A Question about PAL television sets

[dtuomi]

I was reading and replying in another thread about PAL implementations and as often happens I was told about the superiority of PAL because of its built in color correction and siting the superiority of having no tint control.

I personally think the built in color correction was a very compelling feature of the PAL color encoding system, so I'm not interested in that so much. What I am interested is in the implementation on a PAL set.

I assume that color phase (which is what the tint control is called on a professional monitor) was preset at the factory for PAL sets. That way the PAL set would be calibrated to the correct color phase and need no adjustments in the field (the above touted lack of tint control).

But is there a color phase adjustment pot on the inside of the set? For example, on a circuit card or color decoder board? That way if the set came out of adjustment it could easily be recalibrated?

I guess what I'm asking is did they just move the tint control from the outside of the set where it would be an end user adjustable control, to the inside of the set where only a repair tech would have access to it? Or was the factory calibration good enough where absolutely no adjustments were provided for?

Might be a stupid question, but it was just something I was curious about.

David

[ppppenguin]

There is no tint or hue control in a PAL set. Internal preset or otherwise*. If the demodulator phase is wrong, the colour simply desaturates slightly. In older decoders there would be presets for the U and V demodulator phase. Various ways to set these but disabling the PAL correction and tuning for minimum "venetian blinds" or "Hanover bars" was one possibility. If these controls are wrongly set the result is reduced tolerance of phase errors, reduced saturation and possibly very slight colour imbalance.


*This is not strictly correct The Thorn 2000 chassis had an unnecessary tint control that varied the R-Y vs B-Y gain. A gimmick and best removed. The early Sony PAL sets had an NTSC style hue control because they didn't have a proper PAL decoder. This is because of patent restrictions.

[dtuomi]

So there are only settings for the individual color components. That makes sense. Thanks for the info.

David

[Robert Grant]

A true PAL set did not need a hue knob because of the phase alteration by line (hence the name PAL).

The phase of the R-Y color information changes with each horizontal scan line. Every line where R-Y is transmitted is followed by a line where Y-R is transmitted. Since the B-Y is transmitted as such on every line, the "hue wheel" essentially is clockwise on half of the lines and counterclockwise on the other half the lines. Any phase error that would turn red toward orange in one line is cancelled out by the adjacent lines (in which red would be skewed toward magenta). A delay line memory is usually used to mix adjacent lines to avert flickering colors.

Pretty clever, eh? They managed to correct the one most frequently heard complaint about NTSC. It would haunt them in later years, because the alternating phase can cause trouble when doing the special video effects that became common in the 1980's.

FWIW, I'm almost sure that PAL sets had some passive component inside the cabinet to assure that the phase of the internal oscillator was reasonably close to the color burst reference on the back porch. As mentioned above, if the phase is too far off, color saturation could fall off.

It may have been in the form of a trimmer pot, or different tap points on the resistors in the oscillator circuit.

[andy]

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[jhalphen]

Hi Andy,

No hue control on DVB-T reception, but most modern LCD sets allow you to choose the Color Temperature of reference White. On consumer products it's labelled as 3 easy to understand settings Cool (7500°K) - Normal (6500°K)-Warm (3500°K).

DVT-T TVs with inbuilt tuner, never go through PAL: the MPEG2 stream (SD) or MPEG4 (HD) is directly decoded to primary components. If you purchase a DVB-T adapter which is our Euro-equivalent to your ATSC boxes, any Euro-TV produced in the last 30 years has a SCART connector, so the vintage set is driven in RGB. This has also the added advantage of allowed Teletext & inlaid EPG (Electronic Program Guide) as there is also a Fast Switch pin on SCART.

So you see, PAL is only used for TVs without SCART, the decoded digital stream being re-modulated onto a PAL B/G UHF carrier.

Hope this sheds a bit of light on current Euro-TV. Depending on countries, we will retire analogue between 2010-2012.

Pictures of a Rube-Goldberg device:
A Sony KV-1340DF, 12" Trinitron, France L standard only, purchased 1976, my first color TV. Here working with a DVB-T adapter or Sky Digital Sat TV, PAL out, PAL to SECAM transcoder (with the all-important "Bottles") TV modified to Monitor status. Had a Hot chassis so i built a series-regulated power supply to substitute the original PCB. I did that 25 years ago, to day i would have used a video-bandwith optocoupler.

Picture quality is still very good considering all the conversions...
And BTW, the CRT comes on to full brightness in 8 seconds in spite of its 33 years, a tribute to CRT technologies of the late 70s.

Best Regards

jhalphen
Paris/France

[ceebee23]

Many sets sold here in Australia for the past decade, both LCD and CRT have had the ability to handle NTSC through line in (rarely via RF)... and consequently often have "tint" controls but almost always available via remote controls using onscreen displays and the tint/hue control is unavailable during PAL playback.

Often when playing back NTSC DVDs or tapes it is necessary to change black level because of differences between PAL and NTSC.

Ironically now my BluRay player does a little upscale from 480i to 720p for most material and adjusts the black level/color space... it all seems so strange somehow I prefer the original 480i ...

Some early PAL sets had "tint" controls which really were just red/blue color balance not true phase adjustments.