The Yamaha DX7IIFD display is a very well made and robust instrument. The display is unlikely to fail as it has a traditional green LED back light and Hitachi controllers. High humidity, tech butchery or bad luck however, could cause the zebra strip internally to fail and cause missing segments.

This guide explains how to change the display in a DX7IIFD, in this case we used an OLED from the Roland JX10 kit that we supply. It looks stunning.

Many thanks to Jonathan Williams for doing all the hard work on his instrument, we had an awesome day modifying and repairing synths.

Software Version

This modification was performed on an instrument with Version 1.9 firmware. To access the firmware version number do the following sequence:

Press and hold [Edit] then press [16] and [32] simultaneously.
Firmware version will show, then soft reset occurs. If 1.6 or higher, will also enter test mode.

Disassembly

The instrument has to be disassembled from the rear, god help anyone who needs the instrument powered whilst finding faults on PCBs! First Remove the main board disconnect all cables.

The flat IDC cables in this instrument are incredibly tight. The best way to loosen them is put a screwdriver in between the cable mounted connector “bump” and the PCB connector, and lever apart carefully without pushing hard and damaging the pins. This is especially true of the floppy disk connector. Same technique is used for the display too.

When removing connectors, they were labelled. Some of them are similar size and it is possible to make a mistake when reassembling. Damage can occur if the cables are fitted in the wrong places.

The Yamaha service manual explains how to remove the display and is excellent. However, it doesn’t explain the pitfalls along the way.

Once PSU is clear, leaving mains connections untouched, remove the keyboard. Take care when removing as the contacts are exposed. Dropping a tool or catching one on a cable can cause damage.

Now that the keybed is out, undo the screws on the back of the display and undo the clip that holds the wiring harness in place.

The display assembly can now be pulled clear. Note that for ease of manufacturing, Yamaha engineers decided to stick the display to the window with extremely strong and resilient double sided foam. This is very difficult to remove.

Display Assembly

Here is a picture of the front of the assembly, note that two cable assemblies are soldered to the PCB.

Below shows a picture of the rear, it has an IDC flat cable connecting display to the PCB. This connector has to be de-soldered.

Window Removal

There are various techniques described in forums that destroy the old display. We decided to apply separation pressure and use a scalpel to gently cut and tease the foam.

We also feared that we could scratch the paintwork on the rear of window as it is very thin. We placed a piece of card against the perspex window to protect it from the scalpel. In the pictures below, we should have used a thinner surgeons scalpel rather than a craft knife. There isn’t much space.

Be wary also of scratching the window inside the viewing area. If any paint is damaged, it can be touched up again with more black paint.

Mounting OLED Module

Once the display window has been removed, the assembly looks like below. Remove the IDC cable and all screws to disassemble. We performed the disassembly on an ESD mat to prevent stray static electricity damaging the electronics.

The picture below shows the assembly disassembled. The next step is to de-solder the old display from it’s connector. We used an electric de-soldering tool because not only is it quick but prevents melting of the connector.

The new OLED display is soldered to the connector on the flat cable using pins 1 to 14. Pins 15 and 16 are not connected. If the cable was damaged during removal, then it is possible to buy new connectors and cable to make a new one. The 14 way IDC cable has to be between 150mm to 160mm long.

The back light wires (white and red in picture) and connector are not used anymore, do not connect to the OLED.

To mount the new OLED display, two 15mm M3 machine screws and 4 x M3 Nylon Washers (or a 5mm plastic spacer gets the display super close) are needed to space it from the assembly so that it is closer to the window. The amount of spacing that we thought was initially needed was between 1.8 and 2.2mm but later experiments found that 5mm got the display almost up against the window.

Reassembly

In this fit up, we experimented with different spacings, we reassembled without the window and took measurements to check everything fitted correctly.

The above picture shows a conservative 2.2mm spacing using 3 nylon washers ensuring that OLED module is spaced away from the panel.

The above picture shows a 5mm nylon spacer, this seemed to give perfect results and closer than the original LCD module, but check that the OLED is not pressing hard against the front panel.

Reassemble the display, metalwork and PCB together, taking care with the cable routing to be exactly the same as before. Check that the correct connections were soldered and reassemble it into the instrument.

Before putting everything back with the window, we reassembled with just a few screws to hold it together. This way we could confirm the spacing and fitment. It is a good idea to confirm lineup between edge of OLED frame and edge of casing and readjust the OELD using it’s fixing screws. Best tool for this is a digital vernier gauge.

Don’t start reassembling and finishing up without checking the alignment of the plastic filter/OLED.

We would recommend that the window is fixed with 1cm square of double sided tape to the front panel closest to keyboard.

The top of window nearest to rear of synth has metal pillars that secure the window in place once installed, so only a small amount of tape is needed at the area nearest the keyboard.

Don’t forget to remove the plastic film on the new OLED before assembling to front panel.

Here is the final result without the window fitted. Testing in all modes demonstrated that the new OLED worked perfectly just as it did on the DX5.

Building up the instrument with the window yielded a good result but it is difficult to get absolute perfect alignment with the frame.

 

OLED Availability

If you want one of the fully tested OLED displays used in this guide and up to the job of fitting it, I am happy to supply one. See my availability page for details. If you need a display fitting to an instrument or any other upgrade shown on this site, Plasma Music in UK offer this service. 

The display used is normally supplied as part of the JX10 or JX8P kits and was specially made to order. It has a very thin construction, small dimensions and a US2011 controller. The SuperJX applications were very tricky due to space requirements, so needed these characteristics.

Looking at forums around the web, I noted that Winstar OLED displays available from well known distributors work with the DX7IIFD too.

See this guide to using our standard 40×2 OLED character module.

 

Copyright © 2020 Super Synth Projects, Guy Wilkinson & Jonathan Williams