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Satellite Workshop 26

Jack Armstrong


Don't call me.....

Several people have phoned me at home, recently, having been given my number by Erm. If I catch him, I'll wring his neck.
I was just sitting down to my dinner when the telephone rang. A Plymouth number, according to the display. Thinking that it was my sister but inwardly cursing I picked up the handset and mumbled hello.
"Hi! I was given your number by erm... anyway I've got this Bush.."
"Sorry, I deal with satellite repairs. You want the Garden Centre."
"No, yes, that is Jack isn't it?"
"Ye-es," warily.
"Ah, good. I've got this Bush. A thirty five hundred I think. Same as a Pace six hundred.."
"Six thousand?"
"Bless you, I had a cold last week. Yes, it's an Ess Ess six hundred. Anyway, it's dead. You can get the kits, can't you?"
"It uses a transformer. It's not a switch mode supply!"
"Right, a transformer. How much?"
"Oh, well, I've got one in the workshop. You can have it for ten pounds. It's heavy you see."
"Ten pounds?"
"Includes carriage. Heavy you see. Long way to Plymouth."
"But I can get a second hand receiver just up the road for fifteen!"
I put the receiver down, abruptly, and returned to my dinner. He probably thought that was very rude of me. What I was about to suggest would have been more rude.

Ferguson SRD6

("Too much hot air")
Most mornings I nip out and have a cup of tea with Jerry at the local TV repair shop. Most of my business is with the trade so I can go for days without seeing a "real" customer and life gets lonely. Today, Jerry had a present for me: "An SRD6 from Tom" he beamed. "He'd like you to have a look at it." Tom repairs TVs and Videos but he works in the next town so Jerry and he get along just fine. They both give me their satellite receivers to fix, unless it's a simple power supply repair.
I took the SRD6 back to my workshop and connected it up. The pictures were rolling and jumping. There were no decoder messages and the pictures on the unencrypted channels looked dull as if the contrast had been turned down.
My first stop was the video level adjuster, PV01, close to the tuner module. I turned this anticlockwise quite a long way before the pictures stopped jumping. Decoder messages reappeared so I inserted my card. The picture was stable but very grainy with some "sparklies" and a herringbone pattern for good measure! Although the picture was watchable and many undiscerning customers would have been happy with it, I knew that this was not as Ferguson had intended. Besides, nobody had been inside with a screwdriver and the adjuster could not have slipped half a turn by itself!
I turned the adjustment back until the picture scrambled again then heated the area around the tuner with a hairdryer. This action restored decoder operation temporarily. I replaced a few electrolytics but without any improvement. Heating the underside of the board had a more marked effect so I decided that the faulty part might be a surface mount device.
Freezer spray and hairdryer confirmed my suspicions but I could not pinpoint the actual component. Then I had a brainwave.
My desoldering station is made by the American company called Pace (coincidence). It is very robust and effective (eat your heart out Weller owners!) One of the features I have never used is the ability to blow instead of suck. I cleaned out the glass reservoir then switched the iron to blow hot air. This could be directed very accurately and quickly located TV04, a BC858. This transistor is connected to the trimmer, PV01, which I took to be the video level adjuster. With TV04 replaced (I used a BC856B, the nearest PNP transistor in my workshop) the pictures were restored to their normal high quality. Tom will be pleased, or maybe not, since it's going to cost him half an hour's labour.


The Ferguson fault reminded me of a PRD 900 which I repaired last week. It arrived all the way from Manchester with the same symptoms. The owner had thought it was caused by the rain but, when the rain finally stopped and the symptoms remained,he decoded to send it to me.
I put it on test and watched the rolling pictures, bemused. Despite the help of the service manual, I couldn't trace the cause with my oscilloscope. Out came the hair dryer (what would I do without it? Use a towel, I suppose).
By directing the warm air at the capacitors around the tuner I was able to stop the picture from rolling.
"Easy!" I thought to myself. "One of these electrolytics. Be fixed in a jiffy."
It wasn't. An hour later I was directing my hair dryer at the same spot, with the same effect, having replaced all the capacitors in that area! Well, we all make mistakes. The cause was obvious when I realised that there was a large delay between directing the hot air at the board and seeing a visible effect. The faulty part was underneath the board! Q100, a surface mount transistor, was the only one in that area. A new FMMT2369A restored normal operation.


No less than four of these arrived by landrover from a retailer some miles away. He'd "done a deal" and swapped a Hitachi 21 inch for these "perfect working order" receivers. They looked perfect, but they didn't work.
My first problem was that none of them responded to thhe remote control. Then I realised I was holding an "MSS" remote instead of the "Prima RC-10" which looks identical!
The first receiver displayed "No Signal" on blue background. Audio was present if the channel tuning menu was selected (audio mutes with blue background). Close inspection immediately showed a dry joint on L305.
The second receiver showed similar symptoms but without any sound apart from a hiss. Changing channel, however, produced pictures and sound on a few channels. I found that the installation menu had been set for "single" LNB which seems to lock the LNB voltage to 18 volts. Selection of "Universal" restored normal operation.
The third receiver had no "E to E." In other words, it passed no terrestrial aerial signal at all. I've had lots of MSS100 with this problem and it's caused by static charge building up on the TV aerial and discharging through the TDA8275. In this case there must have been a big electrical storm nearby because the 39 input resistor was also open circuit.
The fourth Prima was "dead." It did not light up and there were no output voltages from the power supply. A new TOP202 device and an F1A fuse sorted that out. I think it was caused by a mains surge.

Amstrad SRD700

Occasionally these arrive at the workshop "dead" and all that is needed is a new fuse and a TOP202 device. The one brought in by Charlie, the butcher, was not so easy to fix.
After scraping off a layer of dripping, I discovered that the 200 volt avalanche diode had also failed. Unhelpfully, the circuit diagram lists this as a 5 Watt 300 volt diode! Luckily, SatCure stock the correct device which is supplied in their repair kit, so all was not lost.
Once the receiver was up and running, it exhibited more faults: occasionally the screen would go blank or the picture would disappear in a mass of sparklies or it would refuse to come out of standby. The cause of all these symptoms was flux in the microcontroller I.C. socket. I've come across this in SRD540 and similar models. A quick scrub with Isopropanol on a toothbrush restored this receiver to normal working. (My wife moaned, afterwards, that the toothpaste tasted bitter but I'm used to this sort of complaint now and simply smiled nicely).

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