Museum TV installation

[ppppenguin]

Made a tweak to the VHDL. At power up all registers initialise to logic 0 unless otherwse specified. This is fine for the registers that hold the values for Preview and BBC1 as this source is BBC1 off air. However the ITV and BBC2 registers also initialise to BBC1 off air. I added explicit initialisation to all 4 registers.

signal SELECTED_OUTPUT0 : std_logic_vector(3 downto 0) := "0000";
signal SELECTED_OUTPUT1 : std_logic_vector(3 downto 0) := "0001";
signal SELECTED_OUTPUT2 : std_logic_vector(3 downto 0) := "0010";
signal SELECTED_OUTPUT3 : std_logic_vector(3 downto 0) := "0000";

Wouldn't have been so easy in a hardware design. Would have needed to fit inverters before and after the relevant registers.

I pondered including an "Easter Egg". https://en.wikipedia.org/wiki/Easter_egg_%28media%29 But couldn't work up the enthusiasm to do it. My Tektronix 1755A vectorscope has an Easter Egg. Pressingthe right combination of buttons will give a screen full of fish swimming around.

[Nick]

...I pondered including an "Easter Egg". https://en.wikipedia.org/wiki/Easter_egg_%28media%29 But couldn't work up the enthusiasm to do it. My Tektronix 1755A vectorscope has an Easter Egg. Pressingthe right combination of buttons will give a screen full of fish swimming around.

The Tektronix 2232 has a Wizard on a skateboard if you press the right combinations of buttons... I used to have a 1240 logic analyser that would list out the engineering team names when the correct sequence was pressed.

Microsoft Excel 97 used to have a complete flight simulator hidden in it...

[ppppenguin]

All finished and ready for installation. Made a last minute change to the VHDL so that when it comes out of standby it resumes where it left off last time. So if (say) DVD was selected to BBC1 and the system is switched to standby it will come back to DVD when system is taken out of standby. Not 100% sure about this. Previously, coming out of standby always selected off-air.

Not sure which is better. I'll have another think and see if I can come with an even better way. Possibly choose between different options with a wire link behind the panel.

[Terry]

If anything can go wrong, it will!

I think the off-air option is better as it should always be available.

If somebody removes the DVD from the player after the system goes to standby, there won't be a signal when it is taken out of standby! (Presumably the Auroras will default to Test Card but what about the UHF modulator?)

If whoever takes the system out of standby actually wants the DVD feed, they only have to press one button, surely?

[Brianc]

I agree, Trevor. Always default to a signal that will "always" be present.

[ppppenguin]

Thanks for the opinions. I also asked the guys who will be using it most and they agree with default to off-air. So that is what it will be.

[ppppenguin]

Leaving for Dulwich soon to instal the new routers. I'll try to remember to take some decent photos.

[ppppenguin]

Fruitful day at Museum. The new audio/video router system came together fairly easily and works very nicely.

The new control panel is above the DVD player and waveform monitor. The actual routers are the 1U units with cream coloured panels towards the bottom of the right hand rack.

The next thing to be done is to acquire an MP3 player and load it with testcard music. This will be left running in a continuous loop feeding all 3 testcard channels.

Another minor addition would be a peak white generator. This is useful when doing RF level measurements as it guarantees full carrier on the +ve modulated System A. Without a substantial amount of peak white the RF level measurements can be tricky and unreliable. I think I have a few ZNA234 and ZNA134 SPG chips somewhere. Just need to add mixed sync and mixed blanking in the right proportions to get a peak white picture. No need for any refinements, just a resistive mixer to get 300mV of sync and 700mV of video into 75R. I also have SAA1043 SPG chips which would do the job. To be built on pinboard in a diecast box with a BNC at one end and socket for a wallwart at the other.

The Museum is chucking out a lot of stuff at the moment to gain much needed space. I came home with boxes of electrical fittings and a few vintage speakers. They'll all be on the Bring and Buy at Harpenden next Sunday.

[Radio Fixer]

Looks very smart Jeffrey. Well done.

Must have some stuff to bring for the B&B

Gary

[Raditechman]

Looks like a nice job, and well done.

John