Clavinova 240 Electric Piano PCB - replace capacitor - Page 1
Forum section: electronics / repair

author: einsteinsbarber
author_rank: Contributor
timestamp: August 12, 2025, 07:54:34 pm
content: Greetings - new user here. Performed a basic clean & repair of keyboard action on my medium-high level electric piano.All good - except it is now a mute piece of furniture. Re-opened the cabinet to find a small electrolytic capacitor had been wiped off its landing pad on one of the PCBs. I took photos before attempting to re-solder it. The re-solder although not perfect, was good enough in my opinion. STILL MUTE.So I researched replacement caps. The search led pretty quickly to Mouser.com. However, the new cap appears to be a bi-polar cap rather than the original neg polar cap from the PCB. The new cap has a spec sheet that states Bi-polar. All other specs are identical viz. 10uF 16V SMD 5mm dia (except 0.5mm of height on the cap - a non-issue given space available inside the piano).QUESTION - am I going to regret replacing this neg-polar cap (see jpg) with an identical spec bi-polar cap? Or should I hunt high and low for a polarised cap from Mouser (they are actually Panasonic caps I believe).Just for context this is a 240V AC line voltage piano, but the voltage on the PCB is 16V DC. I am not einstein, but I believe the original AC line voltage to be irrelevant to this question.Any input greatly appreciated. I do have access to electronics specs from the Clavinova Manual for this particular part if anyone requires it. Yamaha Australia I somehow doubt would ship me a .50c capacitor if I could even find their parts department. This is a 15 year old model - but built to last like most Japanese manufactures.

author: Swake
author_rank: Frequent Contributor
timestamp: August 13, 2025, 09:33:48 am
content: The cap in the second picture looks like a standard 10µF 16V electrolyte cap. 5mm size is pretty much standard too. Any brand is ok. You could go the Aliexpress or ebay route to find cheap alternatives that are good enough. The real voltage on the board in that place is 5V according to the schematic.ok, went to look after the service manual and found it on ElectroTanya. File is too big to attach herehttps://elektrotanya.com/yamaha_clp-240_clp-240m_clp-240c_sm.pdf/download.html#dlPage 32 top right contains your capacitor located on the PCB.Page 112 zone M2 there you find C1 in the schematic.I have not been digging deeper, this cap might be the cause of the muteness, but.... I don't think so. Only keys G4 to C7 should be impacted if at all. Also if the leads where still firmly attached on the can when you soldered it back in place then I doubt it is broken as your piano worked fine before.Check for other things like unplugged/reversed connectors and dead fuses.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 13, 2025, 10:34:46 am
content: Check there is MIDI coming out of the MIDI socket when you play keys.You can do this with a LED in the socket which will flash (faintly, more so if you press loads of keys at once)If not, the piano is not receiving the key press info from the keybed - most likely a connector, unlikely that capacitor.

author: einsteinsbarber
author_rank: Contributor
timestamp: August 15, 2025, 12:33:53 am
content: Thank you for taking the time to look at this. I do have the service manual and yes, have found the cap just as you state. I am very interested to hear your views about why the keyboard went mute - particularly if that cap on the 'H' PCB would just affect the keys G4-C7. That makes sense to me. The problem is I do not have enough grasp of overall PCB circuitry to make these deductions - but I am a mathematician who enjoys solving riddles.In order to make these cleaning & repair adjustments, there are many steps - and indeed several multi-pin connectors need to be unplugged to remove the keyboard to a bench. I was very careful about replacing these multi pin connectors - but there is always the chance something has failed to reconnect, that is not visible to the eye.I have also checked every small barrel fuse I can see - no matter which board. However I am only using visual inspection.I DO have a multimeter - not super advanced but mid grade. If you could explain briefly (or point me to a weblink that explains it) how I could use my multimeter to check1> connections across PIN connectors - or2> check the continuity in fuses while they are in placethis would allow me to be more forensic than simply seeing with the eye and smelling for burned caps.If I am going to use the multimeter to check for continuity in pin connectors or certain wires, I am anxious about the fact the line voltage to this piano is 240V. To use the Australian expression - this is 'bitey' voltage.I realise there must be an early conversion to a DC voltage - but I have not been able to locate it in the Service manual. If this is obvious to you, maybe indicating the position and page of the manual where I can see the DV side of the voltage? I do not wish to be thrown across the room. Also, which DC voltage setting should I select on the Multimeter - you mentioned 5V but would it be safe to regard it as 16V on the board?apologies for many questions - I would love to solve this problem and I know it is not THAT complicated.

