Warning first. This documentation was never fully checked by
Brian, use at own risk don't come crying anout broken MX-12's we
did kill one in the process of developing this mod - you have
Apologies for the delay in realising this info everybody
involved in this project are very busy people and Brian never
really got around to checking this work. All I can say to those
who have complained online about how long this should gave taken
is you didn't know Brian :)
Brian Murray the crazy geek behind the MX-12 mod died earlier
in the year in an car/motorcycle accident. RIP Thus this
documentation can never be checked by it's creator and is being
released "as is"
The mod is really only an upgrade from the original MX-10 Luma
mod by Ian Andrews much respect to Ian for the original idea.
Justin Maynard 04/11/2006
MGCJerry's comments are in RED.
Hardware devt and mods
Luma key mod - Ian Andrews
Development of the idea & research
Engineering by Brian Murray
What the modification does
The first modification took several months (including time to
source a replacement board!) but having done a few now, the
modification takes Brian Murray under two hours to carry out and
test. It's a fiddly process that requires cutting tracks,
attaching a new chip and connecting various pins and tracks
around the mixer board to the new chip.
The modification of a Panasonic MX-12 vision mixer is a
delicate operation that requires cutting very fine tracks on
circuit boards. It should not be attempted except by an
experienced electronic engineer who can solder like a god. We
will not be held responsible for damage or breakage to equipment
should you attempt to carry out this modification.
The following items are needed:
of Mixer Board from the Technical Service Manual (browser view)
Schematic of Mixer
Board - high res file for download. 1.1 MB
(right click and choose "download
Remove the "wings" on each side of the mixer - these
slide off. Remove (?) screws on the underside of the mixer.
With the mixer right side up, lift the top part of the mixer
and flip it over (hinging from the left hand side) to open the
mixer and reveal its glorious guts.
Now we can identify several points on the mixer. The left hand
section has two circuit boards facing you. The right hand board
is the CONTROL BOARD .The left hand board is the MIXER BOARD
(note, it has an off centre tab at the bottom edge). The MIXER
BOARD is the one that will be modified.
Let's take a closer look at the Mixer Board. Here's a section
from the schematic of the Mixer Board, from the Technical Service
The Conducter View of Mixer Board (Click for large view).
Same panel, showing the bits we'll be working on closely.
In the Superimpose section note the locations of the
following: IC3, IC4, C22, R57
In the Source Section note the locations of TP1, TP2, TP3, TP4
(The TP (Test Points) supply Y and C signal
source, which replaces the superimpose white effect signal).
TP1 = Y1, TP2 = Y2, TP3 = C1, TP4 = C2
Attach the chip to the piece of protoboard. When the
modification is complete, this can be attached to the corner of
the mixer board so that it rests in the gap between the mixer
board and the control board.
The following diagram shows the points of the chip that we'll
be referring to throughout the modification.
IC4 Pin 12.
This one I need a bit of help with, because my diagram isn't
clear enough. Just what is going on here?
Looks like CMOS 4052 pin 2 (F) is connected
to a ceramic capacitor to CMOS 4052 pin 3 (E)... Then its
connected to IC4 pin 12.
Requires cutting the track between C22 and R57, here's how:
On my mx12, there is no C22 running to
R57. Heres how my columns are setup on my mx12, which is how they
are also on the diagram above. I have snipped, and sharpened the
There is a string of 6 capacitors and 6 resistors on the
solder side of the mixer board facing you. Locate C22 and R57
(see the diagram of the Superimpose section above). Note the
track that connects C22 and R57 (and on the reverse side this
connects to a track that leads to pin 2 of IC3).
Carefully cut the track between C22 and R57, isolating the
track that leads to IC3 pin 2.
Now, make a wire bridge (eg use wrapping wire) between R57 and
C22. Using cable connect H to the wire bridge.
Connect G to the track from IC3 pin 2 (that was isolated -
you'll find the end on the other side of the board).
You can tap the point at which IC3 pin 16 track meets the wide
power track as shown here.
I need help to find this on the schematic.
You can tap the ground track next to IC3 pin 8 as shown here.
Wouldnt it be ideal if we used shielded
wire to run these?
A to TP1
B to TP2
C to TP3
D to TP4
Created: Dec 27, 2015 by 1
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