FEATURE

ROADSIDE ASSISTANCE

A CLIP AROUND THE EAR

Phil Radlett, Eastbourne

Toshiba V71 VCR, Aiwa NSX-D858 DPL system, Goldstar CF-28C22 TV

When I play some Dolby Surround movies, especially films with noisy soundtracks, loud sounds, like explosions and gunfire, are often muffled. It’s like something is restricting the output to the speakers, to stop them blowing themselves apart. Is this caused by the VCR or the hi-fi system, and what can I do about it?

It’s just possible that one or more of the amplifier’s channels are being overloaded. However, a far more likely explanation is that the Dolby Pro-Logic decoder in your system is being driven too hard by the VCR. Loud dynamic sounds, like explosions, can generate large in-phase signals, causing the output from a lot of hi-fi machines and laserdisc players to exceed the Pro Logic decoder’s specified input level. This generates the characteristic ‘clipping’ effect you’ve described. Until fairly recently many DPL decoders had variable input level controls, to make sure this doesn’t happen, but few manufacturers seem to fit them anymore. See what happens when you switch off the DPL processor, and listen to the soundtrack in normal stereo; does the sound come through without clipping? If so you could try adjusting the signal level using an external attenuator. Something like a simple stereo audio-mixer -- the sort used for video movie-making would do the job -- they’re fairly cheap at around £15 to £20. Other than that your only other choice is to replace your AV amp or system with a DPL decoder that has an input level control.

NOISE ANNOYS

Jamie Mitchell, Norwich

Toshiba 2857DB DPL TV, Hitachi VT-F450 VCR

I’ve had my Toshiba TV and Hitachi VCR for around four months now, and I am generally quite pleased with the results. However, in the past few weeks a strange fault seems to have developed. Every so often, about twice an hour on average, I get a loud and very irritating clicking sound coming from the TVs rear channel speakers. It only last for a few moments but it’s not on the tape, and it doesn’t happen when I am watching normal TV programmes. Any ideas?

It may not be a fault. The regularity of the noise suggest that it could be caused by mains-borne interference. A lot of appliances produce a mains ‘spike’ as they switch on and off. Common culprits are refrigerators, central heating boilers and water pumps. Have you brought or installed anything like that recently? It may not originate from your home, it could be coming from a next-door neighbour’s house. The fact that you’re not hearing the clicks on normal off-air TV programmes might indicate that the interference is somehow being decoded as surround sound information by the TVs DPL processor. It may just be that it’s getting in through the VCR, which is more sensitive to this kind of interference. In either case the solution is to fit mains spike suppression plugs to your equipment. They’re readily available from good electrical dealers and companies like as Maplin Electronics, who also do multi-way sockets.  

SIZE DOES MATTER

Simon Kepple, Birmingham

Philips 8769 TV, Panasonic NV-F55B VCR, Kenwood KA-V7700 AV amp

I’m thinking of replacing my Philips TV, which has given stirling service for the past four years, but now I want something bigger, a lot bigger in fact. I’ve got around £2000 to spend, but I’m not sure whether to go for the largest 4:3 screen I can afford, or a widescreen model. I don’t want to get caught out and buy something that’s not going to be compatible with future developments.

As far as actual picture size is concerned, a large 4:3 display will always look more imposing than a 16:9 set of the same screen width, even when the 4:3 TV is showing a letterboxed image, but those black bars at the top and bottom of the screen can be intrusive. You usually get more convenience features and performance enhancing facilities for your money with big 4:3 sets, so that’s another point in their favour. As far as future compatibility is concerned forget it. Presumably you’re thinking about PAL plus and digital TV. The fact is no TV manufacturer can ever claim their products are future proof, for the simple reason that no-one knows what systems or standards are going to be used for digital terrestrial and satellite broadcasts. When it does happen -- possibly within the next couple of years -- you’ll be able to receive digital signals on any reasonably recent colour TV using a set-top converter box (or two...).

One thing you can be fairly sure of though, is that PALplus widescreen broadcasts are unlikely to extend much beyond the odd movie transmitted by Channel 4 and a couple of ITV regional companies, so don’t buy a TV on the strength of that feature. On balance I’d go for the big 4:3 set; you seem to have the audio side reasonably  well sorted, so there’s no need to be distracted by unnecessary facilities. Ferguson sets are pretty good value; the 37-inch T94N will give you the biggest bang for your bucks at the moment.

SCART SEQUENCE

M.R.Stanning, Bristol

Grundig GRD-200 satellite receiver, Sony SLV-E70 VCR, Sony KVX-2972 TV

I’m confused by conflicting advice from the instruction manuals for my VCR and satellite receiver, when connecting them to the TV using SCART to SCART leads. The VCR manual suggests it should be connected to the TV, with the satellite box plugged into the back of the video recorder. The satellite manual has it the other way around, with the satellite receiver hooked up to the TV, and the VCR connected to the satellite box. Which is right?

They’re both correct. The satellite receiver manual assumes -- quite rightly in most cases -- that it will be used with VCRs that have only one SCART socket. A lot of NICAM VCRs now have twin SCARTs but the majority of machines in use have only one. In which case you have little choice; the only way you can record satellite channels in stereo is to connect the VCR to the satellite receiver by SCART lead, with the TV connected to the satellite receiver , also by SCART lead. VCRs with twin SCARTs can be slotted in between the satellite receiver and the TV. Either way there should be no problems with picture or sound quality, provided you use the appropriately labelled sockets and good quality leads. The TV will auto-switch to external input whenever either device is switched on. The only point to watch out for is that when both the sat box and VCR  are switched on, the TV will normally display a picture from the component it is directly connected to.

