General and additional info about removing the main board from these pianos.
Thinking about the countless times and ages I’ve spent on the phone telling people how to do this, I really should have written it out before. Oh well ….
Read all of this before you start.
Read the two sections of my Technics page
“If opening piano to remove circuit boards” and
“Tips for removing circuit boards” and also
“Packing” and “Shipping method”
Unplug the piano before opening it please – I can’t do repairs for dead customers!
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
PR703, PR903, PR1000 only. Look carefully at two connectors near the front left-hand corner of the main board. It is possible to get these mixed up when replacing the board.
Smoke will definitely come out of the MAIN VOLUME if you mix up these connectors!
They are the same size and each has the same type of grey ribbon cable. One grey ribbon cable is longer than the other and goes to a connector part way up the left edge of the board with VOLUME printed on the board beside it. The shorter grey ribbon cable has a piece of green tape around it and is plugged into the leftmost connector on the front edge of the board with MIC printed on the board beside it.
Most of the connectors (including these) unplug by firmly holding and pulling upwards the bunch of wires which come up out of the top of each connector.
DO NOT try to unplug these connectors except as described.
PR603 has no MIC connector so it should have only the longer grey ribbon cable which goes to the VOLUME connector.
However, making notes and taking photos is still a good idea.
Each of the other connectors is a different size so it’s pretty hard to mix up these.
The rear edge of the board has five connectors on the board itself but only three are used.
Most of the connectors unplug by firmly holding and pulling upwards the bunch of wires which come up out of the top of each connector.
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.
The wires from the floppy disk drive loop through a black P-shaped thing which is screwed down close to the board. Unscrewing the black P-shaped thing makes it easier to unplug this connector. For those of you who like proper technical terms, the black P-shaped thing is an inductor or choke. Whatever you call it, it still gets in the way!
One small connector near the front right-hand corner of the board has its wires coming out of one face of the connector i.e. not out of the top. This is easy to unplug by holding the whole connector body (including its wires) between finger and thumb and pulling upwards.
There is one unusual connector about halfway along the left edge of the board. It is white. On the right side of this connector is a small white tab (part of the connector) sticking 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. Surprisingly, you can actually break a fingernail doing this!
If this board has not been worked on before it will have two black earth (ground) wires. These are soldered to the board near the front edge and are screwed down to the main shelf of the piano. Remove the screws.
Also, if this board has not been worked on before it will have three earth (ground) straps which are silver colour metal. If present, there is one near the rear left-hand corner and two on the right-hand edge of the board. They are soldered to the board and screwed down to the main shelf of the piano. Remove the screws.
To avoid these earth (ground) straps getting broken off in transit I usually make a half-inch thick pad of anti-static bubblewrap and place it under the board before wrapping the whole thing in more anti-static bubblewrap. If the straps do break off I can refit them. Quite frequently I get sent boards with no straps at all, and sometimes earth (ground) wires missing. Presumably these have come adrift and not been replaced during previous repairs. The board will work normally without these and I am not aware of it having caused any problems.
Remove the two screws going through the two rear corners of the board.
Now for the “fun” part … getting the board off its five mounting posts.
Go back to ”Tips for removing circuit boards” for info about this.
Then to “Packing” and “Shipping method” for info about this.
Take care that your long nose pliers don’t skid off a mounting post and damage any circuit tracks on the top side of the main board.
E&OE