author: Kean
author_rank: Unknown
timestamp: August 15, 2025, 02:00:50 am
content: First... WOW, that service manual is really excellent!Looking at the block diagram on the last page of the service manual, all the 'bitey' voltages are between the AC input and the MA80S PCB. Search the manual for the word transformer if you want to see where that is, but it is just forward of the FU60 PCB which has the AC input connection. The circuitry around it is shown well on the second last page.On the FU60 PCB there is three fuses, but they don't all get used depending on the voltage selector position. If any were blown, you probably wouldn't see any signs of life.So stay away from the FU60 PCB when the unit is plugged in or powered on, and everything beyond that should be below 30V, and DC, and isolated from mains so pretty safe.I would start by checking voltages on the MA80S PCB, as this PCB also contains the power amplifier. Primarily the voltage that amplifier, which would be at the big capacitors C5, C6, C7, & C8. It doesn't seem to have obvious test points though so you'd need to look at the various diagrams to identify the best place to measure - probably on the connectors to other boards.Check the cable between MA80S and NET1 PCBs as that carries the speaker connections.Also, check that this isn't just the muting feature of the EQ that somehow got enabled. Search for the word MUTE in the service and operation manuals.

author: einsteinsbarber
author_rank: Contributor
timestamp: August 15, 2025, 05:52:08 am
content: Thank you Kean, for these suggestions - exactly the kind of insightful ideas I was hoping for. I will be working through them when I have access to it again, in about 10 days.Yes, I figured with the level of detail in that manual, I could solve this if only I had the EEV chops. That's where your valuable contributions come into play.Some of your refs are almost over my head, but I will work through them.For any others from this forum who may have had trouble with the elektrotanya download link, I have placed the full manual together with some relevant photos and notes here all in one place....https://drive.proton.me/urls/V915QD7394#J1lCgUzDz8jzThanks for taking the time - much appreciated.

author: Kean
author_rank: Unknown
timestamp: August 15, 2025, 06:30:28 am
content: Quote from: einsteinsbarber on August 15, 2025, 05:52:08 amNo worries. I was curious to look at the manual, and although I was limited in time I thought it was useful to provide some info rather than none.You can always do additional research on any terms I mentioned that are not clear, and you're welcome to ask more questions.Other members here may have additional insight, but checking fuses and measuring power rail voltages is practically always the best starting point.

author: Swake
author_rank: Frequent Contributor
timestamp: August 15, 2025, 06:31:28 am
content: Agreed, the Yamaha Music Instrument service manuals are amongst the best you can find. Very detailed and precise.It sounds obvious but I prefer making certain: When checking fuses or connections (manually or with the multimeter) you have to unplug from the mains. That is unless you want to experiment that 'bitey' feelingDouble checking the fuses and connections for continuity with the multimeter is certainly a good step to take. Here the link to a very basic video:If your multimeter does not have a continuity mode you can use the lowest resistance mode. A fuse is basically a very fine wire with a very low resistance (a couple Ohms maximum).Could you advice what make/model multimeter you have? We might be more precise in terms of what settings to choose on the multimeter.Some questions to better pinpoint the issue: Could you describe the fault with more precision please, is it just 'mute' and anything else seems functional or are more things not working? Are the display and other LEDs still showing coherent information? Are you using the build-in speakers only? Do you have the possibility to connect an external amplifier and speakers? Did you interface with the computer and is that still working?

author: Kean
author_rank: Unknown
timestamp: August 15, 2025, 06:42:17 am
content: Good points. I meant to ask what DMM the OP has, and also if any sound using headphones.As it was presumably working fine before the cleaning, I'd suspect either a connector issue or some operation setting like Mute or volume control has got changed or is malfunctioning.I've never worked on one of these, but with those docs and some patience, I don't imagine it will be too hard to resolve.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 15, 2025, 09:07:53 am
content: Get yourself a LED, any LED, it doesn't matter. High Brightness may be a good idea.Go to the MIDI OUT socket and push its legs into the two holes either side of centre.(or solder it to a 5 pin DIN plug for future use)It will only work one way round but the wrong way won't damage anything, it just won't light.Then press some keys a lot and it should flicker.This will test the entire keyframe system, and if it works you can look for some other reason the piano is not outputting any audio.The only keyboards I have knowingly come accross that don't have the MIDI out socket ALWAYS ON are some Nords.But you need to show this working anyway to ensure at least the keybed is sending data to the CPU.Alternatively you can send MIDI into the piano and it should produce audio if the settings are correct, but this is not as much of an ALWAYS ON scenario and could lead to a false negative.

