Yamaha Keyboard P-95 repair

MisterBill2

Joined Jan 23, 2018
8,441
A "loud static sound" is not really descriptive enough. Crackling noises are most often caused by poor connections, while a distorted hum is more likely caused by an open ground connection.
Does the noise persist, or is it only for a short time?
 

dl324

Joined Mar 30, 2015
12,790
Welcome to AAC!
However, after I power cycle, there is loud static noise from two speakers. Key still make sound. No sure if a new part is broken or I accidentally touches something
It's probably a bad capacitor. Or possibly a bad soldering job on a replacement.
 

Thread Starter

lby0001

Joined Jan 12, 2020
11
A "loud static sound" is not really descriptive enough. Crackling noises are most often caused by poor connections, while a distorted hum is more likely caused by an open ground connection.
Does the noise persist, or is it only for a short time?
The loud static noise persists. Starts after the "click" sound. The noise sounds like AC noise. Also, when I power off the piano, there is a loud "bang" sound.
 

dl324

Joined Mar 30, 2015
12,790
Not true. Before replacement, the three I replaced were shorted.
That isn't the only failure mode for electrolytic capacitors. Most fail opened because they short and explode. Capacitors that dry out could behave as lower value capacitances before they get to the point where they're completely ineffective.
 

Thread Starter

lby0001

Joined Jan 12, 2020
11
That isn't the only failure mode for electrolytic capacitors. Most fail opened because they short and explode. Capacitors that dry out could behave as lower value capacitances before they get to the point where they're completely ineffective.
My P95 is 8 years old. Maybe it is time to get a new one. Ahh........
 

dl324

Joined Mar 30, 2015
12,790
My P95 is 8 years old. Maybe it is time to get a new one. Ahh........
I had an 11 year old DVR stop working. I considered getting a replacement, but a unit comparable to what I had cost twice what I paid and most of the comparable units were refurbished models of the one I currently have.

For less than a dollar, I replaced 4 caps in the power supply section and, hopefully, will get years more service.
 

JoeJester

Joined Apr 26, 2005
4,390
Testing a capacitor for a short condition is started by a particular set of observations in the troubleshooting process.

Electrolytics also have increased ESR ... which isn't a short condition, or a change in value condition. it's a n electrical leakage condition.

You have a crackling noise. You can probe the components you replaced to see if you can force a change in the symptoms. You may even see a poor connection by inspecting the solder side of the PCB.
 

Thread Starter

lby0001

Joined Jan 12, 2020
11
Testing a capacitor for a short condition is started by a particular set of observations in the troubleshooting process.

Electrolytics also have increased ESR ... which isn't a short condition, or a change in value condition. it's a n electrical leakage condition.

You have a crackling noise. You can probe the components you replaced to see if you can force a change in the symptoms. You may even see a poor connection by inspecting the solder side of the PCB.
Sorry my previous noise description is not accurate. The sound is more like a constant and loud hum in background. It is like loud white noise sound. At the same time, keyboard is still working.
For C216, C217 and C112 I repalced, when I probe them, no changes on noise. How do I debug? Thanks
 

dl324

Joined Mar 30, 2015
12,790
For C216, C217 and C112 I repalced, when I probe them, no changes on noise. How do I debug?
It might be a cap that's failing (high ESR and/or lower capacitance) on the power supply. You can troubleshoot by putting a good cap across any caps that you suspect. Make sure you don't short anything. I'd use a couple test clips.

If you do this, check the voltage rating on the suspect cap so you have an idea of the voltages you're working with. It goes without saying that the good cap should have the same or higher voltage rating. Also don't make it huge compared to the original.
 

JoeJester

Joined Apr 26, 2005
4,390
First, what you called a hum sounds more like motorboating. That is typically caused by decoupling capacitors on the amplifier's power connections. Values would be less than 1 microsecond on the capacitor typically.

The click at the end, may or may not be caused by the decoupling.

I'll have to look to see if I can find an earlier version yamaha keyboard to get a look at their amplifier design. It wouldn't surprise me if yamaha used the same circuit in a number of models.
 
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