On Tue, 19 Aug 2003 10:29:28 +0100, tony sayer
wrote:

In article , Don Pearce
writes
On Mon, 18 Aug 2003 20:17:30 +0100, tony sayer
wrote:

FWIW I've yet got to see a picture as good as our 7 year old B&O as long
as its got a good analogue PAL signal that is!..
--
And where do you find a good analogue PAL signal these days? I'm
direct line-of-sight to Crystal Palace and I don't see pictures as
good as those of 20 years ago.

d

_____________________________

http://www.pearce.uk.com

Well we receive a very good signal from Sandy Heath in Bedfordshire. In
fact its better now that what it has ever been especially in respect of
background noise and artefacts etc. Its now fed via high rate digital
fibre and encoded to PAL on site and hence the picture when the source
material is good, then the results follow suit.

Does seem a bit sad that it happens like this though I've always
believed in digital transmission if, and only if, the bitrates are high
enough!..

Suprised that you can accurately remember piccys from over 20 years ago
Don. Having said that I remember when the Philips K9 chassis using the
colour difference drive came out, and we were blown away with how good
it all was....

I was in the business, Tony. I could grade an image on the CCIR scale
within about 0.2 - can't any more. But what I remember most clearly
was the super-realistic skin tones, and the full PAL-I resolution
which registered every hair on the head of a close-up. It all just
looks blurred now.

I know that the fault is not digital as such, but the implementation -
meanness with bit rates particularly. The problem is that once the
quality is gone, it is gone for good. All digital STBs seem to use the
same trick of ringing edges to simulate a sharp edge, but it really
does look awful.

d

_____________________________

http://www.pearce.uk.com

In article ,
Don Pearce wrote:
I think the overscanning thing is just manufacturers making sure you
never see a black edge anywhere - picture all the way to the edges. It
also slightly ameliorates the effects of letterboxing. You lose a load
of picture, of course - but who's counting? You should be able to
shrink the picture a bit by upping the EHT - care to try? ;-)

It's more, as Jim says, to make the picture look as 'large' as possible
in the showroom. It's been common practice to overscan sets since day one.

As for picture quality generally - particularly gamma, I think there
is a combination of things going on. The modern high-brightness
phosphors do seem to have rather strange gamma curves, which
presumably can't be corrected terribly effectively. And I'm sorry to
say, I think that QC in the broadcast business isn't what it should
be, particularly with the number of hops it takes a signal to get from
a studio to you. Blacks and peak whites get squashed and can't be
recovered.

I can't see why the phosphors would have any effect on the gamma. But
you've got to remember that plenty of programmes are very variable as
recorded. Black level and the detail in the blacks is perhaps the most
difficult thing to maintain throughout the chain.

--
*If love is blind, why is lingerie so popular? *

Dave Plowman London SW 12
RIP Acorn

In ,
Jim Lesurf typed:
I had suspected there might be a 'service engineer' menu hidden
somewhere, but had no idea how to find it. If you can explain how I
can find this and I can adjust the image size in the various modes,
it would be excellent. :-))

Here you go:-

Originally posted by

==================================
WRITE DOWN ALL THE ORIGINAL VALUES BEFORE CHANGING ANYTHING. ADJUSTMENT
IS AT YOUR OWN RISK AND I TAKE NO RESPONSIBILITY FOR ANY DAMAGE YOU
INFICT ON YOUR SET ARISING FROM THESE INSTRUCTIONS.
==================================

Bass to max
treble to min
hold down "index"
press "-" (minus) on the front of the set.

this will get you into the service menu.(it will default to 16:9 mode
makes things a bit tricky for 4:3 geometry but it is possible)

coloured fastext buttons on the remote navigate left to right they a
back/forward/adjust up/adjust down : last two might be reversed but you
get the idea.

"STR" saves new value: if you modify a setting and don't press this then
the value will go back to its previous value when you move out of it.

"N" gets you out of the service menu.

settings are :

H-pos (horizontal position)
V-pos (vertical position)
H-amp (horizontal amplitude)
V-amp (vertical amplitude)
EW-amp1(EW-amplitude coarse pincushion looks like)
EW-amp2(EW-amplitude finer/corners looks like)
Trapez1(Trapezium comp_ suck it and see!)
Trapez2(finer of the above suck it and see!)
V-lin (vertical linearity)
V-sym (vertical symmetry used with above to sort vertical linearity !)

