SX-PR602, 702, 902, 603, 703, 903, 1000, 604, 804 amplifier boards

 
Read all of this before you start.

Read the sections of my Technics page
“If opening piano to remove circuit boards” and
“Tips for removing circuit boards” and also
“Packing” and “Shipping method”

For your own safety, unplug the piano before opening it

Make drawings or take photos and make good notes so you can refit everything correctly.

NOTE: my description assumes you are standing in front of the piano

1 – make sure the piano really is unplugged from the mains!

2 – take the top off the piano (not the PR1000 which is different)
Don’t try to remove the back of the piano
Four screws on back of piano in a row near the top, then knock top forwards, then lift off
Slide keyboard cover shut over the keys so you can see inside the piano

3 – do drawings or take photos and make notes of where connectors go

4 – unplug five connectors – see description below

5 – remove screws – see description below

6 – get the board off its nine mounting posts – see description below

Again, my description assumes you are standing in front of the piano

One small connector in front left-hand corner  
Unplug by firmly holding and pulling gently upwards the bunch of wires which come up out of the top of the connector.

One connector about halfway along the right edge of the board

All models except PR604 and PR804.  This connector will not unplug from the amplifier board so do not try.  It has to be unplugged from the main board (the green one) which is immediately to the right of the amplifier board.

Note for PR602 only.  There is a screening card over the main board.  You have to bend up the left-hand edge of the screening card to see this connector.

Look at the connector where it is plugged into the main board (the green board).  Part of this white connector is a small white tab.  This is on its right edge and sticks out to the right.  Put your finger under the tab and ping it upwards.  If it doesn’t unplug at the first attempt, try again.  Don’t try using anything except your finger or you could damage the board.  When you have unplugged the connector, plug it back in again by pushing it down firmly several times with your thumb.  You should be able to see that it is lined up properly before you plug it back in.  Unplug and reconnect it a few times until you are familiar with it.  This will help when you are refitting the board.

PR604, PR804 only – the connector has wires coming out of the top and can be unplugged but will be harder to unplug than the previous one.  Connectors with more wires are harder to unplug.  Don’t jerk the wires upwards.  Use what I call controlled force.  Try to avoid one end of a connector becoming unplugged suddenly as this can bend the terminal pins at the other end.  If this happens, don’t try to straighten the pins.  I will do this.

One connector midway along rear edge of board – comes from the transformer  
You can’t just pull up this connector to unplug it because it has a built-in latch on its rear face.  Hold the front and rear faces of this connector near the top between thumb and finger.  Squeeze firmly which should open the latch and then the connector can be unplugged.  If it won’t unplug, you haven’t squeezed the top of the latch enough.

Two connectors on left edge of board  
The latch is on the left face of these and they unplug in the same way as the previous connector.

NOTE – When you reconnect any of these, make sure they are lined up properly.  It should not be possible to plug them in wrongly (e.g. one step sideways) but do be careful !

One or two black earth (ground) wires (depending on which model piano you have)
These are soldered to the board and screwed down to the main shelf of the piano.  Remove the screws.

The board is mounted on nine nylon posts – three along the rear edge, three along the front edge, one midway along the left edge, one midway along the right edge, one in the centre of the board
Each nylon post has flared-out bits which must be squeezed together using long nose pliers whilst you try to ease the board part-way up the post.
WARNING – DO NOT TRY TO GET THE BOARD COMPLETELY OFF EACH POST
The posts can be a very tight fit and the board is made of paxolin which is quite brittle and will crack if bent too much.
You have to work your way round the posts, easing the board a little way up each one in turn.  Sometimes, very annoyingly, whilst you’re struggling with one post, the board may pop back onto a post you started previously.  As an idea to stop this happening, one customer suggested placing pieces of pencil eraser under each section of the board which has been started up a post.  Some boards are quite easy to remove but some can be very difficult indeed.  

If the board is a really tight fit on the posts, don’t fight it.  Be patient and take your time.  Don’t pull up the board too hard.  If it comes up suddenly it may crack!  It may seem impossible at first but just keep trying – a lttle bit at a time – and you will eventually get the board out.  If you rush or get cross you might damage the board.  I can repair cracked boards but this will make the job more expensive.

I usually ream out the holes a bit to make it easier if the board ever has to come out again.

Packing – use a box big enough that the board is not a tight fit.
IMPORTANT – use a deep box so the board can’t get squashed or crushed in transit.

E&OE