mvs sarma

Hi, Nice analysis AN920. Fine i shall be using your suggestions . Nice of you and thanks for a timely coincidental help. Regrads Sarma

Hi AN920, Thanks for such nice review and critical observations. In fact i have made the PCBs locally and just abt to assemble. -your comments are just useful. the 47pF cap across collector and base of darlington , if it could be shifted to base to earth of the same device, will it suffice without need to discretizuing the darlington? please comment. Sarma

Hi please see this site http://website.lineone.net/~harrison.elec/manuals.htm Sarma

Hi Walid jee, So Nice that you have taken my thoughts to 1960s- when we just entered Telecom service and were undergoing training- we has chance to get library access to see latest MAGs like Practical Electronics, Popuplar Electronics, Wireless Worls, It is Nice to see Practical Electronics kicking well evenafter 45 years. we used to get periodicals like ETI autralia, Electronics Autralia, On the communications front a munufacturer Eenkurt used to publish and distribute free monthly issues under the name 'Lenkurt Demodulator' an informative and small booklet covering various topics. Now a days you also see mags like Circuit Cellar, EPE Mag, Elektor-electronics, most being a mix of Software & Hardware Thanks agaian Sarma

Hi Thomas, Nice outcome for the effort put in, Siiting here in India, I really love it. All the best and wish you best future in your personal professional life Sarma

please see the photo whether RX 5030 tallies Sarma at Hyderabad

On the PCB or somewhere you are likely to find model number- otherwise, a set of radio and tape recorder circuit books are sold by M/s BPB in india and they used to have a shop in MG rad Bangalore. alternately, the local Panasonic service centre at bangalore(bangaluru now) can perhaps handle the item for you Atleat you might put a photo how the item looks like to be able to know its model number. Sarma

Hi, As some one said, enter the dragon may be easy, but managae and retreat is and will be a problem Same will be the case with philipsTV Evenif i could tell you how to enter , you require the data for seeting things over there-- any disturbance- you may not be able to work the TV to what it is a moment back-- So i suggest to try and get service manual for the set you hold. and thereafter things will be better and you may go ahead confidently Sarma

The programs won't generally draw PCBs-- we the humans use the program to help drawing the PCB layouts. Even auto routing will disappoint unless the components are intelligently placed. as a beginner you may find it hard-- it was hard to take food even unless parents taught us-- put little more interest and you would enjoy-- also try PCB123 software- it is free download - you may google for it. and the firm will be happily giving you finished boards if you forward the layout to them at some nominal price. All the best Sarma

Hi Walid, i have a doubt on the schematic put up- there has to be another transformer to recover the 455Khz IF after the osc coil.-- in fact the primaries of Osc coil and part winding of 1Sst IF (yellow Generally) wiil be in series. the secondary of this yellow device will give you 455KHz-- other calculations you are discussing with AN920 , i shall be watching curiously Sir, regards Sarma

Why to feel like thaat/ general priciple in outsourceing is not to get bogged by repititive work-- you can always take up a front end researchand comeforward with newre and latest designs-- you may revise old sesigns to be cost effective-- one has perhaps to be resourceful in his/her thoughts ang life is always encouraging-- Once you feel awalk of life is getting blocked , we can imagine that yet another new door is opning up for electronics of for that matter any curriculum. Sarma

Ofcourse, ther is another way- if you don'et want to use 5V at all the principal controll circuit regulating 5V, can be modded to control 12V instead of 5V. then the artifivial load on 5V can be avoided. Sarma

you use a break type jack --when you unplg the adapter (wallwart at 4.5V DC), the internal batteries should connect thro the contact. this techniques is used to cut off your speaker when you plug earphones.of course it is on audio output. same phylosophy can be follwed atinput supply also. Sarma

Hi Shamim, i fear you won't get -- you may have to purchase. I remember at Chennai- book shops in electronics spares market sell diagrams in multicolor. for eg.eletek books and kits is one source at chennai.