You can mess about with the above settings with impunity. They are all
fairly intuitive and relate to centring , overscan , geometry ,
linearity and are interactive with each other. However avoid going to
extremes on any settings (you won't need to anyway) as it might kick in
some sort of protection and collapse the picture (thin horizontal line)
which will probably burn the tube in about three seconds flat and you
will no longer be able to see the service
menu to undo your error!

The others are*these ones should not be played with*)

DVCO (take a guess at deflection voltage cut-off/correction??) : leave
it alone you need a PAL colour bar for it to auto adjust to. (more info
to follow )

Cut-off (cut-off DC leave well alone)
Ug2 (avoid like the plague)

Hi-light & lowlight (RGB cut-off and drive adjustments for colour temp:
leave alone unless you have a colour analyser handy and know a thing or
two about CIE chromaticity aims) "warm" seems close to 6500K anyway : I
intend to check grayscale tracking properly at some point.

Sub-brightness (pedestal black level: sets lowest point on the
brightness control basically)

I strongly suggest that you avoid adjusting any of the the ones above as
they are either very vague(technical) in their purpose or have the
possibility of damaging the set or both!

-------------------------------------
Some advice about adjustment.

Write down all the original values BEFORE you start adjusting things.
this is the only way to return to the original settings if you cock
things up.

Don't go to extremes on ANY setting. The settings are all interactive to
a certain extent.Proper adjustment involves ping-ponging back and forth
between adjustments to ensure you are not over-compensating for
something another setting is doing. Balance remember.

Use relevant test material (Video essentials is good but remember it may
not be 100% for a 625/50 image: its actually pretty close on the PK1 so
don't worry about it).

Make sure you are looking at the relevant input type before engaging the
service menu( on the PK it looks like one lot of settings applies to
everything: which is actually good in a way).

When adjusting geometry I initially center the image (H-pos V-pos) then
take off the overscan (V-amp H-amp) so I can see the edges of the image.
Get everything pucka geometry wise (make sure all edges are straight as
poss and the scan is linear (no bulgy distortion). Then put on the
overscan (H-amp V-amp equally) until things start to go out of kilter
(and they will) readjust for optimum and then more overscan etc until
satisfied.

Big tip: Use a ruler and or set-square (nice big ones) do not trust your
eyes with geometry issues.

Take your time: the geometry alone might take some time.(the concave 4:3
takes a bit of time to fix). You may not be able to get everything
perfect (trust me) but you should be able to improve the bowing problems
until its unobjectionable.

The more accurate the 16:9 adjustments are the more accurate the 4:3 is.
But you may still need to come out of the service mode to check those
nasty concave sides in 4:3 and pop back in to change a setting that
fixes it (without compromising the 16:9 mode at the same time!)

Properly set-up the PK1 kicks butt!

In article , Steve
wrote:
In , Jim Lesurf
typed:
I had suspected there might be a 'service engineer' menu hidden
somewhere, but had no idea how to find it. If you can explain how I
can find this and I can adjust the image size in the various modes, it
would be excellent. :-))

Here you go:-

[big snip]

Superb!! :-) Many thanks for that! I have now adjusted the overall image
size so that the displayed image actually fits onto the screen. I'll have a
play later to sort out pincushion, etc...

Is there a news group you would recommend for things like this, and for
similar info in DVD players, etc? i.e. a useful technical info group for
the uk on Television, DVD, video, etc?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article ,
tony sayer wrote:
Be that as it may, how come the analogue pictures sharper?..

Your set is probably ringing on analogue.


Dave. I did spend quite a few years in the TV industry at both ends
please!..

Well, what's your explanation, given that digital has a wider bandwidth
than analogue?

--
*Why don't sheep shrink when it rains?

Dave Plowman London SW 12
RIP Acorn

Dave Plowman wrote in message
...
In article ,
tony sayer wrote:
Be that as it may, how come the analogue pictures sharper?..

Your set is probably ringing on analogue.


Dave. I did spend quite a few years in the TV industry at both ends
please!..

Well, what's your explanation, given that digital has a wider bandwidth
than analogue?

