electronics, repairs, service manuals and datasheets discussion community for the repairs professionals and technicians
FAQSearchMembersGroupsRegisterProfilePM'sLogin/Out
Need to repair a professional stage piano: question...

 
Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Equipment Repairs
View previous topic :: View next topic  
Author Message
1976Pianoman



Joined: 04 Jun 2012
Posts: 2

PostPosted: Mon Jun 04, 2012 7:28 am    Post subject: Need to repair a professional stage piano: question... Reply with quote

Hello,

I am a musician with a broken stage piano (Kurzweil PC88 - keeps reseting itself, possible power related problem). I cannot afford a professional repair at the moment and don't see any reason why I can't repair it myself. I have performed circuit board repairs in the past - switched out capacitors. Is there some standard way to test circuit boards to isolate the problem, or do repairs like this always require a service manual?

There is a small possibility that the problem is the power supply. I have opened it but have no idea how to test it. Is there a way to test this thing? Here is the power supply:

http://www.proaudiosolutions.com/power-supply-for-PC-88-ME1-KME61-Rumour-Kurzweil-p/d52001000.htm?utm_source=googlebase&utm_medium=shoppingengine

I assume I am going to need some sort of testing equipment? Is there an inexpensive means of acquiring this type of equipment?

Thank you.
Back to top
View user's profile Send private message
Pentode



Joined: 30 Oct 2007
Posts: 85
Location: Nr. Manchester (UK)

PostPosted: Wed Jun 06, 2012 11:17 pm    Post subject: Reply with quote

You say it keeps resetting itself and that you think it's in the power supply.

I wonder if it's possible to do a visual check on the components for poor soldered connections, they should like bright and shiny not dull or cracked, one area to look is around power regulator transistors or chips that supplies the logic and digital circuits... presumably with 5 Volts DC.

Does it re-set itself when you are playing or does it do it when you are not playing..... vibration from the speakers for instance 'could' cause the fault to appear, this could suggest the fault is of intermittent nature.

Perhaps saying what actually happens 'may' help throw more light on the fault, i.e. does it go completely dead etc. or does it just lose some functions for example.

Dave
Back to top
View user's profile Send private message
Pentode



Joined: 30 Oct 2007
Posts: 85
Location: Nr. Manchester (UK)

PostPosted: Wed Jun 06, 2012 11:21 pm    Post subject: Reply with quote

I just this minute noted the power supply being an adapter, wouldn't be the socket by any chance? I'd certainly be looking at it's internal connections. Pushing and pulling the jack could certainly put a strain the them.

Dave
Back to top
View user's profile Send private message
1976Pianoman



Joined: 04 Jun 2012
Posts: 2

PostPosted: Wed Jun 06, 2012 11:53 pm    Post subject: Reply with quote

Hi,

It happens both when I am playing and even not when I am playing. It has worsened over time. It used to be sparratic. Now I can't get it to stay on for more than 30 seconds before it resets itself. It's as if I were to rapidly cut the power and power it back on. A quick flash.

The really bizarre thing is that I opened it up to change out a circuit board battery that I was told might be the problem. after I had replaced the battery, I ended up accidentally crushing a very large capacitor that seemed to be on the AC power related end of one of the circuit boards. So I ordered a replacement with the same specs:

http://www.alliedelec.com/search/productdetail.aspx?SKU=70187643

..soldered it in, reassembled the keyboard and everything was great. The problem had disappeared! I thought that maybe by some act of God that the capacitor that I replaced was the problem even before I smashed it. That or possibly more likely, the new battery solved the issue. Why it worked great for two weeks after the repair and now all of a sudden the problem has returned and returned much worse than it ever was before is beyond me. The only thing I can think is that the issue has nothing to do with the things I did when I had it opened up. Maybe something else was clearly failing and for some odd reason, the act of opening up the keyboard and messing around inside of it somehow temporary fixed the issue. Very strange.

I can order a new power adapter. Yet they cost $40. I was wondering if there is some way using a multimeter or another piece of equipment that I can test this power adapter to see if indeed it is the problem.

My other question regarding troubleshooting I guess you answered. I was wondering how a pro would go through this thing step my step to find the issue. So typically it is a visual inspection? I could certainly do that. I think my best bet initially is to focus on the power adapter.
Back to top
View user's profile Send private message
Theunis
Guest





PostPosted: Thu Jun 07, 2012 8:08 am    Post subject: power supply resetting. Reply with quote

Check the voltage across the capacitor you replaced. Sometimes a voltage rating that just, just makes it is used but with say a 10% tolerance it is not so good.

If the top of the capacitor can is hot then it is the capacitor that is leaking excessively as it cannot handle the voltage. If the power supply has an overload protection then the current drawn through a leaky cap could trip it

According to the specs for the cap it is 25 Volt so if you measure 20-25 Volts across the cap rather replace it with a 36 Volt capacitor.
Back to top
Display posts from previous:   
Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Equipment Repairs All times are GMT
Page 1 of 1

 
Jump to:  
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Електроника София - Service Manuals Free Download - Prikachi - Service Diagrams

Free TV Schematics Download - HARDW.net - Pinout Master - Jabse Search - Jabse.InK  - Pulsator

Connector Pinout Forum - Новини - SnimkiOt.com - безплатен DNS - Whois разузнаване - Poblizo.com : пътешествия