Return to Amusing Stories page

Satellite Workshop 30

Jack Armstrong


Fidelity SR950

The model that replaced the Amstrad SRD545 is the SRD700 which is also badged as the Fidelity SR950 plus. The customer complained about "poor pictures" and she was right. When the channel was changed, the screen would remain blank for several seconds before a semblance of picture appeared. There were "sparklies" and "wavy lines" everywhere. In fact the closest description would be the effect you see on a video recorder when the tracking is wrong or the heads are worn. Scrambled channels remained stubbornly unwatchable. Some improvement occurred when I heated the tuner assembly with my hair dryer so I decided to tackle this first.
The tuner contains all the video and audio processing circuitry which employs surface mount devices and a few electrolytics that are hidden inside. The service manual includes a circuit diagram but, since there are no component designations on the tuner PCB, it is barely helpful. A new tuner costs more than fifty pounds so that wasn't an option!
With another non-working tuner to refer to, I was able to connect electrolytics in parallel with the existing ones, to see the effect, without desoldering the tuner from the board (a daunting task!). Soldering another 10 F across C41 created a dramatic improvement with "sparklies" disappearing to leave a reasonably crisp but dull picture. There were still no decoder messages and I could see that the video level was too low. Turning RV901 on the decoder board fully clockwise provided a temporary "cure" such that the decoder messages reappeared and I was able to get a Channel 5 TV picture and also Sky programmes with a card inserted. All encrypted pictures had horizontal white lines scattered across the centre two thirds of the screen. I got rid of these by connecting another 10 f across C68 on the tuner. Finally, I got the video level back up by connecting 10 f across C69.
Removing the tuner module is a tedious job, at best, and runs the risk of damaging tracks and pads. Consequently, I left my parallel capacitors in place and screwed the receiver back together with a sigh of relief. The capacitors don't look very tidy but they will probably last twice as long as the originals and it keeps the cost to a minimum for the customer.

Pace Apollo

The symptom reported was "No Signal" and that's exactly what I saw when I switched it on. Turning the blue screen generator off by pressing "F" then "Store" revealed a good picture which drifted aimlessly around the screen. The channel name, however, was nicely locked in the corner of the screen. Pictures from the VCR scart were perfect. This gave me a clue and I checked the circuit diagram. There were no sync pulses reaching the graphics generator I.C. This was not surprising since the PTV111 sync separator, U12, wasn't producing any!
I'm accustomed to seeing "no decoder messages" on this model, caused by the 1 F electrolytic C109. Replacing this had no effect, as I expected and nor did replacing X3, the 503kHz resonator. As it turned out the PTV111 itself was the culprit.
A different Apollo 120 exhibited very poor pictures resulting, apparently, from a very low video level. The dealer who brought it to me was tearing his hair out (he'll soon look like me!)
"I've replaced every component from the tuner onwards", he complained, "and still it won't work!"
"Oh", said I. "And did you check the power supply voltages?"
He stared blankly at me as if he'd never heard of such a thing. Funny how people miss the obvious. The 13 volt supply was far too low and replacing the reservoir capacitor, C73, immediately restored normal operation. While I had the receiver on the bench, I connected my Pace Link computer system and upgraded the Apollo to 250 channels. This is really of no benefit to the customer and Pace probably hate me for it but it gives me an excuse to charge the going rate. The dealer went away balder, wiser and several quid lighter in pocket.
By the way, if you can't afford the 199 Pace Link Pro system, there's now a Pace Link Lite available for just 99. This is model-specific and is sold by Kesh Electrics in County Fermanagh (013656) 31449. If you want to upgrade an Apollo 120 without this, you can get a 250 channel kit, a 22kHz tone kit and a reliability upgrade kit from SatCure, PO Box 12, Sandbach, CW11 1XA. Send two 26p stamps for details.

Pace MSS100/Prima

Following stormy weather, I've repaired quite a few receivers with "No terrestrial loop-through" or "No E-E" as they say in the trade. Grainy TV channels rule, OK!
The cause was not hard to find. Dust particles borne by the wind had deposited electrical charge on the TV aerial which had resulted in a high voltage surge at the input to the TDA8725T antenna signal processor I.C. in the RF modulator. Most MSS100 have a surface mount 39 resistor here which goes open-circuit but not before the chip dies. The Prima has a zero Ohm link which remains intact. Replacement of the surface mount TDA8275T is not difficult but I've wondered for a while if the input protection could be improved. Well it can: Pace recently issued a Technical Bulletin to describe a modification which removes "hum bars" that can be seen on terrestrial channels on some receivers. The modification also appears to improve the immunity to high voltage charge on the aerial. Obviously, it's impossible to protect against large surges or lightning but the addition of two components might help. These are: 913-0012501 a SMD inductor 1 2H 5% high SRF 230MHz and 912-0009951 a SMD diode BAV99 dual SOT-23 package.

(John, I have the diagram from Pace but the fax is too poor to reproduce. Maybe you can get them to post you a clean copy direct?)

Yesterday I had a different problem with an MSS100. It came through a chain of dealers and reached me with only the owner's fault description which said "no menus". I plugged in my Scart connector and mains cord. Sure enough, pressing "menu" on the remote made the LED flash but there were no menus. In fact there were no channel names either. I spent an interesting hour learning how the graphics generator worked. The sync pulses, data pulses, clock pulses and video input were fine, according to my oscilloscope. Strangely, the output vieo efinitely had the menu superimposed on it, so how could it disappear before reaching the scart socket?
The answer was simple. I had inadvertently plugged my lead into the VCR scart socket which takes its output before the graphics generator! Since the receiver worked fine all day, I can only assume that the customer fell into the same trap.

Parcel Farce

Now and again I receive units for repair by post. Occasionally these arrive intact but quite often they don't. People seem unable to accept that their precious receiver might travel beneath 100 mail sacks imposing a ton of weight upon it. I always recommend packing it in a box within a box.
Today I received a package which contained an SS9000 in its original "display box" but no outer packing. Sure enough, it had stickers on it announcing that it had been "resealed by.." a well known parcel carrier.
I repaired the cracked circuit board and replaced the faulty tuner with the kit then found the customer's letter and cheque which was dated 1996.
"Silly sod", I thought to myself and phoned the office number on the letter head.
"Sorry, Mr Smith left the company 18 months ago" said a puzzled voice. I was puzzled, too. The date on the letter was the same as that on the cheque. I can understand damage in transit but surely the parcel had not been on its way here for nearly two years? I looked at the date mark on the stamps.
Yes, it had!
Interestingly, another dealer mentioned that he'd had a similar problem. A receiver which he had returned to his customer in France had gone missing and he filled in the claims form. Two months later, the parcel company contacted him to say that the package had been found and would be returned to him.
"But I don't want it returned! My customer in France is still waiting."
"Sorry, sir, company policy. Lost and found parcels must be returned to sender. Oh, and there'll be an 18 charge for return carriage."