one of keyboard speakers not working.

[valius]

Hi, so we have just purchased a very cheap second hand pdp220 keyboard. it had two keys jamming that I managed to fix. Unfortunately found another problem, one of speakers wasn't working. I have checked the speaker with voltmeter and it had good resistance, and it does have a cracking sound when power is on, but sound only comes out of one of them. Would there be a mono setting on keyboard itself ?
Just thought I would ask before dismantling it further.
Or any suggestions on fix would be appreciated.

 

[delaware dave]

If one speaker is out swap speakers. if the bad speaker now moves to the other side then it is the speaker. If the good speaker when swapped doesn't play then it is either an output transistor or the op amp itself. Those parts are not that expensive; if you are handy with a soldering iron it's not too bad a job to attempt on your own.

 

[Biggles]

You can also plug in a set of headphones.

 

[valius]

Actually just tried that, and it only plays through one side of headphones too..

 

[valius]

If one speaker is out swap speakers. if the bad speaker now moves to the other side then it is the speaker. If the good speaker when swapped doesn't play then it is either an output transistor or the op amp itself. Those parts are not that expensive; if you are handy with a soldering iron it's not too bad a job to attempt on your own.

So i did swap speakers and only the one to right side worked...tired connecting headphones and sound only came out of left side....will attempt to disassemble while thing again and see if I can figure it out....check the transistor and amp.

 

[happyrat1]

Check for bulging or leaking electrolytic caps.

Cheap Chinese caps are the bane of every piece of electronics that they ship out.

Visual inspection will only tell you so much though.

A $50 ESR meter will give you a straight answer.

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Gary

 

[MusicwithHarry]

This keyboard looks exactly like something that Alesis also has/had available. I believe it was the Alesis Cadenza.

Depending on how the speaker system is set up, there are different connectors on the PCB that a small plug would plug into for each speaker in the amplifier section on the PCB. It could be that the power amp section could be faulty - sometimes they power the headphone jack(s) as well.

I would also do what Gary has suggested about looking for bulging caps.

Grace,
Harry