Satellite Workshop 16
The local chip shop owner is Italian. He called me to complain that
the receiver I sold him four years ago had gone faulty "under
guarantee." Now, I don't know the legal situation in Rome but in
Britain the usual guarantee period is 12 months! Anyway, I agreed to
call on him to investigate and promised not to charge for the call
out.
"It's a verra pecooliar" he told me. "When I walk-a across-a da
floor-a da satellite she changes-a channel by herrself!" Now Mario
lives in an old thatched cottage and the floorboards creak as you
walk. Sure enough, as I approached the JSR3300 receiver, it changed
channel before my eyes!
I checked the external connections and removed the batteries from the
remote control but tapping the unit still produced erratic behaviour.
It had to be a workshop job.
Back on the bench I soon discovered that the connector plugs from the
front panel to the main board were no longer making good contact. A
squirt of switch cleaner on each plug soon cured the problem.
I earned myself a nice sack of potatoes!
I've had a GRD150 receiver in the workshop for seven weeks and it has
driven me almost to tears. The symptom was simply that, after a warm
up period of several hours, the decoder on-screen messages would
disappear and it would no longer unscramble the pictures.
I replaced every IC on the decoder board before realising that the
decoder was actually working but the ASIC was bypassing it and
feeding the still-scrambled signal directly to the output sockets. It
took several weeks to acquire the ASIC from Germany. I managed to
remove the suspect device from beneath the board by using a paint
stripper heat gun (I'm not recommending this method!) An hour later I
had soldered all 128 pins of the new one but it took another twenty
minutes to retouch the dry joints which initially prevented it from
working.
Anticipating success, I left the receiver on test while I had a nice
hot bath. Upon my return to the workshop, however, I found the darned
fault still remained. Finally, I traced the culprit by using freezer
spray and a hair dryer (she'll never know!)
A few more weeks passed before the new microcontroller kit arrived
from Germany, minus instructions. However, a quick call to a friendly
Grundig agent clarified matters and, five minutes later, the GRD150
was finally repaired.
I've repaired a number of Grundig receivers in the past. You need a
good working knowledge of the signal paths. Faults do occur in the
decoder ICs and, occasionally, the ASIC which handles most of the
video and audio routing. In fact this circuit is very similar to the
one used by Cambridge in the ARD200 (and clones made for BT, JVC et
al.) I've even seen a Grundig receiver which used an ASIC with a
Cambridge "ICCS" part number. Some faults are quite obscure. I had
one unit which occasionally gave a blank screen only on decoded
channels. The cause I traced to a faulty inductor, L11. Not something
you look for first of all! My GRD/Minerva Service Manual from Grove
Farm Publications (mentioned in a previous issue) has now paid for
itself several times over.
A customer posted me an MSS300 which displayed some intermittent
faults after about fifteen minutes warm-up time. The screen would
show a row of zeros in the top left corner, although the front panel
display was not affected. Sometimes a whistle could be heard from the
TV loudspeaker and sometimes the audio would disappear entirely.
I've seen similar problems on the MSS500 and they have usually been
caused by a bad connection in the microcontroller socket. However,
this MSS300 had a masked micro which was soldered to the board.
A call to Pace elicited the suggestion that the audio processor was
faulty (hence the sound problems) and was affecting the I2C bus,
thereby causing the incorrect graphics display. They were correct, of
course, as a new MSP3400 sound processor verified. Of course I knew
the answer all the time. I was just testing them.
A small number of ARD200 receivers seems to kill the series 10 Sky
card for no reason. The card might last for a week or two then show
the "Card Invalid" message. On one which I had in the workshop,
simply scraping the black spot off the card cured this intermittent
problem (not recommended by Sky). With others, however, the card
really is dead. Last week I received a call from a lady in distress.
Her fifth Sky card had been invalidated and she had been advised to
buy a new receiver. Could her ARD200 be repaired so it would not kill
the cards?
I agreed to have a look at the receiver which gave the correct
"Expired" message with an old series 07 card and an 08 card. It was
with some trepidation that I tried a new series 10 card but that
worked perfectly. The customer explained that a new card could last
for a week then fail without warning. Now I'm not a card "hacker" and
I know nothing about the inner workings of these cards but I tried an
experiment. The card receives a supply voltage of 5 volts when it is
inserted. There is also provision for increasing the supply to 12.5,
15 or 21 volts, under microprocessor control. However, the 15 and 21
volts lines don't seem to be needed so I inhibited them by soldering
together the base and emitter of both Q45 and Q46. These are surface
mount transistors which sit directly beneath the card. If the circuit
was switching these higher voltages to the card intermittently, this
would stop it. Only time will tell if this "cures" the problem. I
suspect that "pay per view" may no longer work and advised the
customer to save up for a new receiver.
