View source for The Mux

The '''''main mux''''' is the huge black thing in the [[AV rack]]. It routes video to different places, and also has analogue TV demodulator inputs. It's controlled by an outboard box which sits on the Director/Vision Mixer's desk.

==Functions==

* 32 input to 4 output matrix

==Faults & unknowns==
*2 composite inputs to the matrix are dead.

==Explanation of operation==
This was originally based around a PIC16F84 with an 8MHz crystal containing code written by [[hist:Rob Sprowson|Rob Sprowson]], the code for which is now lost.

A new PIC, a PIC18F2455 using a 20MHz crystal, has replaced this PIC through use of an extra 'daughter' board. This change in PIC was to allow easier coding, using C instead of assembler, and to provide USB capabilities. The source code has also been lost.

It now runs on an installed Arduino, and is one of the first [[YVP_Protocol|YVP Protocol]] compatible devices. This does mean a computer is needed to control it however, connected to the now real, RS-232 compliant serial port on the back.

==Power supply==
This is very much the weak point of the mux, and is tied up with why there are loads of unconnected [[BNC]]s on the back. - The Mux used to hold a distribution amplifier for creating 8 outputs of each main output from the matrix. Sadly though, this experienced some heavy cross-talk, and was misdiagnosed as "electric fields". The original creators now propose that simply adding better decoupling to the power supply would have solved the problem.

There are two mains transformers:
* 2x6V
**50VA
**powers + and - 5V rails

*2x6V
**3VA
**wired as 1x12V, 3VA to provide the +12V rail.

All the supplies are smoothed with big electrolitics, and then regulated with 78/79 series regulators.

All this is built on a length of chocolate block connector strip, with a lot of stranded hookup wire.

[[Category:Technical]]
[[Category:Vision Path]]