Electronic Musical Instruments

Ask an Electronic Musical Instruments Question, Get an Answer ASAP!

Ask an Expert,
Get an Answer ASAP!

Electronic Musical Instruments

Name is ***** ***** and I have been asked to repair a

Customer Question
Kurzweil Mark 10 piano. The...
Name is ***** ***** and I have been asked to repair a Kurzweil Mark 10 piano. The piano has loud popping in the audio, speakers, phones, and audio output jacks. Can't seem to isolate the problem and have no service manual/schematics.
JA: Thanks. Can you give me any more details about your issue?
Customer: The piano sounds do come thru, but the popping is much louder. The volume of the pops go up and down with the main volume control. When I unplug any of the I/O connectors from the audio board, the popping (and the piano sounds) all go away-nothing comes out.
JA: OK got it. Last thing — Electronic Musical Instrument Experts generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.Category: Electronic Musical Instruments
Show More
Show Less
Ask Your Own Electronic Musical Instruments Question
Answered in 24 minutes by:
1/28/2016
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago
Rusty
Rusty, Music Professional
Category: Electronic Musical Instruments
Satisfied Customers: 5,929
Experience: Sound Engineer, Electrical Issues, Tone Consulting
Verified

Hello, my name is Rusty. Here is the block diagram of the piano:

Keys --> Tone Generator --> Pitch Bender --> Amp circuits

You said something about the "audio board", which I/O connectors are problematic? Are you able to play the piano with the I/O circuits disconnected?

Ask Your Own Electronic Musical Instruments Question
Customer reply replied 1 year ago
Hi Rusty,
There are AC power, DC power, Sliders, Phones, Left and Right Tweeters, Left and Right Woofers, and Audio I/O connectors on the audio board. Obviously if the AC or DC power is pulled you get nothing. By nothing I mean no popping and no piano sounds. When I pull the Sliders connector (Bass, Treble, Main Volume) it breaks the circuit to the audio amp section and I get nothing. The headphone jacks appear to be break jacks that allows quiet practice by disconnecting the audio feed to the amplifier/speakers. If I pull the Phones connector on the audio board, I get nothing. Now I am not sure about the I/O connector to the back panel. Thinking back, I don't think this connector had any effect on the speaker output or headphone output, since it is for external inputs and midi I/O.
I disconnected the speaker connectors and just used my headphones to verify that the piano sounds were being generated. They were, but the popping was much louder. But the tone generator/pitch bender all appears to be working OK.
I suppose it is possible for something to be loading down (breaking down?) to cause the power supply rail to either go to ground or momentarily spike to a higher voltage, causing the amps to pop. I could put the O-scope on the various IC pins to look for the pop, but without a schematic, I would be truly shotgunning. I like to take a more systematic approach to trouble shooting, but don't know where to start on this animal.
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago

Yes, and the problem is usually in the pitch bender circuitry. If a capacitor starts to leak, it will start to pop. I want you to disconnect the output of your pitch bender just before the amp circuits, and test for DCV on the output. If you see spikes indicating the pops, reconnect the amp, and disconnect the pitch bender from the tone generator. Look for those same spikes. This will tell us if the input to the pitch bender is clean, to determine whether it's coming from the tone generator or the pitch bender.

In my experience, it's usually in the pitch bender circuit.

Ask Your Own Electronic Musical Instruments Question
Customer reply replied 1 year ago
Sorry for the slow reply. The piano is still in the customers home. I may be able to get back into it tomorrow. Is the tone generator and pitch bender under the shield, I assume with the processor?
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago

The tone generator is connected to the motherboard, power supply, and pitch bender. The pitch bender is connected to the tone generator, power supply, and amp circuits. It's the smallest board in there, with all of the resistors, and it's connected to the pitch wheel. The processor is on the motherboard.

We need to check at the pitch bender input and output for spikes.

Ask Your Own Electronic Musical Instruments Question
Customer reply replied 1 year ago
Rusty, I hope to get back into the customer's home tomorrow and dig back into this piano. I may need your further expertise after getting back into it. That is why I have not yet rated your help. So, please be patient with me. Thanks, Terry
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago

I'll be in and out today. I have to stock up on audio gear for the year, but I'll check in periodically. Run the tests I suggested, and use the process of elimination to locate the pop.

