Yamaha keyboard psr 70

I JUST RECEIVED A PSR70 YAMAHA THAT HASNT BEEN USED IN AWHILE. WHEN I TURN IT ON I GET NO SOUND OUT OF THE SPEAKERS. I TRIED PUSHING EVERY BUTTON IMAGINABLE BUT DOES NOT WORK. THE ONLY THING I FOUND IN THE INSTRUCTIONS IS BEFORE PLAYING INSERT 6 D CELL BATTERIES BUT NOT SURE HOW THIS WOULD BE THE CAUSE OF THE SOUND PROBLEM. THERE ARE NO BATTERIES INSIDE THE UNIT. DO YOU THINK THERE IS AN INTERNAL AUDIO SOUND PROBLEM WITH A SOUND CARD?? PLEASE ADVISE IT WOULD BE MUCH APPRECIATED BECAUSE IT APPEARS THIS WILL BE A LOT OF FUN.\\


THANKS DONALEE

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Sep 30, 2014
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YAMAHA PSR-70 Keyboard - Lights On - No Sound
by: G8OTA

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 of kilo-ohms) after years of non-use.. They are re-polarised / reformed when equipment is switched on after a period of non-use and this effect would probably not be noticed since it make only take seconds 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 a 4700 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

henryotani@googlemail.com



Jul 11, 2014
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Chuck it out the window
by: Anonymous

Do yourself a favor and toss the thing in the trash bin, it's a piece of crap. My parents bought me a PSR-70 for my graduation gift in 1986 thinking it was a synthesizer. When I politely told them it wasn't, and that the one they looked at at another music store WAS ("We didn't like that one, it had all these levers you had to move around to make the sound of a clarinet. This one just had a button that said 'CLARINET', so we thought that was better.") and asked them nicely to take it back, they wouldn't.

"We could've bought you your dream gift, but instead we decided to take ten 100 dollar bills and set them on fire."

Oct 29, 2009
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Keyboards on Ebay
by: Alfred

Dear Donalee: In my message I should have emphasized "DEPENDING ON YOUR BUDGET". You should also take into account the fact that you should be looking to replace your PSR 70 WITH AN EQUIVALENT UNIT. The two posts subsequent to mine
are probably for later models with more features.
Do not be discouraged. I'm sure there are keyboards listed which will fit your needs.
Regards.

Oct 29, 2009
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PSR-70 REPLACEMENT
by: KMIELL

here's the item number for one on ebay. 260491942179 only problem is he has a BIN $900 lol opening bid is $300 lol i think this guy has been out of the loop a little too long.

Oct 29, 2009
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psr70 on ebay
by: Anonymous

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260491942179&ssPageName=STRK:MEWAX:IT only problem is this person thinks its worth $900 and bid starts at $300 lol. sned him a message i did. should be more like starting at $30 and bin for $90 maybe.

Oct 26, 2009
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PSR 70
by: Alfred

Dear Donalee: Your description is clear, and there are myriad possible answers. The unit is fairly old (yamaha released it in 1985)and while there is a chance it may be possible to restore it to working condition, the expense would make it unfeasible. The ONLY THING you may want to do is buy an Adaptor (Battery Eliminator)to see if you can plug it in and bring life back. I don't mean to dampen your enthusiasm. As a matter of fact, depending on your budget, you would be far better off buying a used keyboard from Ebay. Just make sure you bid on one which is offered with a guarantee to be in 100% working condition,with an Ownewer's Manual and a return option. Read and understand Ebay descriptions carefully. Good luck.

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