|
HINTS & TIPS HE 112
Q
I have a Loewe Planus (100Hz) television and a Toshiba SD-2109 DVD
player. On some discs a thin green line (and sometimes red) that can be seen at
the top of the TV's picture. This happens on the main film disc, but strangely
doesn't occur on the disc featuring the extras, which has the same visible
picture proportions. Also, this only seems to occur on films that use the full
widescreen processing, not those that produce a letter-box picture. Is this a
problem between my DVD player and TV?
P Clayton, Twickenham
A
Compatibility problems with DVD players and TVs are actually quite rare
and normally affect every disc rather than the odd one. In this instance the
most likely explanation is a slight mis-alignment of the TV’s convergence
circuitry, which is responsible for ensuring that the red, green and blue
images are precisely aligned. The reason that it only shows up on widescreen
movies may have something to do with the fact that DVD extras are usually in
4:3 format. The TV electronically expands the picture to fit the 16:9 screen
and the change of shape usually results in some slight ‘overscan’, which puts
the top few picture lines, where the misalignment is most visible, off the of
the screen and out of sight. The simplest way to find out is to substitute the
TV or the DVD player; if the TV is responsible it should be a simple job for an
engineer to sort out.
QUICK TIP
The convergence adjustment on a TV is usually carried out using an
electronically generated grid or ‘crosshatch’ pattern of fine lines. When the
convergence is set correctly the lines appear white, any misalignment shows up
as a coloured ‘fringe’ or offset line from the grid pattern. Incidentally the
famous Test Card F – the one with the young girl in the middle – has two
convergence test patterns: a white grid for the outer edges of the screen, and
the game of noughts and crosses on the blackboard for the centre-screen area.
Q
I recently bought a Toshiba Picture Frame TV, as recommended in HE 98, and I've
noticed a slight buzz that increases with the picture brightness. The dealer
tells me it's due to the coils vibrating and that this is "within normal
operating parameters". They also told me this happens on all large screen
TVs these days. This noise is only noticeable during quiet dialogue, but
nonetheless it's still distracting. Can you tell me whether I should expect
buzzing from such an up-to-date TV or whether I have been sold a duck?
Paul Smith
A
The dealer is right about the noise being generated by the TV’s
deflection coils, he might also have added that noises can come from the EHT
(extra high tension) components that generate the high voltages used to drive
the picture tube. The tube itself can crackle and make hissing sounds in very
dry or excessively humid conditions, mains power supplies hum and whine and the
horizontal scanning circuitry generates a high-pitched whistle; in other words
most TVs are far from silent (see also Getting Started). However, exactly what
constitutes ‘normal operating parameters’ is open to interpretation, but you
shouldn’t notice any noises at living room volume levels. If you feel that your
TV is excessively noisy you have every right to insist that something is done
about it but before you do, listen to a few other TVs, preferably under similar
conditions, to make sure you haven’t become overly sensitive to this one noise.
Q
I have a Bush DVD 2004 player coupled via and S-Video connection to a 28-inch
Sony TV. When playing Monsters Inc. the player displays all of the menu options
but won’t allow me to access them so it stops after three seconds. At first I
thought it was the fault of the DVD disc, so I replaced it, three times, and
none of them have played. In the end I had to resort to buying the movie on
VHS, for the children's sake, but I'd much rather see it on DVD. I have about
15 Disney DVDs and they've all been fine. Can you help?
Jason M Clary
A
There have been a few reports of compatibility problems with this
movie, though to date most of them have concerned layer change on Pioneer
players. This sort of thing used to be quite common in the early days but both
disc producers and player manufacturers seem to have got their acts together
and there have been very few incidents lately. However, before you take the
player back, run it through with a disc cleaner, just in case there’s dust or
fluff on the optical pickup (though this usually causes problems on all discs);
you should also confirm that it really is the player and not the disc – just in
case all the copies you’ve tried were from a dodgy batch – so try it out on
friend’s player or ask the shop to check it out.
QUICK TIP
A lot of early DVD compatibility issues concerned layer change where
the player’s optical pickup was unable to switch focus quickly enough, (or at
all), to read the second data layer on some DVDs. Most recent problems have
been to do with various players inability to read or process the increasing
amount of PC multimedia content that’s appearing on discs. In most cases the
problem has been solved by updating the player’s ‘firmware’ (the software that
controls the player), either by playing a special disc or by swapping a
microchip inside the machine.
Q
I have a Grundig Digibox and if I set it to RGB output the picture moves about
3mm up the screen. This is particularly annoying when watching football, where
the score is positioned at the top of the picture. Also, when watching Sky's
cricket coverage, the blue info bar at the bottom of the screen becomes very prominent.
However, if I change the output to PAL and suffer the poor quality, the picture
is positioned fine. I had the engineer round, but he said it was a
"transmission problem". Any ideas?
