MX12 modification web site

Acknowledgements / Disclaimer

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 been warned.

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

Features and Applications

What the modification does

Modification Process

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.

Tools and Requirements

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 information and steps explain the workings of the MX-12 and how to carry out the modification.

The following items are needed:


Schematic 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 file").

Step 1. Open the mixer.

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.

Step 2. Identifying the Parts

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 Manual.

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




Step 3. CMOS 4052. This is the heart of the modification.

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.

Brian's tips:

The following diagram shows the points of the chip that we'll be referring to throughout the modification.


Step 4. Getting to the Guts of it. Next part of the mod does the Luminosity part of the Superimpose effect.

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.

Step 5.

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 diagram above:

R53 -- C20
R52 -- C19
R58 -- C24
R56 -- C22 <<-- I have a suspicion that this is the one we need to modify
R57 -- C23
R59 -- C25



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).

Step 6. Connect I to +5 Volts.

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.


Step 7. Connect J to Ground.

You can tap the ground track next to IC3 pin 8 as shown here.


Step 8. Connect signal sources to A, B, C and D.

Wouldnt it be ideal if we used shielded wire to run these?

A to TP1

B to TP2

C to TP3

D to TP4


Step 9: testing



Step 10: Mounting and connecting the switch.