author: einsteinsbarber
author_rank: Contributor
timestamp: August 15, 2025, 03:05:14 pm
content: Thanks AR - your MIDI OUT technique seems like a creative approach to isolate the issue. I will try it as soon as I can get face to face again with my keyboard. Sorry to be a bit slow on understanding this - I do have a strip of 12V LEDs in form of a lighting strip - would that serve the purpose? It's just surplus from an under cabinet project.Is there any way to detect MIDI output with my multimeter? Or even a 12V auto circuit testing light (has pos & neg leads).btw - the earphone jack is dead also. So its not the wiring to the speakers that's compromised. Seems to me there is no audio output signal coming from the frame - so I if your MIDI OUT produces a POS result, then that would point me towards the audio circuits.Will post results here .... thanks

author: einsteinsbarber
author_rank: Contributor
timestamp: August 15, 2025, 03:19:56 pm
content: Yep.. I have never tested or tinkered with power on. Which is why it's a total pain to have to dismantle and reassemble (in large part anyway) before checking results.Re: pinpointing. No output via earphone. No sound from 'demonstration tracks', nor midi stored in memory (these models have a limited midi storage memory to allow practising etc...).The instrument panel lights up - all function buttons seem to work - but nothing that involves sound.I have tried the Yamaha 'factory reset' technique - nada.My multimeter is pretty much the same level as the one in the video - mid-level I would say. ($50).I now have some pretty specific suggestions from you 3 - and am definitely not going to surrender and list it on FB Marketplace. It's a fine instrument and well designed - has been very well looked after.Now very keen to get back and follow these leads (literally). Bedankt.

author: einsteinsbarber
author_rank: Contributor
timestamp: August 15, 2025, 03:27:28 pm
content: And just to re-iterate - those midi stored tracks, and the demonstration tracks stored in memory show indicator signals that they are processing. You can see they are 'playing' via the display panel - just no signal reaching either onboard speakers or headphone jack. I have not connected AUX speakers - could with a little effort, but I rather expect the AUX will also be out of the loop.

author: themadhippy
author_rank: Super Contributor
timestamp: August 15, 2025, 04:26:30 pm
content: you checked there aint a mute switch or speaker on off switch that got knocked during dissemble ,pedals plugged in the right holes?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 15, 2025, 06:50:38 pm
content: Ah, I forgot about the Demo tracks as I rarely use them to troubleshoot, but yes these should also be ALWAYS ON and should always appear on headphones at least.Note the headphone socket will often cut out the speakers as there is a switch in the socket that does this, so headphones is probably the best place to monitor whilst fault finding, in case this switch or the circuitry it activates is the actual problem.Some keyboards do have a separate switch to manually switch off the speakers as the MadHippy suggests.As for MIDI, it uses 5v to drive an Optocoupler in the receive device that is an LED and photo transistor.So really you need to replicate this with a single low powered LED, not a huge 12v array which it will not drive.It is a current loop - it supplies a small set current, not a voltage, so measuring voltage with a voltmeter will probably not show you much activity.

author: einsteinsbarber
author_rank: Contributor
timestamp: August 15, 2025, 09:59:19 pm
content: ✅

author: einsteinsbarber
author_rank: Contributor
timestamp: August 16, 2025, 02:56:36 am
content: MH - Working on your mute angle - I notice p 114 of the Service Manual - block diagram - has no fewer than 12 references to MUTE - with various directional arrows - anyone care to suggest a breadcrumb trail I could follow here? What would I be looking for as I check these? And can I actually find these locations?Have attached P 114 to this post - the MUTE search results highlighted in RED. I could only find 9 of 12 listed.

author: einsteinsbarber
author_rank: Contributor
timestamp: August 16, 2025, 03:03:08 am
content: And referring to the Speaker OFF switch located near the Headphone Jack - yes my Clavinova does have that switch - and it is in the SPEAKER ON position - checked it - slid it back and forth a few times.

