piano outputs to be clean when the test lead is connected.]

 

An alternate troubleshooting technique is to simply measure the dc voltages on the IC pins (IC13 and IC101) comparing the left and right channels. If you find any differences, you can post them here and someone will offer an opinion.

 

Thank you for replay ..... So i probed with aux line and got that same hiss on those points ( tp187,tp188 one of them ) ... Im not sure what dc voltage to measure, between what points on ic13 . Here is pic of that spot on board https://drive.google.com/open?id=1xt3GHZaWLxn5jpCN_ObyvjX56wA6rty9 . Should i try yo probe direct from DAC ?


Thanks

 

When you probe with the aux line to an external amplifier, you need to have some signal coming through the piano. You should hear whatever is being played though the external amplifier. When measuring voltages, connect the negative voltmeter lead to a ground point, such as the shell of a headphone jack or the outer shell of one of the 'aux' outputs.

On both IC13 and IC101, probe and record the voltages on all the pins. Just be careful not to let your voltmeter probe slip and short the pins.

 

Yes i played demo on piano and with probe outputed it to external amp. I measured voltages and on all pins of ic13 and ic22 https://drive.google.com/open?id=1NZmbnUlAqRPickAB8fRi9CpxPZsvqNE0 .... I rly dont see point in checking ic101 when output of ic13 goes into its input but problem is present on ic13.

Thanks

 

So when you are probing with the external amp, the signal at TP182 (left channel) sounds OK, but the signal at TP181 (right channel) is distorted, correct? Then yes, try probing directly at the DAC output, TP173 and TP174.

If the signal is clean at TP174 and distorted at TP173, then you have a DAC issue.

 

Yee i tried to probe from DAC and even from ic22 but signal is to weak i would need stronger amp ( this is 30w ) its barely hearable I hope problem is DAC or pre amps bca i found parts online but if its that main Yamaha chip then bye bye.
Thank you so much for replays .