My mum gave my son her old keyboard a Yamaha psr 70 it worked ok when last used a cople of years ago but now it all lights up but with no sound also tried with headphones still no sound any suggestions as to where to look would be welcome
YAMAHA PSR-70 Keyboard - Lights On - No Sound
This may be the cause if the unit has not been powered up for a while; switched LEDs come on but fails to produce any sound from either or both channels:
Normally one would suspect faulty headphone switch jack or faulty LA4500 power output chips.
Most electrolytic capacitors can be slightly leaky (tens or hundreds ofkilo-ohms) after years of non-use.. They are re-polarized / reformed when equipment is switched on after aperiod of non-use and this effect would probably not be noticed since it make only takeseconds for all electrolytic capacitors to come up to specification...
In the circuit used for the Yamaha PSR-70(see the Sanyo Applications Notes for the LA4500)there is an 'anti-thump' / slow start capacitor (220uf 16V, aluminium electrolytic 'ripple filter' capacitor) connected between pin 9 and ground (of both LA4500 audio output chips in the PSR-70).Since these hold the chip in a power down condition, they cannot 'reform'from a near rail voltage normally present when the chip is turned on, due to lack of power and thus continually hold the amplifiers in a quiescent power down mode..
To remedy, they need to be disconnected and reformed with a 9Volt battery.After the Chips have powered up, there should then be about 90% of the rail voltage on their PIN 9...
They are not necessarily faulty, they just needs for the equipment to be powered up working for a minute (every year or so).Alternatively a4700 ohm(2m/A) resistor temporarily wired from the (9V) + rail(PIN 1) to PIN 9 of the LA 4500 may do the trick..
This reported fault may be very unusual or fairly common (these keyboards now being almost 30 years old...)
Hope this helps someone out - feedback will be appreciated
September 2014
SOURCE: yamaha psr-gx76
when i checked for a manual for your product it came up as musical keyboard not a computer keyboard so if it's the manaul to the muscial keyboard you want here is the link.
http://www.yamaha.co.jp/manual/english/result.php?div_code=emi
type in psr-gx76 into the search then it will show up in the results as pdf file, this is adobe file and will open with that program and most computers have it installed.
hope this helps.
SOURCE: I need a manual for a Yamaha PSR-225GM keyboard.
Hi,
Here's a link where you can download your manual. Good luck & have fun with it! If this helps you plz rate this as 'fixa'. Thank you kindly.
http://www.usersmanualguide.com/yamaha_audio/electronic_keyboards_(portatone_-_portasound)/psr-225gm
SOURCE: Yamaha PSR-530 keyboard works w/batteries but not w/ cord
similar thing happened to me- the keyboard fell off the stand and the power supply was jerked out. Works with batteries but not with the power supply- i had it examined- the circuit board shorted out at the power jack- will need to replace board which is very costly.
SOURCE: lost my keyboard user manual
You can get the manual on the link below.
http://www.usersmanualguide.com/yamaha_audio/electronic_keyboards_(portatone_-_portasound)/psr-70
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I discovered an unsual fault with one like this.. All the light working and the Rhythm LEDs stepping through, but no sound from speakers orsignals from the RCS (phone) jacks..
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