Omega 8 upgrade tutorial
by
Luca Pilla
The new upgrade for every Omega 8 is
great: it solves some hardware bugs, like randomized voice stealing,
and adds more features like faster envelopes and increased Moog filter
level. You can let Studio Electronics make the upgrade for you (and
they will
tune it also!), but you can also order a kit to do it yourself. The
upgrade is not very difficult, but you need the right tools and some
skills in electronics. Disclaimer: I'm not responsible by any means for
any damage occurring to your Omega 8 from the use of this tutorial.
REMOVE THE POWER CHORD
WHEN YOU ARE WORKING ON THIS FIX, ALWAYS!!!!
Start with the right tools
You will need a soldering iron (1), a solder sucker to remove mold
tin (2), a diagonal cutter to cut the leads from resistors, a PLCC IC
extractor (4), a Philips screwdriver (5) and small pliers (6)
Step #1: disassembling your Omega 8
Remove the nine screws from the upper panel (red arrows). Don't remove
the two central screws!!
Now remove the three screws from the front panel.
On the rear, remove the nuts (red arrow) for every single voice board.
Be sure not to remove the Master Outs nuts. In some Omegas, with
less than 8 voices, you will find three more screws, remove these also
if you want to install the 8th voice card (yellow arrow)
Now remove the upper panel.
You will see the voice boards and the main CPU board, with a bar that
fixes
them to the chassis. Remove the right screw
And the left nut to free the bar
Now, gently take off the bar from the CPU board side, after removing
the three spacers. To make it easier, move the voice boards
towards the front panel and move them also upwards, so that the bar is
free
from
CPU board.
Please note that there is an
alternative method. Listen to Greg words: "I install and remove it from
the left hand side. Once
I install the standoff on the right hand side, it stays there. To remove the bar from
the left, you loosen the two small spacers in between the CPU and bring them together and
tighten them .10 to the left of the CPU. Once they are tightened together they are used to
loosen the bar from the right hand standoff. Once the bar is loosened from the right side,
remove the two small spacers and slide the bar out."
Every voice board has got three connectors you have to disconnect. The
first
is on the upper side of the board
The second and the third are on the lower side of the board. Start with
the
ribbon and then with the power connector
Now extract the single voice board you are going to fix.
Step #2: preparing the voice board
You have to make four mods to your Omega voice boards. In this pic you
can see a beautiful voice board with the big MOTM filter (CS80) on the
left, near the audio output, and the standard MINI/SEM filter board on
the right. You have to replace two caps (1 and 2), the microcontroller
(3), and a resistor to increase the Mini output level (4, under the
MINI/SEM
board).
We have to remove the MINI/SEM board. Cut the silicon joint you can
find on
the connector, with a cutter
Reverse the card and take a look at the two spacers
With small pliers gently move down the two spacers.
Now the voice board is ready for the mods.
Step #3: change the caps and microcontroller
With the iron solder and the sucker, swap the two caps, C90 and C89,
with the new 224 caps.
Now with the IC extractor remove the original microcontroller (the one
labeled with
green star on it) and insert the new one (red star)
Step #4: replacing the resistors
Before upgrading the R153 resistor, you have to check, on every
single board, if there are any differences in the resistor values. Greg
put a lot of work in tuning your Omega, and one step is to change the
resistor value with an additional resistor, soldered on the top of the
original
one. Look at this pic:
The resistor #1 is the original, the #2 and #3 are two resistors in
parallel for the perfect tuning. Remember which is the voice board
where you find these combinations,
you have to add as well the second resistor on the top of the new one,
to keep the original
tuning, if you want. It's not an error, it's analogue synth! The #4 is
the new
resistor (7.5K) you have to replace. The R153 resistor is here
Step #5: reassembling your Omega 8
You have finished with the fixes. Start to insert all the voice boards
back into their slots, and be sure to assign the right voice number to
each board (near the microcontroller there is a selector to change the
voice number). Insert the bar from the last voice board (e.g. #8), and
insert all spacers between the voice boards. Insert the bar in the
CPU voice board and fix it with the screw and the nut you had removed
before. Insert the audio out nuts. Now pay a lot of attention!!! Insert
the first connector on the upper side of the card, then the power
chord. Now you have to be sure you plug the connector properly. It's
easy
to jump a slot while inserting the plug and fire a card like this
Insert the ribbon plug. Now, before you close your Omega, power it up
and see if everything is fine. If you make a mistake in power
connection, you will see smoke.... not a good signal. If everything is
ok, put the upper panel back in place with all the fixing screws. Now
restart your Omega and run the Accutuning procedure: at start some
voices will be probably very out
of tune, don't care about them. The Accotuning will fix every problem.
Enjoy the new envelopes!
Luca
Credits: many thanks to Steeve
for tech consulting and Enrico Dibennardo for final revision.