PATCHY PICTURE

Gillian Keys, Streatham

Mitsubishi 25A5 TV, Sony SLV-E70 VCR, Pioneer VSA-730  Pro-Logic AV amp

About three months ago I brought the Pioneer 730 from a friend, it didn't come with any speakers, so I used some from an old hi-fi, and the performance has been very good. My problem though, concerns the TV, which now has red and green patches of colour along the sides and bottom edge of the screen. Could this be caused by the magnets in the speakers? They are about six inches from the side of the screen.

Got it in one! The metal shadowmask inside the picture tube has become magnetised. Normally it isn't a problem, and this occurs quite naturally with low-level fields generated by nearby metal objects, and the Earth’s own magnetic field.  All colour TVs have what’s known as a degauss system, that automatically demagnetises the screen every time it is switched on. A coil of wire is strapped to the back of the tube, around the back of the screen. The coil is fed with a burst of AC current, that quickly subsides, a few seconds before the screen comes on. The collapsing AC magnetic field erases any residual magnetism that builds up on the metal shadowmask or aperture grille.

The degauss circuit can deal with relatively small amounts of magnetism, it cannot cope with relatively strong local fields, like those caused by non magnetically shielded loudspeakers.  Ideally you should replace your speakers with magnetically shielded types, and move them well away from the side of the screen. The TVs degauss system may eventually remove the staining, however, if it doesn't disappear inside a couple of weeks you might have to have it seen to by a service engineer,  who will wave an industrial-strength degauss coil over the screen.

OUT OF CONTROL

Dave Sherman, Finchley

Akai VS-510

Almost every time I load a cassette and press record or play, the VCR spits it back out at me. I say almost, because each time I've had an engineer in to look at it, it behaves impeccably. The last chap offered to take it into the workshop, but said it would cost at least £50 to fix. It's obviously not that serious, otherwise it would do it all the time. Do you reckon it's something I could sort out myself, I'm quite handy with a soldering iron?

It's almost certainly something to do with a component called a 'syscon' (system control) switch, which is prone to failure, and gives the symptoms you describe. The switch -- actually a set of switches -- controls the sequence of operations of the deck mechanism. Syscon switches are quite delicate and if the contacts fail, or become intermittent  -- the most likely explanation for your machine’s behaviour  --  the deck can go haywire. If it is the syscon switch then it's a relatively straightforward job to replace it, though it's not something you can easily do yourself. To begin with they're not readily obtainable outside the trade, and even if you do manage to get hold of one, you need to know how to align it properly. The £50 quote sounds reasonable and is probably not far off the mark.

TAPE TRAUMA

S.Mansfield, Peterborough

Aiwa FX1500, Ferguson SRA1 satellite receiver,

I recently replaced my ageing Mitsui VCR with a shiny new Aiwa model. I gave the old machine quite a hammering and over the past five years I've built up a collection of more than 200 tapes. I now find that although the tapes play okay on my old VCR, more than a third of the recordings are almost unwatchable on the new machine, with the picture breaking up badly. I've tried playing them on a friends VCR with similar results. There's some classic stuff on those tapes that I would hate to loose. Is there any way they can be recovered?

It sounds as the deck mechanism on your Mitsui machine may have suffered from an alignment fault, that has produced a mis-tracking error, which your new machine cannot resolve. It's likely that your old Mitsui is the only VCR that can replay those tapes. If you can get it up and running  -- without having the deck realigned -- then you might be able to copy the affected tapes to your new VCR, though the quality is likely to be quite poor. It could be that some of the more advanced VCRs and full-size VHS camcorders, that have a facility called timebase correction, might be able to get a picture, it depends how badly out of alignment your recordings are.

ROOM WITH A VIEW

Elliot Crane, Norwich

Grundig MSS200 satellite receiver

I would like to be able to use my Grundig  receiver to watch satellite  programmes in the living room and an upstairs bedroom. Can I buy an extra long SCART lead, or would I have to do something with the aerial cable?

There are several ways of doing it, but whichever one you choose, you will have to make some compromises somewhere down the line. The aerial cable method is the easiest. This involves splitting the aerial lead, that plugs into the back of the TV, into two paths. Simple two-way aerial splitter boxes are widely available for around £20.  Make sure you use an amplified type, as the reduction in signal strength cause by so-called ‘passive’ splitters will result in a poor picture on both TVs. Alternatively, if your satellite receiver is connected to the TV by a SCART lead, you could run a lead from the satellite receiver’s RF output socket to the bedroom. In both cases the sound will be in mono; you will be able to watch the same satellite programme as the main TV, though with the second method you won’t get terrestrial broadcasts as well.  Unless you also use a remote control extender, you won’t be able to change channels. If picture and sound quality are important then you should use a SCART splitter box to run a separate AV feed to the bedroom, though you still won’t be able to change channels, without a remote extender.

Your other option is to get hold of a second satellite receiver -- you can pick up good second hand models for around £20 to £30 -- and use a dish feed splitter, or a twin LNB to provide a second feed for the bedroom receiver. Depending which method you use you will have either full or partial control over channel selection (splitters won’t normally allow a second receiver to change LNB polarity). The other problem is that you have only one viewing card, so only receiver can be used at a time to watch encrypted channels.

There are plans afoot to introduce what’s known as a ‘partner card’ scheme, that would give subscribers an opportunity to obtain a second viewing card. We understand that at least one major satellite receiver manufacturer has plans for a partner card receiver (two tuners in one box), that could be launched soon, possibly as early as next year.

---end---

Ó R. Maybury 1996 3107