Yamaha P-105 Keyboard Circuit Board SMD decoding

Thread Starter

oggy bleacher

Joined Feb 18, 2020
I'm researching repair options for this 2013 yamaha piano keyboard and this forum appears frequently with good advice and knowledgeable community.
The keyboard had intermittent functionality. Power light would come on but the instrument sound selection wouldn't default on. An instrument voice selection always came on automatically and now it doesn't. I reset all settings to default and sometimes I could turn it on and off and sound would reappear in both the headphone and on board speakers, but then the sound would disappear, but the issue isn't a headphone/speaker issue since the instrument light doesn't even come on, although the power light does come on, so I know there won't be sound because it's basically stuck in that instant between turning on and selecting the default instrument voice. No buttons work, not even the power button to turn it off. I have to unplug it to turn it off but the power button works to turn back on...though the instrument voice still is not selected. The instrument definitely was moved around a lot in a padded case and spent some time on beachfront property so it's had a full life but if I can repair it then I'd like to try.

I dug around the boards and ribbon cables hoping something would be obviously broken or loose but found nothing. I disconnected the headphone board with no change and there's no obvious bulging capacitors or corrosion but that's what I'm concentrating on.

I've decided to give one last try in identifying the SMD caps to replace since it's a common problem and the symptoms point to a main board capacitor failure. The keyboard is not really worth a manufacturer service repair so it all comes down to identifying these SMD caps, ordering them, replacing them, reassembling it and deciding what to do from there.
Sorry for the glare off the board. (I did a cursory ohm test with a multimeter and the caps that did not register any change in resistance are marked with a black marker dot. But I plan to replace all of them since I don't trust any of them.)100_3902.JPG

There are 14 SMD caps in total (a few are out of that picture frame) grouped into 6 values...(quantity):
F3 100 25 (2)
3H 100 16V (6)
3F 1 50V (2)
3l 10 16V (2)
100 JFC E43 (1)
F2 220V UD (1)

I have identified the top 4 value groups in kits such as this one on amazon https://www.amazon.com/Eiechip400pc...ywords=smd&qid=1582073619&s=industrial&sr=1-1
or, if I go the radial capacitor route,

But the bottom two in my list are coded in a way I don't know how to unscramble and the tutorials I found were in Hindi so I didn't learn much. I don't know if one in the assortment kit is compatible.

100 JFC E43 corresponds to what values?100_3906.JPG

F2 220V UD corresponds to what values? 100_3903.JPG

Another questions is about a recommended seller of these capacitors. I couldn't find a friendly looking electronics supplier (Mouser, McMaster Carr, JCarr, Arrow all looked cluttered or catering to bulk purchases.) to purchase them a la carte, so that's why I'm looking at more expensive assortment kits. I'd rather simply buy two of each and not invest more money in parts for what could be a junk unit.

So, if someone could decode those two caps for me and direct me to a supplier who will sell $10 worth of caps I would appreciate it.


Joined Mar 30, 2015
Welcome to AAC!

It looks like the caps have two different marking styles, indicating different manufacturers.

This one appears to conform to Panasonic markings:
1582084511452.png 1582084592033.png

You could try looking for similar documentation for caps by other manufacturers (Murata, Rubycon, Nippon, Kemet, AVX, Nichicon).


The middle line on these is probably capacitance in uF. The bottom line is voltage rating. The top line is series/lot number.

The series could be important. Panasonic FC are 105C, low impedance, RoHS.

I think replacing capacitors without knowing if they're bad is a waste of time and money. It's not a very good troubleshooting technique and you could end up causing more problems than you solve.

One technique for finding bad caps is to tack a known good one in parallel with the suspect. My preference is to use an oscilloscope and see if there's anything suspicious. A schematic would help with analysis.
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Thread Starter

oggy bleacher

Joined Feb 18, 2020
6.3V 100uF caps aren't included in any of these assortment packs but Mouser does have them.

The Nichicon cap F2 220V UD is decoded here. The lot number is F2. 220 is the uF...V=35V UD means low impedance.
nichicon caps.PNG

I think that completes the shopping list. Mouser took a little figuring out but they accommodated small purchases and did have everything I wanted....although I did make a mistake and ordered a 16V 220uF capacitor when I really needed the 35V 220uF variety. But I added it to the order.


This may not fix the keyboard but under the circumstances (lack of testing equipment or service shops) it's worth $15 in parts to try.

Thread Starter

oggy bleacher

Joined Feb 18, 2020
update, the parts arrived and there are two that look like there's 1 mm or 2mm difference in form factor/base. I don't know if that will affect the soldering process yet.

100 25V (2) looks slightly smaller than the original
220 35V (1) looks bigger all around than the original.100_3946.JPG
That looks like it won't fit.

The others look exactly the same form factor but the printing font is different.
Next step is replacement.

Thread Starter

oggy bleacher

Joined Feb 18, 2020
As expected, this was a fail. I replaced every electrolytic capacitor (in a messy fashion but the best I could do) and got identical symptoms. The power light comes on but no instrument voice is ever chosen. I can reset the settings by holding down the highest treble key and turning it on at the same time, but no instrument voice is chosen so I know there will be no sound. No button works except the power button turns it on, but doesn't turn it off.

There is one large blue Capacitor on a different board that I didn't change because it's the variety that usually bulges when defective. I meant to order it but never did.
Is a processor shot? A flawed ribbon cable? Another component faulty? I'm not convinced any capacitor was faulty to begin with although one did come off the board a little too easy. They were just the cheapest/easiest thing to replace. One tip I learned is to simply cut the E.caps in half and that exposes the legs to cut off. No need to desolder them.

These circuit boards are for sale for $200 which makes the choice to trash it very easy since the action is 7 years old and the replacement circuit board has no guarantee to work either. I prefer to keep things out of the landfill but consumer electronics aren't designed for longevity.

Thanks for guidance identifying what capacitors I needed. Good luck to anyone else trying to preserve or resurrect their p-105 yamaha digital piano.