Ask Your Own Electronic Musical Instruments Question
Customer reply replied 1 year ago
Rusty,
I did extensive testing today. Found the pitch bender board and disconnected the flat cable and the cable going to the amp board. The popping continued. Also noticed intermittent 100KHz oscillation at the left tweeter output. All DC supply lines looked clean. Fed in an external test tone through the back and all amplifiers/speakers reproduced the tones cleanly with no popping. But when I tried to play the keys, the popping began again. Not sure if this piano has an actual bender wheel, unless it is under a protective cover. Regardless, I was able to trace the keys tone input signal onto the amp board. It did feed the right power amplifiers (both treble and bass), but it never made it to the left power amplifiers. Tried to isolate the actual preamp IC that the signal was being lost, but it appears the first IC has a combined external and internal signal present. Do the get mixed in the FETs ahead of the first IC? The IC's appear duals set up for left and right audio. After going through the first preamp IC, only the keys audio for the right side was getting passed on. It appears I am lossing the keys audio in the preamp stage and for some reason is causing an intermittent pop that drives it into oscillation. Sure wish I had a schematic. Sorry, but it was not the pitch bender.
Customer reply replied 1 year ago
Sorry, I meant to send pictures of the interior and the left side of the keyboard where the pitch wheel should be.
IMG_1487.JPGIMG_1487.JPGIMG_1488.JPGIMG_1488.JPGIMG_1489.JPGIMG_1489.JPGIMG_1491.JPGIMG_1491.JPGIMG_1492.JPGIMG_1492.JPGIMG_1490.JPGIMG_1490.JPG
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago

No, the bender wheel would be in plain sight. I like what you've done here, and now we have it isolated to the tone generator. That's not a good thing.

Does the popping remain consistent on each key? How about does it make a difference how much popping occurs by how hard you hit the keys? I'm checking to see if it's a blown capacitor in your tone generator. Since you could insert tone without the popping, that tone also goes through your pitch bender, so the problem is now isolated to the tone generator.

Ask Your Own Electronic Musical Instruments Question
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago

I like what you said about the preamp stage as well... Check for spikes, the tone generator is quite a bit more to troubleshoot than the pitch bender.

Ask Your Own Electronic Musical Instruments Question
Customer reply replied 1 year ago
I connected the scope probe to the audio input from the volume control on the Sliders connector on the audio board. It appeared to be mono at that point. It did go up and down with the volume control and appeared to be clean regardless of the particular key or how hard it was struck. When I looked for the audio leaving the amplifier board going tot he headphone jacks, I saw the audio for the right side leaving on the Phones connector and returning from the headphone jacks. However, there was no sound leaving the board for the left channel nor returning from the jacks, for the keys. When using the external input, I saw clean audio leaving for both left and right and returning from the headphone jacks.
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago

Disconnect the tone generator from the pitch bender. Check just the output of the tone generator. That should generate the spikes. With the lack of a service manual, you'll have to trace it back.

Ask Your Own Electronic Musical Instruments Question
Customer reply replied 1 year ago
Rusty, after thinking about how I left the piano on my last visit, I am confused about the tone generator. Does it generate a stereo (left/right) output or is the tones mono going to the bender and then to the amplifier board? I left one woofer speaker connected to one side only and the piano plays clean (no pops) even with the master volume set to max. If the tone generator was causing the spikes, would they not be on this one amplifier/speaker? There must be a mixer on the audio amplifier board that combines the external input with the tone generator. That area of the audio board has a great deal of discrete transistors or FETs, so they are difficult to troubleshoot without being able to follow the board traces. Is it still possible that the mixer area is the place where my tones are being cut off and the popping is taking place. I also noticed that there is active filter sections to separate the treble for the tweeter amps from the bass feeding the woofer amps.
Electronic Musical Instrument Expert: Rusty, Music Professional replied 1 year ago

On that particular model, do you have two or three signal wires coming from the tone generator to the pitch bender? I believe it sends a stereo sound, but I could be wrong on the Kurzweil.

What about when you reconnect that speaker, and disconnect the other one? Does it play clean?

Ask Your Own Electronic Musical Instruments Question
Ask Rusty Your Own Question
Rusty
Rusty
Rusty, Music Professional
Category: Electronic Musical Instruments
Satisfied Customers: 5,929
5,929 Satisfied Customers
Experience: Sound Engineer, Electrical Issues, Tone Consulting

Rusty is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

jaimzness

jaimzness

Engineer

117 satisfied customers

DAW and MIDI techniques. Keyboard and synthesizer programming. Electronic repair.

stereoaz

stereoaz

Technician

27 satisfied customers

20 years repairing electronic musical instruments,amplifiers,speakers.

Tyler, M.M., CAGO

Tyler, M.M., CAGO

Professional Musician

312 satisfied customers

20 years training & experience. Familiar with a variety of instruments.

