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Barry is an electrician with a rather cavalier attitude towards
safety and a somewhat simplified view of science. His Amstrad
receiver appeared to be well cooked.
"You've had this in an oven!"
"Nah, but I kep' 'im covered up all right. Heat needs oxygen t' burn an' 'em 'en't 'avin none o' tha'.
I refrained from pursuing this subject and told him to leave his receiver with me. Barry toddled off to replace Mrs Jenkins' fuse. He made his own by cutting four inch nails into pieces.
"My fuses is cheap an' 'em never melt" he had once pointed out to me. I couldn't argue with his logic. While I was thinking about it, I removed the top from his receiver plug, removed the roll of aluminium foil and fitted a 3 Amp fuse for my own peace of mind.
The SRD520 had distorted right channel audio which caused distortion on RF output audio, too, since left and right are mixed before entering the RF modulator. It took me nearly an hour to trace the cause of the fault to R89 (15k) which is connected to TR21 behind the sync-separator board. The resistor was open circuit and hidden under black glue.
The note on this British Telecom badge receiver said "DEAD" and, indeed it was. However, this was not surprising because some idiot had replaced the 4R7 and two 2R2 fusible resistors with 47k high voltage types! The 10R 5 Watt ceramic resistor was open circuit. That wasn't surprising, either, because the plastic-body switching transistor had been replaced with a metal-tag BUT11A, bolted firmly to the metal heat sink.
I replaced the 10R/5W ceramic resistor and fitted all the parts from SATKIT 17, including the BUT11AF, the optocoupler and the TL431 variable zener. Measurement of the other primary-side components revealed no other problems so I connected mains power and was rewarded with perfect operation.
This was somewhat surprising since the decoder often fails in this model and requires the fitting of RELKIT 17 to get it working again.
While I remember, look out for a batch of BUT11A transistors marked "932" which have been in circulation since early 1997. They are not correctly rated and cause switch mode power supplies to erupt in an often spectacular explosion. If you have any in stock or receive any in a future order, return them to the supplier with a copy of this article.
I'm a great fan of the Internet, as you may have noticed. Web Site
order forms are becoming common and often provide a quick and easy
way to place an order. Some firms even offer a discount if you use
their web site order form because it allows them to automate the
One major supplier advertised a discount "if you order via the Internet". Unfortunately, this description was too broad since orders sent by e-mail also fulfil the "via the Internet" requirement but require human intervention in the invoicing process. Consequently the discount was refused for e-mail orders. One wonders how this would stand up in court! Unfortunately, the order form system refused to accept certain order codes, despite the fact that these parts were listed on the computer (as confirmed by telephone). Promises to "ring back shortly" to sort out this problem were not fulfilled and orders were eventually faxed in the usual way to avoid further delays.
Another problem (common with many "professional" web sites) was the excessive use of pictures which create long delays before the order form can be displayed on the screen. Luckily I had previously had excellent service from this company, otherwise I might have gone elsewhere.
Many smaller companies such as Telepart (www.telepart.co.uk) and SatCure (www.netcentral.co.uk/satcure) provide easy to use order forms which list the available spares and appear on screen without excessive delay.
A lot of repairers still ignore the advantages offered by the Internet. Nowadays there is little excuse since a suitable computer or "Internet set top box" (www.satelliteuk.com) can be bought quite cheaply and used for other purposes as well. Internet connection can be free and even the cost of the telephone call can be eliminated if you agree to accept a few adverts each week (www.freecall-uk.com). The advantages include the availability of free technical help from manufacturers and like-minded repairers worldwide (contact email@example.com) as well as the possibility of discount on orders.
Finally, I must mention that my e-mail address is now "firstname.lastname@example.org". I change it from time to time to eliminate the build up of "junk mail" (one of the disadvantages!) Also, it ensures that those people who buy "Television" on a casual basis do not continue to receive free help for very long! (The old address will continue to work for a few more weeks for the benefit of overseas readers who have to wait longer for their favourite magazine!)
Another receiver from the British Telecom stable, the SVS260 is made by "The Orient Power Video Manufacturing Company Ltd." based in Kowloon, Hong Kong. I actually found their Internet web site by using the "Sherlock" search system on my Apple Macintosh computer. Unfortunately, they did not reply to my e-mail message so we are still lacking service information, apart from the booklet from SatCure.
This receiver came in with a complaint of "humming". I thought that might refer to a buzzing noise from the transformer laminations (yes, no nasty SMPSU) but it was silent. The audio from the TV speaker was perfect so I left the receiver to "soak" for a few hours.
When I returned to it there was a loud hum coming from the TV speaker on every channel. On a hunch, I squirted the large electrolytics with freezer spray. This had no effect until the spray hit the rectifier diodes behind the capacitors. The noise vanished instantly. Replacing diodes (D405, D406) at the rear right corner of the lower Printed Circuit Board provided a permanent cure. The diodes are black with a silver or white stripe (indicates cathode end). I replace these diodes with fast soft recovery type BYV95A which use glass bead construction.
I had a telephone call from Wossname up Church Street about an Amstrad SRD700. This is identical to the Fidelity SR950+ and uses a different power supply and main board from that employed by earlier models.
"What's the transistor that's soldered underneath the power supply?"
"It's not a transistor, it's a TOP202 integrated circuit."
"Ah, OK, I'll see if I can order one." Click. The line went dead before I could volunteer the SATKIT 16 that I had in stock.
A week later he brought me the offending receiver.
"No joy. Have a look at it for me, there's a good chap. I'll just be at "The Swan." You can buy me a drink when you've fixed it!"
I muttered under my breath and took the receiver to the workshop. Thje screws took no time to remove because, as usual, he had lost them. The power supply actually tried to work but the front panel LED was flickering, as was the blank raster on the TV screen. I removed the power supply. He had actually made quite a neat job of the repair, although I felt that he'd been over generous with solder on the TOP202. Hopefully he hadn't destroyed it with the heat!
A working power supply from another receiver produced pictures and sound so I investigated his power supply further. It appeared that he had used 85 degree capacitors (OK for now) and had not replaced the optocoupler or the TL431 adjustable zener (judging from the lack of black treacle around the pins). I replaced both components and the power supply sprang to life. For reliability I replaced the capacitors with high temperature types and also those in the tuner module (as supplied in RELKIT 16) since the decoded pictures were very "streaky". The "Lion and Swan" now seemed very inviting. I hoped Wossname had brought his wallet.