Kurzweil Mark Pro One stopped working

[pattyjh]

We got the piano a number of years ago and have loved it.  About a month and a half ago it stopped working for a day and then it was back.  Now it has stopped working and hasn't come back.  My husband has changed a small CR2032 battery that he found (the old one was dead - he tested it)  It still doesn't work.  Any other suggestions?

I did talk to a piano repair replace.  They won't have anyone in till next Tuesday and there are 8 pianos ahead of us.  We would really like to just repair it ourselves now if we can. 

[timothy42b]

What are the symptoms?

[pattyjh]

It was working fine.  Then the next time we turned it on it didn't turn on.

[pattyjh]

OK, just asked further info from DH.

I thought it was just dead. But I just asked DH and there was quite a bit more.  He is writing it up now and will email it to me and I will post again.

[pattyjh]

OK DH says:

When you press the power button, the function light blinks several times as it goes through it's diagnostics.  Then you can hear the relays click.  Then, when the piano was working you would hear a hum, then when you pressed a key, you would hear the note.

Now, we don't hear the hum and when the key is pressed, there is no note.

The control buttons all seem to behave normally, lighting up and going out the way they always did depending on what sequence you press them in.

-----

My suspicion is that the power output stage that drives the speakers has a problem.  What I really suspect is that the electrolytic capacitors have gone bad.  That can happen and might explain why for a while, the piano would turn on just fine one day, but a few minutes later wouldn't, then a few minutes after that would turn on just fine again.

[indianajo]

Yeah, at 15-20 years of age electrolytic capacitors are a a bit of a sure shot be going bad.
They are also one of the few parts that can be replaced - unless they get so bad they short out the power rectifier (cheap) or power transformer (expensive and usually impossible to find).  So change e-caps now.  
The ones nearest the power transformer are the ones most likely to go first, they get the hottest.  
Get on organforum.com and read the safety sticky thread, you need to follow those procedures to avoid hurting/killing yourself when repairing electronics.  
See post 2 of this thread https://www.organforum.com/forums/showthread.php?22234-Could-anyone-please-help-me-out-with-a-Thomas-Trianon&p=280146#post280146
Organs, "pianos", hifis, all about the same problems. E caps, contacts, connectors, mostly, occasionally 78xx regulators or 39xx or 29xx op amps.  
The only reason I'm responding it is vaguely possible an old Kurzweil was made in USA.  
If it is some oriental ***** of ****,  throw it away and buy a wood piano. Say a pre-globalization Baldwin, Hamilton, Sohmer, Wurlitzer, Mason & Hamlin, chickering.  See the thread about "the best upright piano" for my post on how to find and test for a superior $200 piano, be it 20 or 120 years old. https://www.pianostreet.com/smf/index.php?topic=56680.0 
I'm this week tuning an 80's Wurlitzer that sounds so bad it has been relegated by the church to a plant stand, with water damage etc. It sounds like ****, one note is 4 tones flat and most are a half tone or moe.  But won't sound bad when I am done, I'm pretty sure,  Middle C is sounding nice.   And it is fast enough for 99% of players in my town, although my 1941 Steinway 40 is a little faster.  This wurlitzer has a bass only middle pedal, which is good for some middling advanced repretoire if one can't afford moving in a grand. (I can't). 
Good luck.