Ed Bowden
A
That sounds like a fairly typical fob-off line from an engineer who
either can’t or won’t fix the problem. In theory there shouldn’t be any
difference in position between pictures from composite, S-Video and RGB feeds.
In practice it’s difficult for TV designers to avoid and there is often a very
small displacement but it should be never be enough to cause the kind of shift
problem that you have described. There’s a very small chance it could be down
to the digibox but it’s far more likely that the TV is need of a tweak, it may
not be possible to eliminate the shift completely but a good engineer should be
able to adjust the picture geometry (see also Getting Started) to minimise or
compensate for the effect.
Q
I’m thinking of buying a Pioneer DCS-303 system. I have just read some
reviews and have a few questions.
1. The DCS-303 has Dolby Pro-Logic II; does this mean that if I record
(using a VHS recorder or a DVD recorder) or watch in stereo on the TV, I
will hear it through all five speakers?
2. When the price is reasonable, I want to purchase a DVD recorder. Will
I be able to plug it into the DCS-303 and still use it as a home theatre
set-up?
3. Can I use my VCR with the DCS-303? I'm still recording movies off the
TV and I'm wondering whether when I play it back the DCS-303 will
provide sound from five speakers?
Robert Fleming.
A
1. Pro Logic II creates a stereo rear channel from Dolby Surround
soundtracks, so yes, you will hear sound coming from all five speakers (front
stereo, front centre, rear stereo surround).
2. Yes, you’ll be able to plug a DVD recorder into your DCS-30, it has
an optical bitstream input, so you’ll hear Dolby Digital and dts movie
soundtracks in all their glory through your system.
3. Yes again, the DCS-30 generates a 5-channel surround sound from
4-channel Dolby Surround and even stereo and mono sources but in the case of
the last two the effects on the surround channel will be artificially derived.
Pro Logic II is a very clever idea but the fact remains that what you are
hearing is a fake, and it will be up to you to decide whether or not the effect
is pleasing.
Q
I have a Panasonic TV that has one SCART connection, a Panasonic NV-FJ630 VCR
and a Reoc A3 DVD player. I bought a five-way SCART
adaptor and a second SCART lead but when both leads are connected to the
adaptor volume brightness is reduced. If I disconnect either lead while using
the other the sound and brightness go back to normal. I don't know if this is
to do with the adaptor or the SCART lead?
Shiranthi
A
It sound a lot like the SCART adaptor is to blame and there are a
couple of possibilities. You may be using the wrong type, there are basically
two options: there are simple ‘splitters’, where all of the plug and socket
pins are wired together in parallel, and ‘switchers’ where only one input is
connected to the output cable at a time. A splitter is designed for signal
distribution, i.e. one input with several outputs, so if it’s used incorrectly,
in an ‘input’ mode, the signals will interact with one another. The other
possibility is that you are using a switcher type adaptor, but there’s
something wrong with it, or it’s a flaky design, that’s affecting the AV
signals, or allowing them to interact. If the adaptor is an expensive item,
from a reputable brand you should take it back, otherwise a new ‘switched’ adaptor
is called for.
QUICK TIP
SCART switchers come in a wide variety of shapes, sizes and
capabilities. The cheapest ones have a simple manual mechanical selector
switch, or a row of push buttons, which is obviously inconvenient as it means
you’ll have to keep getting up out of your seat to change inputs. The
alternative is an auto-switching type that senses when an input is active and
routes the AV signals to the output cable. However, if your TV only has one
SCART socket it’s probably getting on a bit and about time it was
replaced…
Q
I have recently invested in a Miller & Kreisel K3 speaker system (3 x
K7s, 2x K5s) and have partnered this with a REL Q150E subwoofer. I'm
very happy with my buy, but I do have a problem. I used to have a Yamaha
YST-SW40 sub that had an auto-off switch, which shut the sub off when not in
use. I know these are often frowned upon, but I found it very useful. The REL I
have now doesn't have this feature, and the instruction manual says the sub
will be fine if it's left on continuously. However, the worrying thing is when
any other appliance in my house is switched on or off at the mains, the REL
omits a 'thud'. Is there something wrong with it and will it do any harm?
Ian Forster
A
It’s probably not a fault but it may suggest careless design. It’s
unlikely the odd thud will do any damage but if it’s happening a lot, or
they’re loud then you should definitely put a stop to it. It’s likely that the
sub is reacting to momentary high voltage spikes that ride around on the back of
the mains supply. These are unavoidable and are caused by appliances containing
motors or inductive components switching on and off. Spikes and surges can also
be generated by the supply grid and even lightning strikes but wherever they
come from the power supplies in most mains powered AV devices should filter
them out. If, as seems likely the sub’s power supply isn’t dealing effectively
with the spikes then you should try an anti-surge/spike mains adaptor. They’re
cheap and plentiful and readily available from electrical and electronics
retailers, computer stores and even good old Woollies.
