Replacing the Battery on a Yamaha DX-7

Current email address for Matt Siegler:
(correct at 13 Dec 1999)

From: (Matthew A Siegler)
Date: Thu, 9 Sep 1993 22:32:48 GMT



(B.S. begins here)

*************************** DISCLAIMER ****************************
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*************************** YOU HAVE BEEN WARNED ****************************

*************************** WAIVER OF COPYRIGHT ****************************

This document may be copied freely without notice or permission of the author.
In fact, it is encouraged. However, if the semantic content is modified in any
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These instructions were written for the individual with general technical
experience, by someone with general writing experience. At times you will
feel treated like an idiot. Any advice regarding the revision of this
document is encouraged, and should be forwarded to: or
(Matthew A. Siegler) (Matthew A. Siegler)

What is This?
All Yamaha DX7 and DX7s models come with a lithium battery used to keep the
internal memory alive when the power is off. This battery can last anywhere
from three to six years, depending on how much the machine is on during that
time. At the end of its life, it is mandatory to replace the battery, as it
can decompose and leak acids onto the expensive motherboard.

The BATTERY VOLTAGE function indicates the state of this battery. It is
common for this function to be dead wrong in evaluating the voltage. An
indication of a battery near the end of its life is a sudden voltage drop of
10 to 20 percent. A better indication is erratic memory function when the
machine is turned off. When in doubt, it can't hurt to put in a new battery.

What You Need to Have

A Yamaha DX7 or DX7 keyboard without E! installed.
E! requires extra procedures, which I do not know. However, if you
installed it in the first place, it shouldn't be hard to uninstall it.

A new battery from Yamaha.
Unfortunately, you cannot pop down to the drug store and pick up a
Panasonic CR2032 battery and just stick it in. The Yamaha battery has
special wires spot welded to it. If you are really mechanically inclined,
you may be able to kludge this.

A good #2 phillips screwdriver.
If your keyboard has never been opened, you will need a decent screwdriver.
The folks at Yamaha tightened the chassis screws REAL tight on some units.

A 15-40 Watt soldering iron.
Please do not use anything larger than 40 Watts, you WILL fry the board.

Someplace to stick the MANY screws you will remove.
Although almost every screw is the same, losing any of them compromises
the outstanding mechanical integrity of the machine.

What You Need to Know
Beyond proper use of basic tools, the only special skill required is soldering.
If you can't solder, you can probably find someone else who you trust to do it.
In fact, only two wires (the battery) need to be desoldered, and resoldered.

Getting Started
Store all your sounds somewhere external, they will probably be lost.

Unplug the keyboard, and remove any cables or cartridges plugged in.

Put the keyboard on a flat surface at least twice as deep as the chassis.

Opening it up
This keyboard is a real pleasure to work on, being easy to service.

1. Remove the four screws from the underside of the keyboard that do not hold
the rubber feet down.

2. Remove the four screws at the corners of the control panel.

3. Remove the small screw to the right of the power switch on the back panel.

4. The front panel hinges up like a foot locker. Lift it until it stops at
its back-most position.

The panel should stay there and not swing down. If you are concerned about
this, prop it up with a nonmetal device. Looking inside, you will see the
battery in the center of the motherboard.

Pulling Things Out
With a little care, you can start yanking this thing apart. Make sure
that you never use any force on any part. If you need to, you are doing
something wrong!

1. Remove the two screws above the pitch and modulation wheels.

2. Remove the screw at the far right of the keyboard, above the final key.

3. Remove the screw and locknut holding the THICK GREEN grounding wire to the
metal cabinet. The screw is about 3cm up from the screw removed in (2).

The keys are now ungrounded from the rest of the machine. Try to avoid
static discharge at this point or you will screw something up.

Now you are ready to start messing with cables and stuff. Remember to be
gentle. Insight will win over brute force on ALL of the connectors in here.
Some of them will seem impossible to pull apart because they never have.

4. At the left end of the keyboard, at the top of the panel with the mod and
pitch wheels, there should be three sets of wires running under the
panel. Two of them will be bundled together tightly with a thick black
insulated piece of metal, sort of a industrial strength twist-tie. The
other bundle is loose.

The two bundled together are the feeds to the mod and pitch wheels.
You must disconnect them at the black boxy connectors. Look closely at
the connectors. One side is flat, the other has a lever thingy on it.

                         ======* lever thingy
                     ___/_  ||
SIDE VIEW     ======|     |_||___
                    |     |      |-----

                 ------|     |______
TOP      from    ======|     |      |===== to panel
       motherbd  ------|     |______|=====

Hold the smaller end of the box in your right hand, with your thumb on the
flat side, your first finger on the lever thingy, press the lever thingy
down, and pull the box apart. It should come apart, REAL EASY, like buttah.

5. Repeat this for the other box. They are different sizes, so you cannot
forget which plugs into which.

6. Now for a tricky step. Locate the massive ribbon cable at the right
end of the motherboard. There are probably some felt tip marker
lines written on it. You need to pull this out at the motherboard end.
Carefully rock this end of the connector back and forth until it comes out.

7. With your right hand hold the keyboard at the last octave, wrapping your
fingers underneath them. Pull the keyboard back toward you, in the
opposite way that the control panel angled back. Pull it to about
45 degrees and hold it there!

8. With your left hand, reach under and pull out the WHITE multi pin
connector with the yellow and brown wires connected to the mother board.
It should come off REAL EASY.

9. Now you can take off the keyboard panel completely without fear.

The Mother of All Boards
Exercise caution when working here, you can break something if you let your
screwdriver go wild.

1. Remove the screws on the big metal bracket in the center of the case.
Pull out the bracket.

2. Pull out every connector on the mother board. The positions will
stay pretty much where they came from, so you wont have to worry about
which is which later. Many of the connectors are of different sizes also.
3. Remove the seven (?) screws around the perimeter of the board.

4. If all has gone well, you can now pull out the motherboard.

New Battery
The battery is solder into the board as in the following diagram:

               POSITIVE SIDE            ==========
                     __________________|____     |
                    |                      |     |
                    |                      |     |
                    \______________________/     |
                                |                |
               NEGATIVE SIDE    |                |
                                |                |
                               *|*              *|*
                                |                |

You need to remove the battery and install the new one in the same way.
Make sure you use correct polarity. The flat side of the battery is POSITIVE.

When you solder the new battery in, clean any extra flux away. Flux can
create leakage currents which decrease the lifetime of the battery.

Closing Up
Most of the instructions are just the reverse of above.

1. Put the motherboard back in the case, and insert the seven (?) screws.

2. Reattach the metal bracket with its screws.

3. Plug all the connectors back into the motherboard, there might be a socket
with no plug in it. It was there when you started.

4. Close the top without screwing it down. You are going to check to see
how your surgery went. Plug it in and turn it on. If anything funny
happens, turn it off and call a Yamaha rep. Otherwise go ahead and
check the battery voltage. It should be normal now.

5. Turn it back off, unplug it, and open it up again.

6. Put the keyboard back where it came from, and attach the WHITE
connector that you had to remove to get the thing off.

7. Reattach the ribbon cable, and the mod and pitch wheel connectors.

8. Attach the THICK GREEN grounding wire to the base.

9. Insert the three screws that held the keyboard down.

10. Close the control panel.

11. Insert the four screws on the face, and the small one by the switch.

12. Insert the screws on the bottom.

You are done. Good luck, and feel free to send email for additional info.