Sky Digibox
Sky Analogue


If you find this information useful and want to thank me, why not buy one of my low-cost "virtual books" that you can download direct to your computer? My books can be read on-screen or printed out on paper. They are full of colour photos and illustrations. Click on "Books", above, for more information.
Send this page address - CLICK HERE - to a friend !

NOTE: This analogue receiver is obsolete. Most accessories and modifications mentioned on this page are no longer available.


Return to satcure satellite contents Return to SatCure index page

Amstrad SRD700 - SR950 and "+" repairs, upgrades

Amstrad SRD700 sr950 receiver main board and videocrypt decoder board

SRD700, SR950+ and basic version SR950

SR950 has less menu options. It is designed for use ONLY with a 9.75 GHz LNB.

How do I fix a dead Receiver?

A Power Supply repair kit is available but make sure the PSU really is dead (no voltages) before ordering the kit! Order SATKIT 16

Amstrad SRD700 sr950 receiver power supply

Crackling on audio.

Adjust the Audio frequency for the affected channel(s) in the setup menu. If that fails to remove the crackling sound, the audio demodulator trimmers on the Tuner Board might need to be adjusted. The trimmers are VERY flimsy so use the correct plastic adjustment tool (you can make one from a plastic knitting needle).

The audio demod centres can be very roughly set-up as follows:-

a) Unplug the LNB.

b) Enter the audio mode and set to Mono, (tuning bar setting unimportant), Store settings, wait for OSD channel number to clear.

c) Listen with headphones to the stereo output of the decoder scart.

d) As accurately as possible, adjust RV3 such that it is positioned exactly half-way between the edges of the band of loud white noise. This roughly sets up the 10.70MHz centre.

c) Reconnect LNB. Select a channel with a known stereo audio track. e.g. MTV.

f) While still in mono, adjust the audio tuning bar for best sound.

g) Set to stereo, store settings.

h) As accurately as possible, adjust RV5 such that it is positioned half-way between the edges of the undistorted audio band. This roughly sets up the 10.52MHz centre.

i) Check the stereo audio on other channels. Should hear no distortion, pops or crackles and no sibilance on speech.

j) If possible, heat the tuner module with a hairdryer and ensure that the stereo audio remains in tune, if not repeat the process until the audio tuning remains stable.

What causes Sparkly/streaky pictures? (possibly getting better or worse as receiver warms up)

If not caused by dish/LNB/cable then it's usually a faulty tuner module.
A replacement tuner assembly is very expensive. Try removing it and replacing all electrolytic capacitors inside it. You can actually solder new capacitors on the top side and leave the old ones underneath. Usually only the 10uF capacitors cause problems.

Order Relkit 16

> Dear Martin, Before I sent you the e-mail regarding a SRD700 with
> the dodgy tuner, I called Amstrad technical. They advised me the
> fault was down to the tuner and a replacement would be around lbs50.
> I pointed out that there were a lot of capacitors in the tuner and
> wondered if they could have suffered like capacitors do in satellite
> receivers. The man on the other end replied "No, we now use higher
> quality capacitors in our receivers, although you could check two or
> three that, if gone, would affect the picture quality." He kindly
> faxed me a circuit diagram of the tuner enabling me to pin point
> which capacitor, if any, going faulty would result in this problem.
> After reading your e-mail I decided to check all of them. Yes, you
> guessed it, all 13 were faulty. I replaced them with ones of 105
> degrees rating (what a job that was!) and the receiver now works
> fine and is back at the customer's house. Thanking you ,Trevor...

>Dear Martin, many thanks for your help with my sparkly picture fault.
>The improvement after fitting your "Relkit 16" capacitors is huge and
>the picture is now perfect! Now, for just £80 and two people who have
>been very generous with their help, I have a complete system. Please
>find enclosed 2 books of 27p stamps. I hope they will help you to
>help others, as you helped me :o)

What causes no decoder messages with the card in or out?

  • Usually caused by incorrect SETUP.
  • Make sure that video bandwidth is set to NARROW or AUTO.
  • In basic version this is shown as follows: Narrow = (.) Wide = (...)

Also replace the 1uF capacitor which is next to the PTV111 chip on the decoder board.