author: amyk
author_rank: Super Contributor
timestamp: August 16, 2025, 06:43:35 am
content: Quote from: einsteinsbarber on August 15, 2025, 03:27:28 pmThat's a good sign that whatever is causing the problem is not on the "input" side, and you'll need to trace the signal from the DAC to the output to see where it disappears. Since you didn't mention you have a scope, you can use a DMM on ACV range instead and look for the presence of a voltage when it's playing. Pins 1 and 3 of CN7 on the DM board are just one opamp away from the DAC, so check for signal there first. From there you can follow the signal through the volume control (VR401), back through the AJACK board and out to the EQ board.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 16, 2025, 07:55:19 am
content: Often you will find the volume pot or slider is quite accessible and a good place to start looking for the audio signal.

author: einsteinsbarber
author_rank: Contributor
timestamp: August 17, 2025, 11:56:00 pm
content: Quote from: amyk on August 16, 2025, 06:43:35 amThank you amyk for laying this out - I will be following these breadcrumbs when I get it pulled apart again...

author: einsteinsbarber
author_rank: Contributor
timestamp: September 06, 2025, 06:21:57 am
content: Finally made it back to where my Clavinova and I are in the same room... In the next few days I intend to dig into this again with the aid of suggestions from eev.bloggers.Without dismantling anything yet, I have seen that both the Demo Songs (50 classical pieces saved on the piano) and the User Songs (3 custom tracks available for saving by User) actually do play sound from speakers. This suggests that the electrolytic cap which I repaired and whose integrity I doubted, is probably OK since all these recorded songs etc are playing perfectly. The problem lies in the key-press -> speaker path.So after checking all plug re-connections, I'll be checking the signal path from key being pressed to sound at speaker - amyk in light of this do you still suggest starting at PINS 1 & 3 of CN7 of the DM board, etc as you laid out before?Will be wading in in next few days and will post whatever I find... thanks again all who commented this thread...

author: Swake
author_rank: Frequent Contributor
timestamp: September 06, 2025, 07:27:00 am
content: The world of electronics looks complicated but generally it isn't.... This feels like a simple problem to solve, don't go over complicated and search for simple causes first.The keys are not making notes but all the rest seems to work -> the issue will be found in the interface between the keys and the processer -> There is a connector in between on board "GH3 EBUS M" which is the board of the middle keys, check that first. (top middle of page 112, and attachment here)These are now your next steps to follow one step at a time: In between each step you test if that solves the issue or not.- Are the plugs of the keyboard boards and the one going to the DM board in the correct connectors and plugged in firmly, not reversed? Eventually unplug and plug back in. Damaged/bend wires or pins? Solder joints of the connectors on both keyboard and DM board ok?- With the piano powered off: Measure connectivity end to end with your multimeter for each of the wires in that center connector.- Power on the piano and measure if there is 5V on the connector between GND and +5V; there are 2 pins for each.- On the same middle board "GH3 EBUS M" remove both yellow connectors marked A and B (see attachment). If there was no 5V in the previous step measure again. If there is 5V now then test if the middle keys work now.- Only if the middle keys work plug back in the left connector and try again.- Only if the left and the middle keys work plug in the right connector and test again.- Now please report your findings.

author: amyk
author_rank: Super Contributor
timestamp: September 06, 2025, 08:15:54 am
content: Are you saying the problem has changed? Previously you weren't gettinganyoutput from the speakers, even with the demo songs. Did you do anything to cause this change?Agree with the above post that the keys are now in question.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 07, 2025, 12:38:30 pm
content: I must have misdiagnosed the problem after the cap repair- apologies for not realising that in fact there was output from recorded digital content after I soldered back the cap. All I can say is I was preparing for travel and must have jumped to the conclusion there was no improvement, in haste. I definitely heard no demos before I noticed the elec cap had been wiped from PCB, but post repair I must have had volume down or mute button on - and somehow reasoned the cap repair had not worked. Given there is demos sound at speaker, I now presume that cap is functioning normally.So the current status is - as stated, no sound on any keys being pressed. However, recorded on board tracks DO play, and they play across entire range of keyboard.Do you still suggest checking the PINS you mentioned - given I am now looking only at the keyboard -> speaker path, and I know the speakers are in good shape.Thanks again.

