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Satellite Workshop 50

Jack Armstrong

Pace SS9200

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.

Pace Prima

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 used.


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 bar"!


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 SatCure).

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 cost!
"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 service?
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 charges."
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.

E-mail blues!
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, either".

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 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).

Circuit Design
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 group).