Yamaha DX7mega128 Manual
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Yamaha DX7mega128 Expansion Install
1: Introduction
The DX7mega128 a powerful option board that provides increased memory and greater control of
the DX7.
While the installation is fairly simple, it still requires patience and general electronics
knowledge. We accept no responsibility for the work you perform on your DX7. Read over
the following installation description and if you feel you are not capable of the work
required, turn the project over to a qualified technician
Precautions!
High Voltage Safety Warning
Unplug the audio cable. Turn the DX7 power switch OFF and unplug it from the wall.
Disconnect any other connected cables before opening the DX7.
ESD Precautions and Proper Handling Procedures
You should observe standard static-safe handling behavior when working with sensitive electronic
equipment such as synthesizers:
o Avoid carpets in cool, dry areas.
o Dissipate static electricity before handling any system components by touching a
grounded metal object.
o If possible, use anti-static devices, such as wrist straps and floor mats.
o Take care when installing the board. Prevent damage to the connectors by aligning
connector pins before you apply pressure. A damaged pin can render the board unusable
and can cause damage to system components at power-on.
o If disconnecting a cable, always pull on the cable connector, not on the cable itself.
Tools Required
o Standard Philips screwdriver.
o Standard flat-head screwdriver (small).
Condition of DX7
While the DX7mega128 will replace the functionality of damaged or missing EPROM and/or
SRAM chips, it will not correct other problems your vintage synthesizer may have. It is
recommended that the synth be in otherwise good condition before beginning the installation. For
instance, the battery voltage should be checked and the battery replaced/repaired by a tech if
necessary. Sockets for the EPROM and SRAM chips should be in good working order and not be
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dirty, oxidized, rusted or otherwise compromised. If repair is required, do it before installing
DX7mega128.
2: Installation
Back up your patches if they are important to you!
Open the DX7
Using a Philips head screwdriver, remove the 5 screws from the front panel. Two are located
on the left front. Two are located on the right front. A final one is located on the right rear. Set the
screws aside, noting that the rear panel one is the shortest.
(Re)Move the Keybed & Remove the Keyboard Rail
It can be difficult to see the delicate pins when installing the DX7mega128 board. By moving the
keybed (the chassis with the keys) and removing the silver keyboard rail, you will have better
sight lines and freedom of movement when installing the DX7mega128 board.
.
Remove the 4 large external screws from the underside of the keyboard along the front
edge. The photo below shows the inside front edge of the empty case bottom and illustrates the
location of the 4 screws. You will, of course, be unscrewing from the DX7 underside.
Loosen the 3 internal screws at the extreme right and left ends that hold the keybed in
place. It is not necessary to extract them from the holes they reside in.
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Carefully lift the keybed slightly up and out (toward yourself) an inch or so.. You don't need
to move it much. You will probably need to free up one or more cables to accomplish it. Or if you
prefer, disconnect the cables and completely remove the keybed.
This will give you access to the 3 screws holding the silver keyboard rail in place. Remove those
three screws and set aside the silver keyboard rail. (Shown here with keybed removed).
You now have excellent
access to the DX7 main
board. If you do remove the
keybed you may find it easier
to remove the small yellow
cable and large flat grayish
cable at the main-board-end
rather than from the keybed.
You will also need to unclip
two small cables on the left
end (mod wheel and pitch
bend). There may also be
wire tires and/or cable
fasteners to deal with.
Remove the EPROM and SRAM ICs
The next step is to remove the EPROM and two SRAM ICs.
The EPROM is found in location IC14 and the two M5M5118P SRAM chips (or similar) are
located at IC21 and IC20.
Remove them by prying slowly at each end of the chip back-and-forth with a small flat-head
screwdriver. Avoid touching any of the metal pins with the screwdriver.
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Place them safely aside on anti-static foam. You can use the reverse side of the foam shipped
with the DX7mega128.
The photo above shows the 3 chips removed.
After removing the chips, also remove the screw shown at the
center of these photos near IC23.
Install the DX7mega128 Printed Circuit Board
Hand tighten the supplied nylon standoff into the screw position near IC23. Tighten it well by
hand, but there is generally no need to use a tool. Do not over tighten or strip the threads.
Remove the DX7mega128 board from the anti-static foam. Inspect the bottom of the board to
make sure none of the pins have been damaged. You should see one collection of 28 pins (2
parallel strips of 14 pins), one strip of 12 pins and a strip of 8 pins.
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Place the DX7mega128 board gently on the DX7 main board so that the 28 pins that form a DIP
package align with the vacated IC14 spot. The 8 pins along the edge should align with IC20. Do
not press the board in place yet. You can use a small mirror to check the pin alignment.
Once you are happy that all the pins are aligning with the desired locations, firmly and evenly
press the DX7mega128 board in place. Make a visual check to see that the board is flush with the
sockets.
Using a screwdriver, carefully tighten the original main board screw through the DX7mega128
board into the nylon standoff. Again do not force it or over tighten as this can not only strip
the standoff, but it can cause the DX7mega128 board to change position. It should be tight
enough so that it cannot work lose. Double check the pins.
Reassembly
Remove all tools from the DX7. Carefully reassemble the DX7 in the reverse order, taking care to
replace the correct screws in the various locations. If you disconnected the green keybed ground
strap wire don't forget to screw it back in.
Test
Plug the AC cable in and turn it on. After a few moments, you should get a greeting message like:
* Welcome to *
* DX7mega128 *
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You can do a quick version check of the board by pressing and holding the brown FUNCTION
button and also pressing and holding buttons 16 and 32. You should see something like the
following:
DX7mega128
Version 1.20
Press the green INTERNAL button twice.
Initialization
Since technically the battery has been removed, you may find some of the standard DX7 function
settings have been scrambled. Follow the steps below to put the DX7 into a known good state
before loading your patches back in.
1. Press MEMORY PROTECT / INTERNAL then OFF.
Internal memory protect is now off.
2. Press FUNCTION and then button 13 or button 12 repeatedly until you see FUNCTION
CONTROL Func/Patch. Press NO to set this value to OFF.
There is now one global set of function parameters for the DX7 (later you will see
how to change this so that each patch can have its own function parameters).
3. Press button 13 or 12 again until you see FUNCTION CONTROL Func Data INIT? Press
YES to set the function parameters to the default state.
4. Press button 13 or 12 again until you see FUNCTION CONTROL Volume= and make sure
this level is turned up using the DATA ENTRY slider or YES button.
Check/set the standard DX7 Function settings versus your preferences. You should be able to
load some patches now, but it is still possible that some setting prevents the sound from being
heard.
The patch data memory will certainly be garbled. Use the standard DX7 panel operations to load
the current data bank with your patches. The “Yamaha DX7mega128 Expansion User Guide”
will explain how to select memory banks as well as how to use the other features of this
expansion.
Enjoy your updated DX7!
See the MTG web site for more great vintage synth and drum machine goodies.
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