SM2GXN

Very welcome to our forum/company MIC20, please read posts above everything is in there!!

Hi hat! logan_dslasher posted the link where you can download the book just above your post. Good luck! ;)

Hi Xenobius! I'm real curious ;D sounds like you are dealing with high power, what are you doing? What is the frequency, mains or higher and what is the maximum power the dummy load have to withstand?

There must be something I've missed ??? Where did you get 3,5 Amps? mrgjc I would really want to get hold of that formula you used to calculate those 3,5A ;)

That was real interesting, searched on google for "Hall-Effect Sensors measure dc current" and found this: http://www.allegromicro.com/datafile/0704-015.pdf

Hi nutty boy! I can tell you right away.. it's impossible, it can be everything from a few mA to several amps ::) No one can possibly tell you that if you don't tell us what kind of transformer you have it would just be a huge guess to estimate from one clue "12 volts" How big is the transformer 1x1m or 5x5cm, what kind of core toroid or laminated EI, wire gauge? Here is a software you can download and play with: http://student.math.hr/~sklaic/electronics/ This software might be a shortcut to estimate your transformers power handling capability ;D

That's possible but the H8V.93 seems to be part of the snubber so probably not a zener, I'll have to check the circuit again but not tonight it's friday and it's way to hot and I'm thirsty too ;D

Hi Stig and welcome to this forum! No haven't found any sub yet the project has been on ice for a while ;D there is also one more blown component and that is the thermal fuse which is open. Good that someone reminded me :) I'll start up again and if I find any sub for this diode I'll let you know.

Well that is a hard to tackle circuit I would say, to detect rf is one thing but discriminate between two cell phones make things a lot more difficult. As I understand (and what audioguru said) every cell phone has its own ID and when the base is calling one of the cell phones it answer, here I am go ahead! It means that to detect that a incoming call is directed to one of your cell phones you got to have a receiver with same ID otherwise the receiver/detector doesn't know which of them the base is calling.

Sorry I haven't read the other thread arsal_uet wrote. Audiguru if that's the case a detector is a simple solution but keep in mind that it will also detect every time the cell phone talk with the base don't you think? ;D MODERATOR EDIT: I have now merged the topics into one 5-3-2006

MP I agree, it's a good way to learn how component values change with frequency and bandwidth :) I'm sorry arsal_uet but audioguru is right about the filter, strong nearby signals from other cellular phones or base stations would probably be detected by your circuit. if the frequency would be fixed a narrowband filter could have been a possible solution but then we run into another problem and that is to design and create the filter which need instrumentation that is far beyond what most hobbie electronics can afford. I do encourage you to continue the project even though it seems to be a real hard thing to solve, don't give up there might be someone lurking around with exactley the right soulution for you, don't forget that you always learn something ;)

Rl= load resistance. To build a band pass filter 800-900Mhz is not an easy task I would say that some RF experience is needed. MP it's a good calculator but as you probably know both C and L involved in a band pass filter like this aren't what the average hobbyist usually deal with, I'm not an Rf expert but to get a proper band pass filter for that frequency sure some experience

Hi logan_dslasher! Yes it's for free you just have to click for free download wait 45 seconds, fill in three letters as shown and click download. ;)

That is one of the best notes written about scopes and probes, cynicmonster do yourself a favour and read them ;) Some of its content might not be written for a newbie but there is some useful reading for oscilloscope owners and for those who plan to buy one.

Don't know if you have any particular circuit in mind but here is a link where you should start your reading to get "some" understanding in resonant circuits, there might show up better places if you search google. http://www.ibiblio.org/obp/electricCircuits/AC/AC_6.html Oscillators is a huge subject, think you should do some studying by your own before you go further.

No you wont damage you scope just because the probes has more or less bandwidth than your scope. There is cheap good probes on the market for $50-$70, buy probes that have switchable attenuator, 1X 10X. Check this link, it's quite a common probe dc-150Mhz http://www.farnell.com/datasheets/32925.pdf

Thank's Ante! The 2SC5302 doesn't have any damper diode built in between collector and emitter. If you have unsoldered all legs there should be an infinite resistance between collector and emitter if not then your transistor is smoked, be sure that no legs are in contact with the the pcb traces.

RF Coil is just what it sounds like it's simply a coil and at RF usually one part of the oscillator that determine its frequency.

Hi prateeksikka! Just in case you want to play with another software, MMANA 2.03 is a very nice and accurate antenna analyzing software that will show radiation pattern in 3D, I've used it for a long time and it's for free ;) http://mmhamsoft.ham-radio.ch/

Is DE9704 the marking on your transistor? I'm sorry but never heard of it please check again ;)

C5302=2SC5302 these are japs :) No you can not just swap to another transistor unless you know it is an true replacement. Check the transistor you got in your spare monitor and let me knowwhat type it is.

Sounds like you figured out that the HOT was the culprit, about you question, it depends on where you live, what kind of transistor is it?

You are right Ante most probably the RF part need more than 9volts but somehow they will initially need more than 12 volts for the relay to activate, some battery powered circuits I've seen had some kind of momentarily higher voltage supplied to the relay to activate it and than dropping the voltage just to keep it activated thus decreasing the current through the coil and increase battery life as well. Adam can you see if there is any tracks that goes to components other than the relay, I'm suspicious about using a 24V coil in a device connected to a 12volt battery. Ante don't you think that18volts could be to much for the circuit to handle unless there is an regulator somewhere?

You are right it has nothing to do with a magnetized crt, I can't really come up with any bright idea. It sounds though that your problem could be temperature related, have you tried to switch to another resolution? If the focus adjustment potentiometer goes bad it usually show up either partly or all over the entire screen not any smudged colours like you have on the other hand a bad screen grid potentiometer could mess things up. Sorry but can't come up with anything else :(

Hi AdamUp! It depends on what the rest of this device want ;D a relay can be forced to activate by for a short time supply a voltage close to 24 volts, this voltage can probably drop down to 12 volts and still keep the relay activated so it might work with a 9 volt battery, try it. Well that just my 2 swedish kronor ;D