I don't know what bandwidth most digital channels are broadcast at, but I
generally see a lot of MPEG artefacts on digital telly. That's through NTL
(IIRC their signal comes from terrestrial digital, and is then bunged into
the cable network).

In article ,
Doki wrote:
Well, what's your explanation, given that digital has a wider
bandwidth than analogue?

I don't know what bandwidth most digital channels are broadcast at, but
I generally see a lot of MPEG artefacts on digital telly. That's through
NTL (IIRC their signal comes from terrestrial digital, and is then
bunged into the cable network).

The artifacts are a separate issue from the resolution. Also, something
which is re-broadcast down cable depends on the interface equipment etc
being up to standard - and that's not usually a fact of life with cable
companies.

--
*I didn't fight my way to the top of the food chain to be a vegetarian.

Dave Plowman London SW 12
RIP Acorn

On Thu, 21 Aug 2003 17:47:44 +0100, "Doki"
wrote:


I have one of these, should have the service menu codes somewhere. IME the
geometry alters when there are white titles scrolling up on a black
background etc. Not particularly impressed. OTOH, I've got a Philips I got
cheap, "BlacklineS" apparently, curved screen (not as curved as some,
similar to an FST monitor), and the geometry is far better on that. I think
flatscreens seem to have more geometry problems.

When picture size changes depending on the amount of white on the
screen, the cause is poor EHT voltage regulation - the extra beam
current causes the voltage to sag, and the scan signal can then drag
the slower beam further. There really is no excuse for this in a
modern TV, particularly an expensive one.

d

_____________________________

http://www.pearce.uk.com

In article , Don Pearce
wrote:


When picture size changes depending on the amount of white on the
screen, the cause is poor EHT voltage regulation - the extra beam
current causes the voltage to sag, and the scan signal can then drag the
slower beam further.

You may be correct with the above diagnosis. My own suspicion was that the
return resistance for electrons flowing off the screen front is too high -
particularly for areas near the middle of the wide screen. This means
bright areas build up a noticable local -ve charge, deflecting the beam as
it approaches the screen, thus 'spreading' the image. This view has been
supported by the very noticable 'static' field near the screen at times
which causes the hairs on my arms to stand up.

However my diagnosis does not explain why the 'bulge' effect is much more
noticable in the width than in height. i.e. I get deformation of the image
sideways, but don't notice it vertically. For that, you explanation may
well be more sensible.

There really is no excuse for this in a modern TV, particularly an
expensive one.

I must admit that it surprised me that the TV does this. However to be fair
I suppose that for a widescreen TV it is not an 'expensive' model, so
corners may have been cut. The effect is not enough to bother me very much,
and tends to only be noticable on 4:3 format in the center of the screen.

TBH I was also dissapointed by how poor the TV's inherent sound system was.
Not just 'boxy' as I'd expected, but also audible hum from the speakers
when you get close - even with the set volume at zero. Fortunately, I have
arranged things so this does not matter. :-)

Reducing the image 'overscan' so the image now fits as I would say
'properly' seems to give a better image. I have not noticed any need as yet
to fiddle around with other parameters. The sizes only needed to be changed
by about 5-10%.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Doki
wrote:


I know. My cheapo Philips set doesn't have it. The Panasonic PL1 was
regarded as one of the best flatscreen TVs when we got it, but I'd
sooner watch the Philips anyday

TBH I bought our Panasonic without taking the process very seriously. My
suspicion is that with factors like digital terrestrial transmissions and
recordable DVD formats things are currently changing quite swiftly. Hence I
regarded the TV as an 'interim' item. I suspect that in 3-5 years it will
be replaced with something better that may well have an inbuilt digital
receiver, etc, and may be LCD or similar. [1] For watching films from DVD
the Panasonic is 'better' for me than the old B&O as that was, alas, simply
too small a screen. The Panasonic also supports stereo, so is better in
that respect, albiet its inherent sound is poor in my judgement.

Slainte,

Jim

[1] And if the force is with us, may even have a decent gamma :-) Mind you,
the one LCD computer montior I tried, I hated. So I have my worries about
visible pixels and glare from LCD TVs... My suspicion is that the CRT still
has 'legs'... But time will tell... :-)

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html