author: Swake
author_rank: Frequent Contributor
timestamp: September 07, 2025, 12:51:36 pm
content: No worries, for now please follow the 'guide' in my previous message.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 09, 2025, 01:34:50 pm
content: This is the DM PCB I will be testing - it is basically in the heart of the piano and the CN10 goes out to the GH3-M bus CN2 that you reference in your previous pic. All wires and pins good on the GH3-M PCB. Plugs 'A' (CN1) & 'B' (CN4) on GH3-M have been removed & reconnected to be sure they are OK. So I will now test the voltage on the CN10 pins here on DM as in photo.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 11, 2025, 01:11:52 am
content: All tests passed. Continuity on all connectors on DM PCB - photo in post. 5.10V on relevant pins at CN10 on DM, which connect to CN2 on GH3-M.Next step - I will reconnect keyboard and follow amyk suggestion to check for voltage at CN7 on DM when keys are pressed. Not 100% sure whether it should be ACV or DCV but will select ACV 20V and see what gives. Pls advise if MM should be set to 240ACV - I doubt it.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 11, 2025, 03:38:36 am
content: Update... powered on test of CN7 at DM. Pins 1 & 3 tested with ACV set to 20. Played demo songs - audible through speakers. During play, variable voltage from .10 - .40 V readings fluctuating while songs playing. As expected. When demo sings not playing, Pins 1 & 3 reading 0.00.Keyboard connected - Pins 1 & 3 registered 0.00 while keys being pressed on keyboard. So there is no signal emanating through GH3-M CN2 to DM-CN10.I have to conclude either there is absolutely no physical contact happening to generate a signal - which I find difficult to believe when I inspect the mechanism.OR - the wiped electrolytic capacitor (10mF 16V) located at C1 on GH3-H which I showed in my original post, and which I resoldered back in place, is somehow stopping signals travelling to CN2 on GH3-M.Note there are caps on each of the 3 GH3 PCBs, located at C1. The other 2 are in good shape.Next step - I have a replacement cap (bipolar but otherwise identical 10mF 16V) and I will replace the wiped one before testing one more time.

author: Swake
author_rank: Frequent Contributor
timestamp: September 11, 2025, 06:54:30 am
content: Please confirm you measured the 5 VDC on connector CN10 on the GH3 EBUS M board (not on the DM board side, I know it is only a wire away, but that makes a difference). Preferably measure on the PCB side where these are soldered.Do another measurement with the multimeter over the 2 legs of the now famous C1 cap. You should have 5 VDC too.If you have the 5 V on the GH3 EBUS M board:While your piano is made out of 3 boards with keys, these are all 3 the same boards with the exception of a selector jumper (R10 or R11) on those boards. Before doing something with the cap:Let's test with only the middle board connected. -> On that middle board (not on the other boards) disconnect the 'left side keys' board GH3 EBUS L and also disconnect the 'right side keys' board GH3 EBUS H. Now please try if there is music from the middle keys and report.Sorry, short message because not much time today.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 11, 2025, 08:00:33 am
content: If you are not getting any electrical changes then I would suggest you may have taken the contacts system apart and not put it back properly.Perhaps the contact strips are the wrong way round (not usually possible to do this), or the contact PCB's are not seated correctly so the contact strips don't actually touch them.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 12, 2025, 05:20:06 am
content: Quote from: Audiorepair on September 11, 2025, 08:00:33 amIts a tempting theory and I also thought that of course initially. After the 3rd dismantle & remantle however, I don;t think that's the case. There are subtle yet reliable locator marks and shapes which register the placement of those delicate rubber connector strips. First time round I did not see them - 3rd time round I think they are all well slotted into their grooves, and aligned with their markers.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 12, 2025, 05:30:14 am
content: Quote from: Swake on September 11, 2025, 06:54:30 amAll tests performed and all positive - but no sound in press keys mode. No sound in isolated GH3-M mode either. All 3 caps, 1 on each PCB show 5V across terminals when powered on. Doesn't necessarily mean they are functional though I gather - I would need to disconnect them from board to truly test them.Took the PCBs off yet again to inspect rubber contact strips and their correct placement vis-a-vis the correct area on the back of the PCBs. Seems to me there is physical contact but it's quite difficult to verify that visually once the PCBs are re-attached. There are specific registration marks - I made sure all marks are correctly aligned.The mystery continues - pretty sure it's an electrical issue given the total silence on all keys. Once again all onboard music plays perfectly - demo function, user stored tracks, 50 onboard songs etc... btw they play even when the keyboard is disconnected... further directing me to the GH3-BUS as the issue.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 12, 2025, 05:54:09 am
content: You can make the contacts operate with a finger instead of the keys, albeit with random results.But it is well worth trying this if you can bear to partially dismantle again.Alternatively you can find the tracks that go to the pads and short them out with wire etc.There are 2 pads per key to determine the velocity of each key press. One of these, when shorted, will produce a full volume note.