Since the original Cambridge satellite company no longer exists,
there is no technical helpline for this product. The SVS200 is a
British Telecom "clone" of the ARD200 and I believe that BT spares
and technical information are held by Tele Aerial Satellite which is
now part of the SKY group. Unfortunately, it does not seem possible
to obtain any information about decoder faults so we are left
guessing.
Another receiver sold under the BT badge is the SVS300. I suspect
this is manufactured in China and is based on a design which has been
sold in Europe as the "Houston 1002". It is remarkably similar to
some Amstrad models. Recently, a power supply from one arrived in the
mail. Another dealer had attempted to fix this unit but without
success. Several repair kits had been tried but all resulted in loud
bangs. The cause was not hard to find. Someone had removed the
switching transistor complete with heatsink and copper land. On
replacing it they had failed to notice that the heatsink land is
required for continuity between two halves of the circuit.
I repaired the broken track and fitted another complete kit, in case
any of the components had been degraded by previous bangs. The supply
now tried to work but "ticked." It took ages to trace the fault to a
combination of faulty transformer and a shorted 2SB1143 inside the
little metal can.
When Astra 1D began transmissions it was possible to make a little
profit by selling Global "ADX" frequency convertors. All that changed
when SKY offered these units to subscribers for just 9.99. However,
we independents are left to sort out the ensuing problems since the
information leaflet supplied is not very comprehensive.
Last night I was having a quiet pint when my neighbour approached me
with an ADX in his hand.
"Do us a favour, Jack? Can't get this sod to work. Come across and
fix it fer us termorra?" With that, he plonked the unit into my hand
and left. I was so bemused that I accidentally paid for the
round!
This morning I got my own back by waking my neighbour at 8 am. His
receiver is a Pace SS9210. This is a two-input receiver and the tuner
uses IEC connectors instead of "F" connectors. I made a short adaptor
lead with CT100 coaxial cable, making sure that the IEC plug was
soldered. With a TV aerial you can get away with simply poking the
inner wire into the plug but an LNB requires current so the
connection must be good.
Once I'd demonstrated the working of the unit and explained that "Sky
Movies Gold" had to be tuned 500MHz higher than its listed frequency,
my neighbour was a happy man; so happy, in fact, that he gave me
50p.
Thank you, SKY. Without you I'd be out of business!
The following might be useful as a filler
A lot of my email comes from people asking about upgrades. Here is a
brief look at what is possible and what is not:
500 channels in an MSS500 or MSS1000 (as in the latest
versions with internal positioner). Upgrading is possible but a kit
is NOT available and is unlikely to be made available because of the
large number of variants. However, Pace might be able to upgrade your
receiver at their factory if it is a very recent model. Be sure to
tell them the complete serial number and model number if you
enquire.
Internal positioner in an MSS500 or MS1000 . This is not
available as a kit but you can send your receiver to Pace for
upgrade. (Not any longer. Pace stopped doing this).
Internal polariser board in MSS models . Not
available.
Internal 22kHz tone generator . Available from
SatCure.
Videocrypt AND Eurocrypt/D2Mac decoders inside one
receiver . Not available.
199 channels and a favourite channel menu. A kit is
available from SatCure to upgrade your PRD800. Not approved by
Pace.
J17 deemphasis with wide band audio . A kit from SatCure
improves distorted audio on foreign channels. Not approved by Pace.
Comes with comprehensive instructions but the J17 kit in particular
is not easy to fit, due to the number of fiddly surface mount
components required.
Enhanced menu options . This kit IS approved includes a
new microcontroller to give you a choice of LNB local oscillator
frequencies. Most tuners will cope but you might also need to buy a
2GHz tuner if you want the maximum tuning range.
External switch controlled by satellite number . A unit
is available from SFM Engineering (01407 742436) and apparently works
with any Pace model from the SS9000 onwards. You select a satellite
position number in each channel menu and the switch selects one of
five outputs. Some or all outputs can be used to control an LNB
switch, 22kHz tone generator, Christmas Tree lights or whatever!
Computer interface to control Pace receivers . Not
possible, however an interface with Windows software is available
from Kesh Electrics (013656-31449). This interface allows you to
download the channel information to your PC, rearrange it as you
wish, then upload it back to the receiver. It could be useful to a
dealer who wants customised programming for a batch of receivers but,
at £199, it's a little expensive for the home user.