Readers` Corner 7-8-2001
Contents
1. fos PO Box 190 We can only answer questions or remarks of general interes years and published in Elektor Electronics In view of the amount of post and email received it is not possible to answer all correspondence and we are unable to respond or additional information about Elektor Electronics projects to our readers concerning projects not older than two o individual wishes and requests for modifications to Capacitor ESR Tester Dear Editor I have built this circuit from the article in your September 8002 issue and the instrument seems to work as described In the section about adjusting the instrument you say that an accurate voltage source of less than 200 mV is required for the adjustment of P5 However being a hobbyist on a limited budget I do not have access to precision test instru ments of the kind that s likely to supply or indeed measure such a voltage Can you indicate how I should proceed I was thinking along the lines of a low imped ance potential divider 100 ohms to 1 ohm I was hoping to use the ESR Tester to locate faulty capacitors in a number of valve radios I am in the process of restoring to their former glory M Faulkner An excellent idea use new technology to restore the old Leaky capacitors are a common source of problems in vintage radios Regarding the 200 mV est voltage your own sugges tion is usable in principle 0 2 V is obtained from 20 V by means2. of a 100 1 potential divider The divider may also be dimensioned or a higher impedance the aim is not so much a stable voltage but to get the LCD to indicate the same voltage as a reason ably accurate DVM Hard Disk Interface for the Printer Port Dear Editor when I run the program I2L4 exe mentioned in the article January 28008 under plain DOS I am treated to the following error message Parallel Port 0378 I2L adapter detected HDD xtor 82560A4 Error unsupported partition type Whatever type of hard disk I attempt to use the program detects the interface and the HD but the combination remains useless Am I missing something I think I have it all properly connected up F D Burgess 7 8 2003 Congratulations the interface you have built is working prop erly The problem is not the hard ware but the partitioning of the hard disk The DOS version of the driver is only capable of accessing disks using a FAT16 partition By contrast the Win dows version will happily talk to FAT32 disks as well Year Volume 2002 CD ROM Mr Finch of Aylesbury kindly advised us that at least two arti cles on the Elektor 2002 CD ROM could not be opened from the archive program In these cases a different article is opened The problem is caused by incor rect links in the article database However the relevant articles are contained on the CD ROM and may be opened using Acrobat Reader by selecting th
3. the Pier struck off By law the designers should have paperwork describing these prod ucts plus the owners will have some kind of user manual Should these products be banned and their designers and owners asked to file reasonable excuses we think not Mr Thomas replied I agree entirely I have a shelf of pilot s manuals and the address of the Houses of Parliament 113
4. 10 years in prison in the UK The UK Terrorism Act 2000 says Section 58 1 A person commits an offence if a he collects or makes a record of information of a kind likely to be use ful to a person committing or prepar ing an act of terrorism or b he possesses a document or record containing information of that kind 2 In this section record includes a photographic or electronic record 3 It is a defence for a person charged with an offence under this section to prove that he had a rea sonable excuse for his action or pos session 4 A person guilty of an offence under this section shall be liable a on conviction on indictment to imprisonment for a term not exceed ing 10 years to a fine or to both or b on summary conviction to impris onment for a term not exceeding six months to a fine not exceeding the statutory maximum or to both Clearly an accurate long term timer is invaluable to someone planting a bomb such as the one that blew up the Conservative Party conference in Brighton some years ago The reasonable excuse defence might be enough to get us all off of course M Thomas Thanks for the information we are indeed amused rather than impressed An interpretation of the law as suggested by you could equally be construed to apply to the makers and owners of Mechanical alarm clocks Batteries GSM phones Electricity A Tourist Map of Brighton with
5. e file n pro duction number pdf found in the folder Articles N on the CD ROM Crescendo Millennium Edition Dear Editor I have a query on the Crescendo Millennium Edition published in the April 2001 issue of your magazine I am measuring a direct voltage of 5 volts at the amplifier output In an attempt to eliminate this voltage I replaced the 28K792 by a 28K537 unfortu nately to no avail I now suspect that the problem is caused by the MJE340 and MJE350 Since the hpg specs of these two transistors are different I started to search for a matched pair I telephoned a number of suppliers only to be told I had to come up with a dif ferent type number before a matched pair could be ordered Do you have suitable type numbers for me M Kenyon It is by no means necessary to replace the MJE340 350 pair by other types With complementary transistors there is always a dif ference in their exact hFE speci fication In audio amplifiers that difference is typically compen sated by the overall feedback You need to look deeper into the circuit to find what s causing the Elektor Electronics offset voltage a likely source is major differences between the input transistors If you measure at the output of opamp IC1 very likely you will see almost the supply voltage of 20 V If so try better matched input transistors or modify the offset control lower R4 and R5 to 1 MQ and increase C3 to 330 nE The ampli
6. fier output should then sta bilise at 0 V USB Audio Codec Dear Editor congratulations on the publication of projects that can be connected to the USB bus these prove that Elektor is miles ahead of your competitor EPE which seems stuck somewhere in the late 1980 s as far as the tech nology of most of their projects is concerned I would like to build he USB Audio Codec December 2002 but modified with a coaxial S PDIF input Can I simply replace the TosLink input on the card by a cinch socket and a 75 Q termi nating resistor Also in view of this modification I would prefer to build the circuit on veroboard do you think that will work Finally a question about the copy bit I would like to use the card to copy a number of recordings on DCC cassette to CD using my PC Will I be able to transfer private recordings made using the ana logue input on my DCC player J Grymonprez No a 75 Q resistor only is not sufficient for the purpose You are referred to the article Opto to Coaxial Audio Converter published in the April 1997 issue There is no reason why the circuit would not work when built on veroboard provided the component placement does not differ too much from that on the PCB we designed The recording activities you describe should not cause problems Week Month Timer Dear Editor You will perhaps be amused to know that this article April 2003 potentially makes your readers liable to
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