author: Swake
author_rank: Frequent Contributor
timestamp: September 12, 2025, 06:19:14 am
content: Interesting results. Now we know the C1 capacitor is either working or if is is not working (well enough) it is at very unlikely to be the cause of the issue. The C1 capacitor is in parallel to the power supply. Its functions is to help the power supply locally by smoothing out the 5 VDC and providing a little local energy buffer. It is likely that even without the C1 in place everything would still work till you start playing with 20 fingers at a time in an extremely vivid tempo or something like that.On page 41 (42 of the PDF) a test program is described. The interesting part here is that you need to press 3 keys to make it work. Would you please run that test?- If you can start the test this would show the keyboard actually works and we'll have to find why it does not play.- If you can not start the test it further confirms the keys are 'dead'.Something else you can check:On the connector to the keys GH3_EBUS there is a I²C signal on pins 4 (SDA = Data) and 6 (SCL = Clock). With only a multimeter you can not analyse the signal itself but these signals will likely have a pull-up resistor and be at 5 VDC (measure between GND and one of the pins) when no keys are played. When keys are played it will likely measure somewhat lower. If you measure near 0 V then there is something wrong here.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 12, 2025, 09:29:53 am
content: Quote from: Swake on September 12, 2025, 06:19:14 amThanks for your tenacity on this - I wish I knew more about circuitry. I will get into that tomorrow - I also like Audiorepair's suggestion - just put your finger in there!!! Now that I know we are talking 5V I am getting more daring about this stuff. I will stay clear of the main power supply though.Just for clarity, what PC card has the onboard 240V AC? And at which connector when does it become 'safe'?

author: einsteinsbarber
author_rank: Contributor
timestamp: September 12, 2025, 09:38:10 am
content: Quote from: Audiorepair on September 12, 2025, 05:54:09 amExtremely practical - wondering why I didn't think of that - sounds like you have done piano surgery before. I will explore this tomorrow and report. Also very interested in your comment about FULL VOLUME because the reason I dismantled this in the first place was to try to repair one key which was playing at full volume - since I practise much of the time with earphones it was deafening and very jarring to encounter. That's what started this whole mess.When I opened up the contacts, I was quite surprised at the amount of debris in there (I don't eat toasties while playing 😂). Your comment means there was probably enough debris in that particular key to short the contact plate somehow when pressed.Anyhoo... I will explore the finger assist tomorrow. Thanks for the suggestion 🙏

author: Swake
author_rank: Frequent Contributor
timestamp: September 12, 2025, 09:51:40 am
content: Unsafe: FU60 Module (in the middle of page 114 in the PDF) that is: the power cord; the power switch; the line filter with fuse; the primary side of the power transformer. These should be separate from the other boards and maybe also shielded from the rest.Everything else is should be safe to the touch because according to the schematic the max voltage is the one going to the amplifiers and should be 22 VDC. All the digital stuff (including keyboards) is 5 VDC, entirely harmless.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 12, 2025, 10:39:44 am
content: If you notice, the rubber key contact strips have two contacts per note, one longer than the other.The time difference between the two contact strikes is proportional to how hard you hit the key, which the keyboard translates into Note Volume.If one contact ceases to work or gets too dirty, you will either get no note at all, or the note at full volume.Tapping several key contacts at once with fingers will usually produce a cacophony of noise, which is all you need to prove the keyframe is working.Remember you can still test whether the keyboard is detecting key presses simply by putting an LED in the MIDI out socket.If it is physically possible to put the contact strips in the wrong way round, then the shortest contact will always strike first, which the CPU may well convert to a No Key Press and no keys will work, neither will the MIDI out.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 12, 2025, 11:46:37 am
content: Quote from: Audiorepair on September 12, 2025, 10:39:44 amI had forgotten your reference to this, but I don't really have an LED that would work for this...I'm interested - when you say several contacts at once with the fingers - are you saying pushing them onto the PCB contacts by hand, or are you saying just touching the contact pads with your finger - no PCB involved.It looks to me like you are suggesting I remove the PCB (still connected to power) and just take the contact rubbers and push them against the PCB contact panels. That I can achieve, the LED in the Midi Out I dont think I can rig that at this time....