QUICK TIP
A few sub woofers with auto power have come in for some stick, not
because the feature is inherently flawed or that it affects sound quality, but
it’s all down to timing. In an ideal world a powered sub will switch on more or
less instantly, as soon as it senses a signal from the amplifier or decoder,
and switch off soon after the signal has disappeared. Getting the switch off
delay right is crucial otherwise a powerful sub, with the wick turned up high,
can be left emitting an annoying hiss for several minutes.
Q
I recently bought a Philips DVDR 890 DVD recorder, there was a glitch so I took
it back and it was exchanged but the second one was the same. The problem is
when recording from VHS camcorder tapes through the EXT2 (SCART) connection the
results are, at times, appalling. The
picture is very bright and saturated with colour and little detail. I've tried
using different tapes, various video sources, two cables and three types of
DVD+R disks but I'm ending up with a lot of coasters. Philips Customer Care
suggested feeding the source via the TV and recording from that using the EXT1
SCART and this appears to work but the only problem is you cannot view anything
else while recording.
Chris Martin
A
The fact that Philips came up with such an oddball (albeit effective)
solution suggests that it’s something they’re well aware of and just before we
went to press Chris contacted us to say that Philips had advised him that the
problem was being looked at and that he should return the player and request a
refund…
It’s looking increasingly likely that this is inherent in the design,
possibly something to with the machine’s Macrovision copy protection system, which
is meant to stop users running off DVD copies of movies on tape. If that is the
case there probably isn’t an easy or quick solution though if anyone out there
has got a DVD-R890 and one of those so-called ‘copy enhancer’ gadgets that
strip out Macrovision protection they might like to try a few experiments to
see if that solves the problem, and don’t forget to let us know how you get on.
QUICK TIP
It hasn’t happened yet but as and when recordable DVD takes off it’s
likely that there will be a rapid influx of cheap and unbranded blank discs.
The CD-R/RW market is awash with the stuff, much of it second-rate and there’s
even a suggestion that manufacturer’s rejects are turning up on bulk buy
‘spindles’, labelled as top grade media, and sold at Computer Fairs. At the
moment only a small handful of plants around the world are making DVD blanks
and so far the quality seems to be fine but watch out for deals that look too
good to be true…
BOX COPY 1 – TV PICTURE GEOMETRY
Ensuring accurate picture shape or geometry on a cathode ray tube (CRT)
display has been an enduring problem for TV manufacturers. One of the most
difficult things to get right is linearity, which is a measure of the picture’s
horizontal uniformity. In other words, if you were to look at a picture of a
ruler on a properly set up TV the markings would be evenly spaced but if the
linearity is out of bonk the ruler will appear to be stretched or compressed
along its length.
Correct linearity on a 4:3 TV is not too difficult to achieve but it’s
been a headache for manufacturers of large 16:9 widescreen sets. That’s because
the image is ‘drawn’ on the inside of the screen by a moving beam of electrons,
streaming from a ‘gun’ in the neck of the tube. The beam is moved around the
inside of the screen by a powerful magnetic field, generated by a set of coils
mounted around the neck of the tube. The wider the screen the harder it gets
since the speed at which the beam traverses the screen has to be precisely
varied, to compensate for the changing distance between the gun and the screen,
because it has further to go to reach the outer edges of the screen, compared
with the middle. Linearity, like
convergence and focus can all drift as the tube and the electronic circuitry
ages, which in the past meant that a TV required regular servicing. Nowadays
most TVs automatically compensate for the changes and usually require little or
no adjustment throughout their normal working lives, which is typically 6 to 8
years.
BOX COPY 2 – NOISE ANNOYS
With the notable exception of LCD panels almost all video display
devices make some sort of noise. The loudest noise in a cathode ray tube (CRT)
television is undoubtedly ‘line whistle’, though the good news is that it
becomes much less of a problem as you get older. The whistle is produced by the
TV’s deflection coil circuits, which oscillate at around 15kHz. This frequency
is just within the human hearing range – normally cited as between 20Hz to
20kHz -- though once we get past 25 our sensitivity to higher frequencies drops
off sharply (markedly so in men, which suggests that women should make better
music and hi-fi reviewers…).
Of the alternative display devices on the market CRT, LCD and DLP video
projectors are the worst offenders because all models have large and powerful
fans or extractors that have to run all of the time, to cool the high-intensity
lamp. Many rear projectors – in particular LCD and DLP types -- also have
cooling fans but naturally ventilated CRT models generate a line whistle and
have high voltages flying around inside that can produce crackles and hisses.
You’d think plasma screens might offer some relief but no such luck, many
models have cooling fans – some early ones had half a dozen or more of them –
but even more recent panels that rely on convection cooling and ducted vents
still produce high voltage crackles and contain large, gently humming or
whining mains power supplies.
---end---
Ó R. Maybury 2002,
0711
| 
