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Satellite Workshop 50
It's strange how you can see none for months and then two arrive on
the same day! The first one had "dead" and "intermittent scrambling"
scribbled across it. In fact it wasn't dead but the Timer and "On"
LEDs were both permanently lit, which no amount of button-pushing
would change. I thought at first that the 2200uF electrolytic on the
5 volt supply might have failed but it was new, having been replaced
together with the rest of "Relkit 2" some months previously. I
replaced the EEprom but that made no difference. It HAD to be
something preventing the microcontroller from working so I checked
the 5.625 crystal and that was fine. Finally, I replaced the micro
itself and that cured that fault.
However, the picture was intermittent and would appear and disappear
when the unit was tapped. I traced the cause to broken solder joints
on the 10-pin decoder board connector.
The second unit had a similar symptom but this time the Timer and
Standby LEDs were lit. I checked the 5.625 MHz crystal, X10, and
there was no sign of oscillation. Replacing the crystal effected a
simple cure. I thought that it was too much of a coincidence to have
TWO faulty microcontrollers! Now the receiver worked OK but the
decoded pictures were very streaky so I spent a few more minutes
fitting Relkit 2 which includes several capacitors and a couple of
transistors. The result was perfect pictures.
A local TV shop proprietor brought this unit for repair.
"It goes dead after 5 minutes", he told me.
I left it on test for several hours but it refused to die. Inside, it
was in a bit of a mess. Somebody had clearly tried to fix this
intermittent fault and had resoldered every joint in the power
supply. A pity they couldn't have used some flux! Somebody had also
smashed the channel up/down buttons. I replaced these and tidied up
the soldering and the receiver still worked perfectly. As the TV
shop's customer was desperate to have the unit returned, I simply
swapped the mother board with one I had in stock and gave the
receiver back. The following day when I plugged the old board in for
more tests, it refused to light up! The power supply was pulsing and
occasionally the standby LED would light then go out again after a
few seconds. I had tested all measurable components and added
heatsink compound to the TOP201 without success. However, on a hunch,
I replaced the TOP201 with the slightly better rated TOP224 and that
provided a complete cure. Early units used the TOP201 but I suspect
it is slightly under rated - especially if heatsink compound is not
I had repaired this receiver previously when the symptom had been "no
decoder messages". On that occasion RELKIT 17 had provided a cure.
This time it arrived with a note that announced: "It won't lock and
gives strange messages".
Occasionally I get fault reports that make the mind boggle. Mine was
boggling right now. I connected the receiver on the test bench and it
produced a humming sound with the audio and a hum bar that travelled
repeatedly up the picture.
"Diodes!", I grunted, gleefully and began to remove the screws. Two
minutes later I was less cheerful. Apparently I had already replaced
the two rectifier diodes at the rear right corner. These are
notorious for failing and I had fitted BYV95A diodes as a precaution.
Replacing the remaining diodes made no difference to the symptoms.
Nor did replacing the large electrolytics. Feeling somewhat desperate
I replaced the 6 volt regulator. Aha! That eliminated the humming
sound, but the horizontal bar still scrolled up the screen.
I won't tell you how many parts I replaced before deciding that the
fault did not lie in the power supply after all. Removing the decoder
board made the "hum bar" much more pronounced. It was very odd and I
decided that the fault lay in the early stages of the video
amplifier. Heat made the problem worse, so that indicated a faulty
semiconductor, rather than a faulty capacitor. Freezer spray
apparently narrowed down the cause to transistor Q106 which adjusts
the video level. I was unconvinced and replacing this 2SC1815 had no
affect whatsoever. However, freezing it made the fault disappear.
Since I had already spent far more time on this than it warranted, I
tried soldering a 1k resistor from collector to emitter. The "hum
bar" disappeared, so I screwed the receiver back together with a sigh
of relief. I know that this "bodge" was simply masking a fault caused
by an associated component but it was 11pm and I was past caring!
Unfortunately, the unit "bounced" back a week later with the cryptic
note "No Sky Sports 2 or Discovery!" I tested it and the channels
were there but most of the horizontally polarised ones gave no
decoder messages! Now, one of the many parts I had replaced was
VR101, the video gain potentiometer. I had no 2k pots in stock so I
put in a 1k which seemed fine - certainly better than the mangled
thing left by a previous owner! However, the video level was a
fraction too low for the decoder's liking. I fitted a 4k7 and made a
mental note to order some 2k2 pots. Now the decoder operation was
fine but that original "hum bar" had returned in the guise of a faint
row of dots that floated up the screen twice a second. I decided to
fix it properly so out came the 1k "bodge" and in went the
oscilloscope. The cause was immediately apparent as I could see a
pulse coming out of pin 39 of the microcontroller U201. It shouldn't
do that! Swapping the micro for one from a scrap receiver finally
provided a cure. Strange that a micro could cause an apparent "hum
This receiver is almost identical to the SVS250 and the only obvious
difference is that it can store a few more channels. However, copying
the EEprom contents into a blank one and soldering that into an
SVS250 gives an instant upgrade. (Pre-programmed EEprom Stocked by
The tall gentleman in a grey suit who brought this one in for repair
wasn't interested in upgrading and didn't even seem to mind about the
"Sentimental value," he explained. "Left to me in a will. Never been
used and now it won't work. Just dots on the front."