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 12, 2025, 12:06:20 pm
content: Yes I am saying take the PCB's out, turn on the power, then place the contact strips where they are supposed to go and then just flap your fingers all over them like the keys should do.At some point you will get a key strike which is enough to show it is working.Do not touch the black carbon contact pads with your fingers, this will not trigger a note but may contaminate or damage the pad.But if you are taking the PCBs out and turning the power on, you may as well try the "short the contacts out with wire" thing instead/as well.Try both contacts, only one of them will probably produce a strike.Don't put the wire on the contacts themselves, follow the traces to something you can attach to.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 13, 2025, 01:13:38 am
content: Quote from: Swake on September 12, 2025, 06:19:14 amTest phase did not initiate = keyboard signals not registering.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 13, 2025, 01:18:51 am
content: Quote from: Swake on September 12, 2025, 06:19:14 amSDA and SCL pin checked - both have -5.10 DCV. No change in DCV when keys are 'played'.Next step - remove GH3 Bus PCB and initiate physical contact between contact rubber strips and the PCB contact plates = 'finger assist'. 👇👇👇

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 13, 2025, 01:51:52 pm
content: I can't remember how this particular piano is assembled, but it might be that the contact PCB's are supposed to slide underneath plastic tabs on the keyframe.You may have been assembling them on top creating a space between contact strips and keys.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 13, 2025, 04:37:36 pm
content: I also seem to recall this might be the piano where you have to lift the metal hammers up to install the contact strips, otherwise the mechanism is in the state of pressing on the contacts as you are trying to put the boards back in.I use a long screwdriver and a second screwdriver to keep the hammers in the air whilst the contact strips are placed in position, then the PCBs are placed on top under their tabs I think.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 14, 2025, 10:05:40 am
content: Quote from: Audiorepair on September 13, 2025, 01:51:52 pmAudiorepair - it says you are based in England - if I lived there I would definitely be shouting you a pint or 3. The manner of replacing the PCBs was the problem -I now have a prefeclty fuinctioning Clavinova and can recoup some much missed practice.As others have stated, the Clavinova CP240 Service Manual is one fine piece of work - but at times it gets a little obtuse with side-by-side english and Japanese comments in the Fig illustrations. So I feel slightly less humiliated when I could find not one reference on the relevant Disassemble-Reassemble pages, to these little projecting tabs whose real purpose is to compress the PCB against the contact rubbers - it is far from self-evident. Pages 18-20 for anybody who is interested. Happy to post the excerpt pages also on request.May I just close by saying these specialty forums are one of the truly positive things about the internet these days - among so many drawbacks in other online corners. Many thanks for those with enough wisdom born of experience, and enough patience to bother replying to uninformed DIYs in their time of need.🙏🎹🙏

author: einsteinsbarber
author_rank: Contributor
timestamp: September 14, 2025, 10:12:04 am
content: Quote from: Swake on September 12, 2025, 09:51:40 amThe same applies to you Swake - and to all others who responded here - but particularly for your followup. Your perseverance truly appreciated - it's a form of volunteersim actually, and it speaks volumes (musical pun).May I just close by saying these specialty forums are one of the truly positive things about the internet these days - among so many drawbacks in other online corners. Many thanks for those with enough wisdom born of experience, and enough patience to bother replying to uninformed DIYs in their time of need.🙏🎹🙏

author: Swake
author_rank: Frequent Contributor
timestamp: September 14, 2025, 11:23:05 am
content: great news.While I was convinced it was something 'simple', without Audiorepair sharing experience it would have been nearly impossible to find that cause remotely.

author: einsteinsbarber
author_rank: Contributor
timestamp: September 15, 2025, 02:45:28 am
content: Quote from: einsteinsbarber on September 14, 2025, 10:05:40 amHere is the relevant section in Manual dealing with removing and replacing PCBs 🤷🏻 Thanks to all posters...