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Satellite Workshop 54

Jack Armstrong

Following on from last month's discussion of Pace Digibox repairs, I thought you might like more information on the Digibox.

Since the unit was first sold, some significant changes have taken place but, equally, some very desirable ones have not. Most notable was the introduction of "Open" which allows the user to access a kind of "mini internet" where companies such as the Ford Motor Co. can advertise their products. The telephone connection sends the user's requirements to the main computer and the pictures and text are then transmitted back to the Digibox. I suspect this happens partially via the satellite transmission and partly via the telephone line but I don't know the exact technical arrangements. You can also obtain an e-mail address which allows you to type, send and receive messages via the Internet. A separate infrared remote operation keyboard can be purchased to make this task much easier to carry out from the comfort of your armchair. The actual cost of using the "Open" service is "normal BT rates plus 1p per minute" while your telephone line is in use. You can tell when the line is in use by looking for the tell-tale LED on the Digibox front panel.

Unfortunately, the Digibox does NOT provide true Internet access apart from e-mail. You can't access web sites and you can't access Usenet News Groups. Both of these form a most valuable source of information for both children and adults, although children need to be monitored as they can quickly find questionable material as well as useful information. In this respect, parents might be thankful that Internet access is not currently provided.

The Digibox also provides a most useful Electronic Program Guide - a sort of enhanced Teletext which lists current and future programmes and allows you to select the one you want without having to push numbered buttons. In addition, a few programmes carry subtitles, although this is not yet fully implemented and some manufacturer's software does not allow it to work properly. Hopefully, the problems will already have been resolved by the time you read this.

The reason for such problems is that each of the four Digibox manufacturers has provided similar - but not identical - hardware. The BskyB software which looks after encryption and access has to be matched to the manufacturer's software which interfaces directly with the hardware. As BskyB continually downloads software updates via the satellite transmission, so each manufacturer also has to provide BskyB with its own modified software, to download, in order to maintain compatibility. It seems that the two can get "out of step". In fact, any Digibox that is installed after sitting in a warehouse for a month might not work at all until the latest software has been downloaded.

While everyone involved has worked hard to get the "Open" service working for British Interactive Broadcasting (did you accept discount in the form of a "BIB subsidy"?), the work on other features has, apparently, taken a back seat.

For example, there is no timer facility to enable you to set the Digibox to select a particular program at a specific time, so recording is a headache. In addition, some "Pay Per View" movies have a special pulse added to prevent a modern VCR from recording them. This can be circumvented by buying a special "picture enhancing" box or by using an extremely old VCR to record the pictures (a good reason to get your old VCR repaired?) I suspect that the timer facility might never be added to the software on current Digiboxes but will appear on the new generation ones that have a built-in Hard Disc Drive which will save several hours of programmes in a compressed form. The advantage (to the program provider) of this technology is that subsequent recordings will erase current ones, so you won't be able to build up your own "video library". The advantage to you is that it will reduce the current need for a "spaghetti junction" of wires behind the TV. By the way, you can get a Scart Switching box that allows you to select any one of up to four devices. So you can feed pictures and sound from your DVD player, Digibox, VCR or on-Digital box to your TV. You can find a switching box that is semi-automatic and has a remote control handset at the TopSat web site. ( For a low cost manually operated scart switching box, contact SatCure (

Interestingly, Panasonic have come up with an answer to the lack of timer facility by building into their latest VCRs (NVHD675 and NVHD685) the ability to control the Digibox via infrared signals. No doubt other manufacturers will be following suit. It is also possible to use a slightly older VCR, with the I/R control feature, to control the Digibox even if the Digibox control codes are not included. However, you have to build a special interface to do this and such a chore might be beyond the capability of most users. Information on the codes and how to build the interface can be found at the web site:

The Digibox will provide stereo sound but there is no provision for Dolby "digital" surround sound, although Sky News reported on February 13, 2000 that BskyB was investigating the possibility of an upgrade in the future.

Lots of people have asked me "Can I use a Digibox outside the UK?"
The answer is a qualified "yes" but bear in mind that BskyB is obliged to try to prevent it. They pay a fee to broadcast a programme to a specific area. If they broaden the area of reception then they have to pay a much larger fee to the film providers. The end result would be the people of Britain effectively subsidising the viewing of a relatively small number of ex patriots. As always, it comes down to a question of finance. Of course, if you buy the Digibox and install it in the UK, then get a smart card by subscription and have it authorised, there's nothing to stop you taking it somewhere else. BskyB will only find out if someone tells them or if you connect it to a telephone line, in which case they will be obliged to take steps to prevent you from viewing their programmes. If they do that, don't expend a refund as you'll be in breach of contract! Also, don't sign the BIB subsidy agreement as you won't have a telephone connection. Of course, this means that Pay Per View programmes will not readily be available to you and you won't have access to "Open".