Steve G.

Steve G.

Engineer

83 satisfied customers

I have played electronic keyboards for 40 years.

Daniel

Daniel

Engineer

54 satisfied customers

BSEE (Electrical Engineer), 10+ years electronic design experience ,chip, board, component expert

Musicman

Musicman

Customer Service

52 satisfied customers

I have built and serviced hundreds of electronic musical instruments.

Rod

Rod

Engineer

36 satisfied customers

Engineer - Electronic equipment repair

< Previous | Next >

Related Electronic Musical Instruments Questions
Is there a way to transpose the pitch of the keys up or down
is there a way to transpose the pitch of the keys up or down on a model PSR E243 YPT-240. If not, is there a model that will allow this function? … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
How can I use my PR40 microphone with my Icom ic-756pro2. 2
How can I use my PR40 microphone with my Icom ic-756pro2 … read more
Harry
Harry
493 satisfied customers
I have a Model T-524A Hammond spinet organ -bought in
I have a Model T-524A Hammond spinet organ -bought in December 1974. Several years ago I had a Hammond technician work on it because of a loud humming noise emitted every time I turned it on. But just… read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
I moved it from one room to another (about 25feet) and
I moved it from one room to another (about 25feet) and plugged it in and have zero response. It's a Roland KR-650. Oh- it worked fine before I moved it … read more
Richard
Richard
IT Manager
IT Manager, Consultant
3,273 satisfied customers
I have a Yamaha MOXF8 and it powered itself down due to time
I have a Yamaha MOXF8 and it powered itself down due to time and now it won't exit the setup program. I don't know what to do :( … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
The record / play back options do not work. Neither can I
the record / play back options do not work. Neither can I get the prerecorded music to play … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
I have been writing compositions for the church I attend on
I have been writing compositions for the church I attend on the island of Kauai, the West Kauai United Methodist Church. One of our church members who recently moved back to the mainland had a Sibeliu… read more
Russell H.
Russell H.
computer technology consultant
Vocational, Technical or Trade Scho
780 satisfied customers
I use a GR1 guitar synthesizer with a GK2 pickup. Al of the
I use a GR1 guitar synthesizer with a GK2 pickup. Al of the synth sounds are fine but recently the pure guitar pass through sounds weak and fuzzy. Any thoughts on what it could be, or is there a Rolan… read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
Technics SX-PR53 piano. Sustain pedal will sporadically stop
Technics SX-PR53 piano. Sustain pedal will sporadically stop working. Have checked connection and it is tight How can I repair it? … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
I am looking for help about a particular microphone that I
Hello I am looking for help about a particular microphone that I just purchased. A PCC 160. I can't seem to get it to work and am wondering why? Does any one have any knowledge about these?… read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
I have a Kurzwiel 10 Ensemble Grand. I'm having an issue
I have a Kurzwiel Mark 10 Ensemble Grand. I'm having an issue with the damper pedal. Need some advice on how to order the pedal unit, or ??? … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
After a move my Yamaha Clavinova lost its memory. Can it be
After a move my Yamaha Clavinova lost its memory. Can it be rebooted or what else would you suggest. … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
Unable to pick up fast broadband internet, therefore can I
Unable to pick up fast broadband internet, therefore can I download piano soft audio to my iPad and then using a USB cord directly to the disclavia iv piano ? thank you … read more
Pete
Pete
Engineer
Bachelor\u0027s Degree
1,123 satisfied customers
I have a CLP-810S and I need to replace the lower felt. Do
I have a CLP-810S and I need to replace the lower felt. Do you sell them? … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
No keyboard sound, this is not the first time it has
No keyboard sound , this is not the first time it has happened. It is a Young Chang Co and I thing it is a Kerzweil … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
I have a Roland AT90S Atelier about 16 years old. For years
Hello I have a Roland AT90S Atelier about 16 years old. For years I have had trouble with a few of the foot pedals stop sounding. I have taken and swapped the rubber contact domes from the higher note… read more
Pete
Pete
Engineer
Bachelor\u0027s Degree
1,123 satisfied customers
It's a Roland E-36. The adapter when disturbed cuts off the
It's a Roland E-36. The adapter when disturbed cuts off the power to the keyboard. This happens intermittently. … read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
Aurora Classic 232172 serialturn on and noises starts and
Aurora Classic 232172 serial(###) ###-####turn on and noises starts and gets worse on playing sounds like a thunder and lightening storm, crackles and snaps and booms. Noise seems to come from the rig… read more
Ron Winston
Ron Winston
Owner / Technician
314 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x