DL178 A Detailed Look At TV Testcard F & J

In this video i take a whistlestop tour of the classic Testcard F and it's Digital version Testcard J.

[brucedanton]

Thank you for this. As a member of the Test Card Circle, I do know a fair amount about Test Cards F and J, but what you are showing here adds much information as well. Thank you of course!!

[shaunhw]

The X (and the game's grid) on the centre of the screen, was placed there to make static convergence of the red, green (and blue) pictures easier, on "delta" type CRTs, which were the first kind of colour CRTs. Around the CRT neck there were four adjustable magnets. Three of the magnets were radial, at 120 degrees apart, mounted on a yoke, and each moved a different primary (TV additive primaries) colour. The blue gun would be switched off, leaving a yellow picture. The red magnet adjusment would move the red gun's screen diagonally from bottom left to top right, the green magnet adjustment would move the green gun's screen diagonally from bottom right to top left. The idea was to get the two colours at the centre of the screen on the X to completely overlap. Then the blue gun was turned back on, and the blue radial magnet (at the top of the yoke, or the bottom if the CRT was installed upside down as in some Thorn made receivers) moved the blue gun's screen vertically. The grid in the 0's and crosses was good for checking this. To complete the central registration, another magnet on a separate assembly could be twisted to move the blue screen horizontally. Once done, there were other controls usually located on a panel which could be accessed from the front of the television, to correctly overlap (dynamic convergence) the three colours in all the surrounding areas. This was done by the circuitry passing adjustable parabolic and sawtooth currents at line and field frequencies through coils in the convergence yoke. The noughts and crosses game, was specifically designed to check central area's RGB convergence. A crosshatch pattern was the recommended way, but these in the sixties and seventies were expensive, and the test card 'F' was a good alternative.

[johnr]

This is a very good video. I have to correct you on one thing. There were two delay lines on a PAL colour decoder. The luminance delay line was not a glass type. It was a a combined coil and capacitor which used long coil with a ground strip inside to form the other capacitor 'plate'. This effectively produced an LC transmission line for the delay. The glass delay line type was used for delaying the chroma signal by one whole TV line for the colour decoding process.

[scattygirl]

Only Connect reminded me of this childhood memory.

[arthurvasey]

18:00 This is Vrillon, from the Ashtar Galactic Command, speaking to you …

[Tangobaldy]

It's great to see your face. When you talk without video I feel like you giving a college lecture and I want to go skeeo. Your face fills in the blanks and makes the videos so much more pleasurable. Nice to see your enthusiasm. Also i woukd never read up about a test card but would always watch your videos as you made a mundane subject interesting. Thank you

[OC]

I'm old enough to remember Test Card C!

[cardiffguy]

Did you know that on the original test card F, the colour bars at the top were added electronically. The top of the test card had a similar display to the bottom (green and alternating black squares), except they were cyan and black. The colour bars as I said were added electronically by an engineer, So each day there were different amounts of the cyan and black squares on display, depending on how much they engineer dialled in the colour bars. Fun stuff eh?

[chrisnorth]

awesome work! And thanks for the clown nightmares now.

[philpem]

Test Card F was originally a colour slide (!)
For a while you could download a scanned JPEG of the slide from the BBC's website.

[merseyviking]

I always knew Bubbles the Clown was evil.

[frankowalker]

Loved the horror show at the end, I'm glad I did'nt watch it before I went to bed!

[davidcox]

We Love the BBC 2 TV Test Card F and G

[BigPauper]

Glad to see you dabble in the avant garde there at the end, haha. Great video as usual, lovely surprise there!

[KarlAdamsAudio]

Very interesting - here in Australia the Philips PM5544 pattern was pretty much ubiquitous.

[rowanlidbury]

As a kid I honestly thought she was sticking pins in it.

[furbearingbrick]

every copy of Test Card F is personalized

[glenslick]

Make sure to watch this video all the way to the end. I'm waiting for the horror movie where Testcard J comes to life and the evil clown drives a video production engineer insane.

[electronash]

SDI capture looks great, even after going through the GoogleTube mangle.

[rasz]

8:50 right half of last line is also missing in analog signal. Any idea what would be the reason?