He pointed to the front panel which displayed three horizontal LED
segments when I connected mains power. Pressing the "up" button
repeatedly resulted in the channel numbers changing in a normal
fashion but the three LED segments remained lit and there was no
picture or sound - just "snow" on the TV screen. This was hardly
surprising as my meter indicated no LNB supply voltage.
"Leave it with me," I said, with what I hoped was a reassuring grin.
The man in the grey suit looked very sorrowful and trudged out
towards his tiny foreign car. It never ceases to amaze me that a six
foot tall man will choose to drive a tiny 500cc vehicle - or perhaps
he had borrowed his wife's car while his Mundaneo was in for a
The SVS260 cover screws were loose - worryingly loose for a receiver
which had "never been touched". Close inspection inside revealed that
the heat sink screws were extremely loose and the tuner "F"
connection was held in place only by virtue of the plastic base
moulding. However, I was relieved to find that, despite the obvious
hammer work, there was no sign of any soldering. All the original
components were present, correct and "done to a turn".
The tuner module looked as if it could be salvaged but, to save time,
I simply removed a working unit from another scrap receiver which
some cowboy had "repaired" in the past. The three LED segments
indicated a problem with the 24C08 memory chip so I put a new one
into my Crownhill Associates Ltd EEprom programmer and loaded up the
contents from my PC. (Whenever I have a working receiver in my
workshop, I copy its EEprom contents onto my Hard Drive for future
use. I'd be interested to know if anyone has a similar "library" of
TV EEprom files?)
With these items replaced, the receiver now worked nicely, except
that the Sky programmes remained scrambled and there were no decoder
messages. Another twenty minutes spent fitting the capacitors from
"Relkit 17" sorted out that problem.
When the tall gentleman in the grey suit returned in his little car
the next day, I told him the good news. On hearing the cost he didn't
scream "HOW MUCH!??" as most customers do. Instead, he merely reached
for his wallet and commented on the weather.
"Bet you'll be glad when your own car is fixed," I said, placing my
foot well and truly 'in it'.
"Nothing wrong with it," he replied, looking a little bemused.
"Served me well these past ten years. Does 50 miles to the gallon.
Just as well, really, otherwise I couldn't afford your exorbitant
Before I could reply, he was out of the door and folding himself back
into the little vehicle. I'm sure the roof bulged upwards.
"Putt putt putt grrk," went the little car, crossly, looking for a
gear; any gear.
I received an e-mail message, today, from foreign parts and I'm still
not sure if the sender was serious. The Subject heading was "I can't
be bothered to read it" and the message said:
"Hi, I'm in (foreign country) and I want to receive programmes from
(name of satellite). I have attached a list of dish sizes and
locations so you can tell me what size dish I need, as I can't be
bothered to read it."
I smiled to myself and typed: "Sorry, I can't be bothered,
Subscribers will have noticed that my contact address is no longer an
e-mail address but a web page URL. The reason is that I often switch
off one address and use another in order to reduce junk mail.
Unfortunately, it means that genuine readers can't easily contact me.
To combat that, type the URL http://www.ukstay.com/jack into the
"Address" line of your Internet Browser. Press "Return" and my page
will appear on your screen. Now you can read the latest instructions
for contacting me. You can also find on-line "Frequently Asked
Questions" and answers about satellite faults so you might not even
need to contact me.
Even if you don't have a problem, you might like to look at my web
site and peruse the information about Hobby Electronics, Audio,
Satellite TV, etc. (Everything from a crystal set design to Chris
Muriel's explanation of Digital Satellite TV).
Many readers occasionally design simple electronic circuits and need
a way to draw them quickly and easily. Recently, I downloaded an
excellent software application to do just that! It is called
"DesignWorks Lite v4.0" and is available for both Macintosh and
Windows P.C.s from Capilano Computing's web site at:
The demonstration version will work for three weeks - long enough for
you to decide whether it is worth paying the 25 registration fee! I
have been using the "Lite" version for a couple of weeks and it has
been a Godsend, since I do quite a lot of circuit design. It comes
with a library of symbols (American) but it's easy to create your own
additional symbols if required.
There is also a "professional" version which supports lots of other
features including "SPICE" models (nothing to do with that pop