Technics SX-PR702M parts and repair

Re: Technics SX-PR702M parts and repair

Hello

Sorry that you are having problems with your 703. There may be a number of causes to your problem and from a remote location it is difficult to tell the best route to get you back working again. So, here is my list of checks I would perform if it were a keyboard I was repairing.

I am assuming you are not an electronics engineer so forgive me if I am either typing to someone who is conversant with electronics circuitry or if you have never taken anything to pieces before.

Since you have line outputs on the back of the piano you can take these outputs into an external amplifier and speaker system. Even if you have a redundant stereo system with an aux input you can use this to amplify the piano. You will probably need mono jack quarter inch connectors to phono plugs. At least at this point you should be able to play the piano normally.

Check the speakers themselves. Best way to do this is to remove the boxes around them (you have to take the piano lid off and the two boxes are then easy to see) and remove the wires connected to them. These can be connected to any other speaker although the easiest way to do it is with any cheap chassis speaker that you can buy in your local electrical shop for a couple of $. Should the sound then become clear you just need some suitable replacements for the existing speakers which a hunt around Ebay will show any number of units that are a suitable size match.

The power amplifier is a class D device which is not exactly user repairable. If it has failed then its not exactly going to be an easy fix. You will need the help of a good local engineer. Sometimes a TV repair engineer might help you but there is no guarantee. Unless you have the appropriate skills with a soldering iron I would stay away from it. As a guide though there are a couple of places to check. There are some circuit protector devices on the power rails that can be checked with a multimeter. The only thing I have to change when repairing these are either the output transistors Q16, 17, 18, 19 and sometimes the driver transistors on the ASub circuit but an engineer would have to look at it to be sure. As the piano is producing output via the headphones then we know that the in incoming power lines or +-20 volts and the switch mode power supply creating the +5 and +3.3 volts is all working.

Let me know how things progress. I am afraid I don't think I have any keys although Admin may well be able to source some for you.

Regards

Dave