Hi, try here for alphaneumeric codes. http://www.tkb-4u.com/code/smdcode/indexsmdcode.php reg color codes, i feel normal codes do work with smd even if used however, the manufacturer concered can be googled for specific needs Sarma

Please accept the truth-- any malfunctioning equipment -- need not be electronics or computer related-- CAN BURN A HOUSE DOWN-- FOR EXAMPLE GAS STOVE WITH LEAKING HOSE or with a forgotten open valve STOCKED ETHENOL OR PETROL IN NON-STANDARD FASION UNCHECKED ELECTRICALL HEAVY DUTY SOCKETS AND APPLIANCES HALFBURNT RAGS LEFTOVER.... THE LIST IS ENDLESS. a bottle with alcahol leftover we do require caution Sarma

It is OK. do you find regulators inside or voltage stabilisation using zenor diodes? f so what is / are the regulator(s) / zenors used? Incidentally you never indicated the make and model Number of the equipment under reference. perhaps a replacement Tranformer is much cheaper compared to total equipment -- unless the said equipment is very much old-- then better to change-- while so, better go for modern 5.1 audio systems and try covert all your casttes to CDs progressively. Sarma

Basically you may have to study the other circuitry and the audio eqpt specification from the user manual. 1. whether input is 230 or 110V-- depends on your location. 2. you have two options. a. get it wound as it is by a local winding shop/repairer. b. do it yourself. If option is (b) , you have to count the secondary and primary turns while ripping it and Try to duplicate. If you know the seconday voltage, as per the electrolytics, i cold feel that secondary may be 15 to 18V or 20V at the wiorst. But you can't take chances, lest you may end uploosing other parts. By any means , it appears to judst duplicate it by careful reverse engineering. Even if the primary is partly burnt, at one place the wires may be jammed, it is still possible to be able to count the turns while ripping. FInally, if the make is known, transact with the manufacturer and seek a replacement transformer or the tranformewr data- Some times if you have a service data you may know the unregulated dc a\oltage and even the secondary AC voltage. if so you could improvisea substitute for it. All the best. Sarma

Hi, Why not try ULN2003 or ULN 2803 interface chips instead of discrete transistors. Sarma

Case.1 You try TRIAC control on primary with ofcourse suitable line filteres to meet local regulatory needs. then see that the output is stepped down to 12V. I feel this concept should serve your needs. Case2: you try to have halfwave rectification and try to regulate with nominal filter. then the output voltage should fall down. this time you may neeed higher power diode to supply larger average current in the absence of second halfwave. Case3: ypu go for non isolated dc-dc converter to convert the rectified 19VAc (may be around (1.4.14*19V)-2*diode drop as the supply is already isolated you dont need another transformer. a high current Frerrite inductor will do. Sarma

perhaps one may not call it smps, but Triac (primary comtolled) AC-DCconvertes are not unpopular. may be the type of technology was used for battery charging. Sarma

Hi Danny, Now adays experts of your status, should, ifeel, not confine to a cornerof software-- for example, i know of my co-brother whis a doctorate in chemical technology and equally good in electronic software and even hardware. Medical professionals are practicing not only medicine but also electronics to make their analysis and test procedures simpler. As a pasttime , i sincerely feel thaT YOU MAY BE ENTHUSED TO REALIZE YOUR IDEAS IN 3dBY YOURSELF AND I AM SURE , YOU WILL BE DERIVING GREATER SATISFACTION. nOW A DAYS IT IS NOT DIFFICULT TO FIND A INSTITUTIONknoWN TO YOU WHERE THE students are craving to do projects. you could perhaps be a guide to them and it serves dual purpose. Sarma

Aniruddha may appreciate that auto routing is NOT that effective unless the placement is opimum and the the software is really a wothy type. But again such items are obviouly priced HIGH and perhaps only High volue users and Idustries only can afford. One must accept that there is nothing to beat HUMAN BRAIN. Asd such we should leave the dream for auto routing (efective) be done with semi auto and manual methods.

you didn't mention how much current you want to draw at 5V --neither you mentioned whether it is DC or AC-- i if Dc you want large currents use 7805 with adequate Hestsink. if dc and for very small currents like less than 5 mA use a high watt (2watts)resistor of say220 ohms and a 2 watt zenor diode of 5 V or 5.1V (generally available if it is AC power you have to adopt different techniques. Sarma