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Satellite Workshop 32


Pace PRD700

"What do you know about Mister Bishey, young lad? Owt or nowt?"
"Erm, sorry??"
"What? I'm a bit mutton-jeff like. Age, you know".
"I'm sorry, I don't know who you mean!" I shouted at the old fellow "and I'm definitely NOT YOUNG".
"No thanks, I had one afore I came owt. Anyhow, I don't have time for this. Could be dead termorra. Have a look at my Mister Bishey satellite decoder while I go and, um, rest me legs in t' pub. Ta."
He plonked a Mitsubishi ST-PB10 on the counter and hobbled out. This receiver is a Pace PRD700 except that Pace never sold it as their own brand, preferring to leave it to the likes of Mitsubishi and Granada to explain where the channel number display went (it doesn't have one).
It worried me that two screws were missing. Someone had been inside before me. Oh dear! The first thing I saw was a huge white ceramic resistor where R1 should be and another in the place of R8. These resistors are safety critical parts, designed to go open-circuit safely in the event of a fault. Some prize chump had decided to prevent them from doing this. Luckily, the damage had been minimised by a very black looking 6 Amp fuse! I fitted the correct resistors and an F1A fuse. The switching transistor was an under-rated plastic BUT11AF and stood "on tip-toes" instead of being pushed firmly down to make a good mechanical joint before soldering. I decided to replace the whole kit rather than try to fault-find.
"Zap za zap!" This was the sound of R8, R14 and the fuse going rapidly open circuit as I reconnected mains power. I wasn't giving up easily. The cause of the problem was a broken track to C8. I repaired this with Teflon-coated wire and tried again. This time the power supply ticked in time with the Standby LED flashing. Hastily, I pulled the plug. Something else I had missed! Well, I won't bore you with the details nor the number of cups of tea it took to trace the fault. C4, a 1n2F surface mount capacitor was cracked in half. The crack was invisible until I touched C4 with my iron. Since it's the timing capacitor for the switch mode I.C., it's hardly surprising that the circuit was ticking!
All I had to do now was to find two Pace screws black-japanned 3mm cross-head taptite sems - and reassemble the receiver before the elderly gent decided his legs had had sufficient rest (or beer, more likely!)

Pace PRD800

I've been taken to task by a reader!
"My PRD800 has too high an LNB voltage so I can't get verticals and the picture's dreadful and you haven't written about this fault!"
Well, I confess that I have never mentioned this particular symptom. The reason is that I always replace C5, C7 and C8 before applying mains power to a customer's PRD receiver and I assumed all other repairers did so, too. The reason is quite simple: C5 can cause ALL the power supply output voltages to go high if its capacitance value drops. So not only the LNB voltage goes high, but the 5 volt supply also goes to about 6 volts and starts to destroy I.C.s fairly rapidly. C7 and C8 simply cause the power supply to go bang! My advice to the reader was to disconnect the power immediately and to fit all of the capacitors in RELKIT1 before reconnecting. You can order reliability kits for various models from SatCure (Email: and I have mentioned this previously!

It's All Greek to me!

With the seemingly continual changing of Greece and Cyprus channels, some installers have become increasingly confused by the whole business of getting as many English and Greek stations as possible. At one point you had to have three separate LNBs on a 1 metre dish! At least one station is transmitting in the "high band" above 12 GHz.
An installer came to me with his problem. He had been using a combination of Universal LNB, Enhanced LNB and Standard LNB, together with a Global ADX and a Global tone inserter! (Please don't ask me how it all worked).
His problem was that he had carried out several installations with this mixture of parts but the one at our local chip shop had not worked. The 22kHz tone-operated switch was not letting the tone through to switch the Universal LNB to high band.
After a number of phone calls, we discovered that all 22kHz tone switches (unless specially ordered) prevent the tone signal from going through the switch to the LNB except a few that might have escaped the factory with bad connections on the relevant capacitor. This particular installer had apparently been using faulty units until now. The new batch was not faulty - but no longer worked as far as he was concerned!
Anyway, the answer is: If you want tone to reach the LNB, open the tone switch metal box and locate the small (and only) capacitor) that is hanging over the edge of the board and simply cut it off. If you do not want the tone to pass, make sure this capacitor is soldered firmly in place!
Grateful thanks to Mike Hancox of "Satellite Scene" who came and solved this problem. If you are Greek and want to watch Greece or Cyprus transmissions then Mike will happily install your system.

Pace SS9000

This old 60 channel dog came from a local TV repairer with the fault report "Blank screen with what looks like 'flyback lines' on it".
I checked it and the picture was OK (flickering of course) from decoder scart but every other output gave a blank raster. The "flyback lines" were caused by the TV losing sync through lack of a proper PAL signal. With my old 20MHz oscilloscope, I quickly traced the problem to U21, the video amplifier. VERY unusual. Luckily, it's so unusual for this chip to fail that I have dozens on scrap boards and finding a replacement was no problem.

Pace D100

I seldom see D2Mac decoders and, when I do, I prefer to pass them on to someone like Ian at Satfix in Swansea, since he understands them! However "PSU ticking" was the fault report on this particular one. I suspected the power supply capacitors and didn't want a loud bang when I applied mains power so I used my Capacitor Wizard to check the capacitors in situ.
C142 22uF, C144 and C145 10uF all showed a high ESR of more than 10 Ohms - clearly unacceptable! I checked all the large electrolytics on the secondary side of the transformer but these were less than 1 Ohm so I left them alone. Once the small electrolytics had been replaced with shiny new 105 C types, the D100 gave perfect pictures in conjunction with my old "test bed" receiver - an SS9200 - with the dish aligned on 0.8 degrees west of south.