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Return to SatCure index page HOW DO I PLACE AN ORDER? Amstrad SRD500/SRX300 Repair FAQ Dead. No voltages from power supply. Disconnect from the mains. Replace the 1.25A fuse on the power supply board. If this fails to cure the fault, remove the two securing screws and the two connector plugs and lift out the PSU board. Discharge the large capacitor by short circuiting its pins with a 10‡ resistor. If it discharges with a 'bang', R2 or R3 (120k) has failed open-circuit. Replace them both with 350 volt rated resistors. Replace C5 with 100µF/35v/105°C and C10 (10µF/50v). Now try the PSU again. If D8 (1N4148) or R9 (220‡) fails the output voltages will measure correctly with the output connector unplugged but will fall almost to zero under load. The same symptom is caused by C5 and C10 (above). If PSU 'ticks', disconnect L707 on main board. If receiver now lights up, replace tuner. The simplest way to fix any fault on this model is to fit our RELKIT4 which usually cures: Dead or display flashes briefly but receiver won't work Transformer ticks but receiver won't work No audio or some audio channels missing Blank screen or low video level until warm Various other symptoms Be sure to squirt the 4-pin power supply connector with WD-40 and work it up and down to clean it. Connect a voltmeter to the test pin marked "5 volt" on the decoder board and adjust the trimmer on the power supply board until the voltage is 5.0 volts (clockwise to reduce). WARNING! High voltages are present on the power supply! If RELKIT4 doesn't fix your "dead" receiver then fit the supplementary kit SATKIT4A as well. Using the SRD500 with a D2Mac decoder Inside the receiver, connect a wire between pins 3 and 7 on the D socket and also connect it to pin 8 on the Scart socket. Pins 3 and 7 are int/ext video/audio respectively but there is no automatic switching voltage. By applying the voltage from Scart pin 8 you will be able to press the TV/SAT button to switch the D2Mac decoder in or out. This is a bit crude so I'd be interested to hear of ideas for an automatic switching system! Idea supplied by Peter of Aligator Electronics, Gwynedd. The connections to the D-connector of the SRD500 are as below. There is no RGB. You would have to connect directly from the MAC decoder's output SCART socket to your TV to use RGB. Pin Function --- -------- 1 Audio input A (left) 2 Video input 3 Video INT/EXT control - Like pin 8 of a SCART socket 4 MAC baseband output 5 PAL baseband output (unfiltered/unclamped) 6 Audio input B (right) 7 Audio INT/EXT control - Like pin 8 of a SCART socket 8 Ground 9 (not used) 10 PAL video output (filtered/clamped) 11 Ground (shield) 12 Audio output A (left) 13 Audio output B (right) 14 (not used) 15 (not used) You may need to connect pins 3 and 7 of the D-connector to pin 8 of the MAC decoder's SCART socket. If you get MAC picture but no sound disconnect pin 7. Please also read the D2Mac page. Displays "Card Invalid" when card is inserted Dismantle the card slot unit and clean the switch cantacts at the rear. Amstrad SRD500 Channel Expander Control The Amstrad SRD500 can be modified to give a 12 volt output on certain channels. This output could control the Global Communications "ADX-plus" Channel Expander so that you can watch programmes from Astra's fourth satellite, "1D". The ADX can shift the entire band of frequencies 500MHz higher and, with the modification, will do this automatically for channels 40 through 48. A distinct improvement over manual operation of the ADX. Alternatively, the new 12 volt output could control a Global Communications 22kHz tone inserter which will select "High Band" on a "Universal" LNB. If you want to watch programmes from two satellite clusters (for example Astra and Eutelsat) the output could be connected to a Global Communications VH1-DC switching unit. Channels 40 to 48 were chosen. The only switching function which can readily be used on the SRD500 is the TV/SAT button. However, this selection can not be stored on a per-channel basis so to use channels 40 to 48 for the 12 volt output is ideal. The 12 volt supply is obtained from Link "JP164" at the front of the main board. The sketch of the SRD500 front panel board shows where to solder the three wires. Zero volts is point "1", Q152 centre leg is point "2" and IC151 pin 16 is point "3". The few components required cost very little and can easily be assembled onto a piece of "Veroboard" or similar. For a more detailed description, please refer to the original SRD400 modification article. A minor drawback of the system is that the ADX can switch on and off while you are tuning the receiver. To overcome this nuisance, disconnect the wire and switch the ADX toggle switch ON while tuning. Once the channels are tuned and stored, switch the ADX OFF, reconnect the control wire, and it will then be switched on automatically for channels 40 to 48 only. SRD500 front panel SRD500 modification circuit HOW DO I PLACE AN ORDER? For a complete fault-finding guide, read "The Satellite Repair Manual" edition 5 available from SatCure. DISCLAIMER 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. THIS FAQ IS NOT APPROVED BY SKY OR BY AMSTRAD End of FAQ Return to SatCure index page Copyright ©1996 SatCure Version 1.2 updated on January 10, 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 Send this page address - CLICK HERE - to a friend !