Another common question is "Can I use the Digibox to view programmes from other satellites?" Well, the Sky Digital broadcasts come from an Astra satellite cluster at 28.2 degrees E of S. It IS possible to watch some unencrypted programmes that are not included in the Sky Digital package but the "Symbol Rate" of the Digibox is very limited and the software tends to be somewhat unreliable when the dish is not pointing at 28.2 E of S.

Satellite Workshop fault reports

"Got problems with my Oyster".
I could barely make out the speaker's face since his mobile home was parked across my window.
"Sorry, I think you want Charlie the fishmonger, just up the road."
"The Sky keeps dropping out".
This brought back memories of "Chicken Licken" from books read to me as a child. There's really no answer to an assertion that the sky is falling so I tried to usher this lunatic towards the door. He protested vehemently.
"Just climb the ladder and have a look at it".
"Thanks. I can see the sky from here and it looks just fine when your van isn't blocking the sun".
"It's not a van! It's a mobile home and it cost sixty grand and the Oyster probably wasn't cheap, either. Just climb the ladder and look at it".

Reluctantly, I allowed myself to be pushed towards the rear of the van. There was a ladder there and I wondered if it would really take my weight. However, the owner of the van had most of my weight on his hand as he pushed me up the ladder. Once level with the roof, I could see a white, circular object that looked like the trapdoor of a submarine.
"I'll turn it on!" came the voice from below.
As I teetered on the ladder, the circular trapdoor suddenly swung open then rotated. It was a satellite dish and, printed on its face in large letters, the word "OYSTER" confronted me.

Inside the van, the owner explained that he had bought the entire mobile ensemble from a previous owner who had had the satellite system installed by a specialist. The electronics consisted of an Amstrad SRD750F (known as "Chernobil" in the trade, because of certain things that happen in the power supply!) and something I'd never seen before called a "Ten Haaft" receiver with "Digital Audio". To get picture and sound, the two had to be used in tandem. The "Ten Haaft" controlled the position of the "Oyster" dish and the SRD750F accepted the analogue Sky card. I pushed a few buttons and everything appeared to work just fine, although it was decidedly tricky to match the correct audio with the picture!

"Of course, it's all right now but, when I'm mobile, the stupid dish goes up and down and round and round and can't seem to lock on, so the Sky keeps dropping in and out".

I pointed out to the owner that, clever as the dish controller might be, there was no way it could track the satellite if the signal was being blocked every few seconds by buildings, trees or mountains. I recommended that he switch it off while the vehicle was in motion. He seemed to accept my explanation with some reluctance and drove off with the dish still making itself dizzy as it searched frantically for "the Sky". I just hope he will be a thousand miles away from me when the analogue "Sky" transmissions are switched off in favour of digital.

Nokia ACU5152

The installer who brought this dish positioner ("Antenna Control Unit") announced that it was "dead". In fact it wasn't dead because when I plugged it in, there was a ticking sound followed by a bang and smoke. Now it was dead!

The L6203 motor driver I.C. can go short-circuit so that was my first measurement. Sure enough, when I measured the diodes in the associated bridge circuit, they all showed zero resistance until I desoldered the motor driver, IA04. The diodes now measured OK so the I.C. was faulty. I couldn't see or measure any other faults, which was rather puzzling, so I put on my safety spectacles and applied power again. Nothing spectacular happened but the unit failed to light up. A quick probe with the meter indicated there was no 5 volt supply but the 20 volt supply on DP12 indicated 36 volts and the 40 volt supply on DP11 indicated 78 volts! I bet a broke a world record in plug-pulling!

Since there was no output from IA01, the 7805 regulator, I assumed it was dead and replaced it. A quick call to Genserve (yes, I paid my subscription) elicited the suggestion that the two small electrolytic capacitors in the power supply might be causing the high voltages. Replacing these proved the advice to be correct. A new L6203 I.C. finally got the unit working correctly.

Pace MSS300

The lady who called me for advice on her Pace receiver said that a BskyB adviser had diagnosed her problem cause as "the LSE in the LNB". Frankly, I'm surprised she hadn't been told to "wipe the card" as this seems to be standard advice for almost any fault. It amazes me what nonsense people believe. The symptom appeared to be a lack of horizontally polarised channels but an installer from many miles away had replaced the LNB, charged her for the pleasure, then announced that the receiver was faulty and there was nothing more he could do! He didn't even leave the old LNB behind!

I didn't witness the symptom myself because she didn't want to pay me for a call-out. Fair enough. Her son brought the receiver to my workshop and left it. As soon as I had time, I tested it. The power supply was whistling like a banshee and the pictures were obscured by horizontal streaks. Replacing all the capacitors (supplied in Relkit 9 from SatCure) cured these faults and the receiver was fine. The cause of the lack of horizontally polarised channels might have been interference from the power supply at around 25kHz. This has been known to switch a "Universal" LNB to "high band" and, if the installer doesn't have the knowledge to test for this by tuning to the lowest frequency, the diagnosis is easy to miss.