>Dear Martin,
>I had troubles with my SRD700 receiver with sparkly video, slowly becaming
>worse week by week and when I decided to bring it back to an Amstrad repair
>center I discovered that Amstrad is not any more officially represented and
>supported here. I queried the Net for "Amstrad" looking for some reference
>about repair centers at least in Italy but I discovered that Amstrad itself
>seems not to exist as such any more! Looking around through Altavista query
>results I found your incredibly useful pages and I got crazy reading the
>SRD700 repair FAQ finding the exact description of the problem I was
>Soon I decided to spend some of my very limited spare time to put my hands
>on the receiver (now I am a serious 39 years old professional electronic
>designer, but I began playing with electronics when I was 14): I opened the
>SRD700, dismounted the RWTRX-1635 tuner and I was surprised by what a bad
>layout/thermal design was (consciously?) adopted by the RWT Ltd designers:
>all but 1 of the electrolytic caps (rated at 85 C) were mounted on the
>lower side of the tuner, which is accurately sealed on 4 sides such to
>avoid any air flow and operate as a perfect "caps oven"; 3 caps were indeed
>"well done" and so hardly stressed by the heat that the color of the
>plastic cover drifted from green to dark gray. I have also noted that the
>470uF cap used to bypass the 13-18V LNB power source was rated 16V (economy
>is important but reliability too...)!
>I substituted all the caps with high quality, high temp tantalum (<100uF)
>and electrolytic (>100uF) parts mounting them on component side such to
>avoid the oven effect, then I placed the 12V fan just on the
>left side of the tuner such to provide a minimal constant air flow; the fan
>is fed by the receiver 12V source through a series 5V-1W zener to obtain a
>reasonable compromise between air flow and fan speed/noise.
>I spent a couple of hours to complete the operation and now I have a fully
>operational receiver! I'd like to thank you a lot for your valuable
>"stampware" info which turned my mind to repair the SRD700 by myself. I
>can't send you unlicked (nor licked) english stamps, something else may be
>reasonable to show you my gratitude?
>Andrea Pugnaloni

Thanks, Andrea. Our fan kit includes a resistor to limit the fan noise but the zener diode sounds good to me! (See satkit page for details of the miniature fan kit).

Is there a Factory Reset?

There is NO factory reset but you can get the receiver to tune ALL channels in transponder order by activating the Autotune mode. Then you can press the "smiley" button to enter "favourites" mode and reset the channel order to suit your requirements. It is very tedious to do, however!

How does AutoTune work?

Press SETUP, > , >, >

Now the little box with three wavy lines will flash. You have 5 seconds to begin the Autotune sequence:

Press SETUP then MUTE (loudspeaker button).

Autotune will take several minutes tuning first the horizontal channels (even numbers) then the vertical channels (odd numbers). You can press CANCEL to stop it but you can't reverse the changes. The screen will display "OK" when Autotune is finished. Press any number to exit.

If AutoTune appears to work (you see pictures as it tunes) but the channels don't get stored (just "snow" when AutoTune has finished, then the EEprom is faulty*).

Stuck in standby

Usually a faulty EEprom* but try cleaning out the 40 pin microcontroller IC socket with Isopropyl alcohol. It's usually full of brown gooey flux!

*Faulty EEprom

The EEprom is usually damaged by connecting the TV Scart socket to certain models of TV set. Pins 10 and 12 of the Decoder scart are connected to the EEprom. It's best to disconnect them by snipping out resistors R95 and R96 (270R) on the main board.

A new blank EEprom will not work. You must fit a pre-programmed EEprom (SatCure can supply).

Can I fit a decoder socket instead of the plastic blanking piece?

Yes but you might need to fit a whole bunch of other components as well!

You will need the following parts:

C20, 26, 27, 29, 41 10uF
R38 100k
R55 10k
R53, 34 470R
R51 22k
R49, 50 270R
R52 15k
R46, 47 75R
R54 1k
L6, 7 wire link

IC4 MC14053
TR5, 15 2SC1740
TR6 2SA933
Clip-in Scart socket

You will also need the following if not already fitted:

C28, 24, 25 10uF
R37, 39, 42, 43 270R
R36, 44, 45 10k
R40, 41 1k
TR2, 3 2SC1740

For stereo audio output you will need:

Twin phono socket assembly
C21, 22 10uF

For a complete fault-finding guide, read "The Satellite Repair Manual" available from SatCure.

This information is given in good faith, based on several years of workshop experience involving thousands of repairs. No responsibility will be accepted for any death, damage or injury caused either directly or indirectly by the use of this information. The reader should check the facts himself. It is assumed and stressed that the reader will be familiar with good, safe, electronic workshop practice and will be familiar with all tools, components and terms used. If there is any doubt about the reader's ability to carry out such work competently and safely, the work should be referred to a specialist engineer.

End of FAQ


Return to satcure satellite contents Return to SatCure index page

Copyright ©1998 SatCure
Version 1.4 updated on October 17, 2000
This file may be downloaded for private and personal use but NO part of it may be published in any form without the prior permission of the author.

This Web Site was produced entirely on a Macintosh computer

Made with macintosh Send this page address - CLICK HERE - to a friend !