Replacing the EPROMs in an Ensoniq VFX series synthesizer
These instructions were written based on the SD-1, but the process is
nearly identical for the VFX and VFX-SD.
First, remove the four allen screws holding the top cover on and open
the synthesizer. There are a bunch of ribbon cables packed in there,
so it's difficult to see the EPROMs straight away.
Figure 1. A wide view of the inside of the Ensoniq SD-1, showing a mess of
The OS EPROM chips both carry white stickers that indicate which OS
version they have "burned" into them. In order to see the OS EPROMs,
one must remove the ribbon cable that connects to the main board and
runs to the keyboard.
Figure 2. A closer view of the ribbon cables, with the ribbon for the
keyboard in the center.
Figure 3. With the keyboard ribbon cable removed, one can see the OS
EPROM chips. Note the white stickers on the chips.
Using a good IC-puller tool, grip one of the EPROMs tightly. With care,
pull upward to remove the EPROM. The chip may need a bit of wiggling
from side-to-side in order to get it free from the socket, but be
careful not to wriggle too forcefully and bend the pins.
Figure 4. Gripping an EPROM with an IC-puller tool.
Repeat the process for the other EPROM chip.
When the EPROM chips are free, replace them with the EPROMs that have
the desired OS version. When inserting the EPROM chips into the
sockets, be careful that the pins align with the socket holes well, or
the pins may bend as they are pushed into the socket.
OS version 4.10 is the last release from Ensoniq.