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Posts posted by SM2GXN

  1. Hi!

    Can anyone recommend a good book about stepper motors?
    It wont hurt if it is for free  ;)
    Yes I know that there is a great deal of info on the web about steppers but it's lot better to have it on my hard drive.

    Thanks in advance  :)

  2. Hi frankwas!

    This link will give you an idea about how it looks like in your car amplifier, guess you need at least 1000VA transformer for your amplifier if you want to rock real hard, 1400W that is lots of power, your amplifier might have more than two channels, can you take a snap shot of the inside?.
    Open the ampifier and run it from a 12 volt battery if you don't have a power supply that can handle the current needed. Measure from the the center tap of the transformer to the + and - side of the rectifier, the voltage reading you get is what you need  ;)
    The bridge rectifier usually consists of two 3-leg devices TO220 packages with two diodes in each, they are usually marked with diodes on their bodies and mounted to the heath sink.
    Someone will probably say that a bigger transformer is needed and that is both true and false, all depends on how loud you want to play  ;D


  3. Hi!

    No I'm afraid that I have to say no letter in return or any sign  :(
    The very last hing he said was that his computer crashed.
    We had a conversation on ICQ and at that time he was complaining about his health but a few days later he told me that he was getting better.
    I found Staigens phone number!!!!!!!!!!
    I just hooked up the phone and I have real good news, Staigen is as healthy as I am :) his computer has crashed as we already know but he haven't had any time to repair but he promised to show up as soon as possible  ;D ;D ;D

  4. Hi again Bob!

    His name is Stig and I did send the letter to his home adress I got his adress for long time ago because I was supposed to send him some junk :)
    As I said I've tried to search for his phone number but with no success, couldn't find a name that matched his in same area, maybe I should try to find someone in his vicinity just to ask if he is ok.
    Yes I know that he wasn't ok but last time I spoked to him he said that he was getting better, hopefully it's just because his computer crashed.

  5. :) Nice photo!
    SF465 K is a saw filter for the front-end of the receiver, there is two black two legged components, one is located to the right of the "tied to the antenna" hole and the second one just above SF465 K2, I guess these are pin diodes used as transmit/receive switch.
    My second guess is that the UDF is the power amplifier and the SMD transistor just below is the driver.
    Just guessing but think it's pretty close  ::)

  6. 65ShelbyClone I guess we need a schematic to be able to investigate if it is possible to increase the power, we don't know if they use transistors or a PA module.
    The only thing I know about these radios is that the frequency they cover can be changed on some models
    Would be interesting to see a schematic on one of these :)

    oldgrandpainmi I'll look out for you on the bands :)

  7. That's the whole truth oldgrandpainmi :)
    Use of an external antenna with higher gain is probably the easiest way to increase the range.
    If the antenna connector on these radios is BNC or TNC it's easy to make something that fit, to increase the transmitting power you need to dig into the radio and as oldgrandpainmi said you could do something that FCC don't like  ;D
    Number of batterys, driver and power amp transistor will set the maximum power you can get from your radios, to increase the power you probably have to replace the power amplifier transistor and modify the output circuit which match the antenna impedance so it is not that easy 65ShelbyClone they might even use a small pa module as power amplifier.
    oldgrandpainmi what is your call sign?

  8. Hi MP!

    You and oldgrandpainmi answered your question :) I apolgize I've missed it  :-[
    As you said higher voltage rating is equal to bigger size, let us take one example about size, a crowded pc motherboard usually got their filter caps real close spaced, replacing one of them with higher voltage rating is often not possible because of bigger can size. As most people that repair pc motherboards know dried out caps is quiet common today cause of bad choise of capacitors or bad designed VRM,s.
    Say you by a capacitor named something like Rulycon :) (sounds pretty close to Rubycon) some of these makers of caps has same can size as the original but some of these higher voltage rating, since these caps has higher ESR and badly mixed electrolytic formula they will pop sooner or later probably much sooner than a good cap, higher ripple current will kill the capacitor faster.
    It's wise to stay with good brand low ESR caps in SMPS I think you know that better than I do MP  ;)
    Another thought, if you replace a mains filter capcitor in a DVD player SMPS which is well screened in a metal box, say you find a capacitor with higher voltage rating but you find that the cap is taller which in turn will put top of the can very close to the screen box, these DVD players does "usually" not have any safety ground connected to its chassie, so what would happen if there is a short to the can? The DVD player might as well have more than 300 volts to its chassie.
    I just wanted to guard myself to another question if I had answered like this:
    It's just OK to put whatever you have in your junkbox as long as the capacitor has same capacitance and same or higher voltage rating.
    However, I didn't finish my job to explane why very well but I guess that there is lot more that can be said about this.
    English is not my mother tongue so hopefully you all understand what I tried to explane  :)

  9. Yes it looks like 10 ohms to me also.
    I've seen many different power supplies but never (I think) anything like MR8 and MR9 creating some kind of virtual ground.
    Have you measured for low resistance right after mD4 and mD6?
    I would measure both +32 and -32 to see if there is any difference in resistance.
    Check also +31 and -31 series regulator transistors mQ3 through mQ6, zener, caps and fets. measure resistance right after these series regulators as well.

  10. Hi pyroboy!

    The component that are marked as capacitors are probably ferrite beads and they are used as filters but there is two disc ceramic capacitors one each side of these beads, if there is a white ring around them it is diodes but I can't see any on the picture,
    The black thing is an inductor probably used as filter too, together with a capacitor it will make a lowpass filter, maybe for the dc voltage into the pcb.
    A small high voltage transformer like that is not easy to wind, you'll need a very very thin wire  ;)

  11. That really has nothing to do with his question. He wants to know the difference between inverters that convert 12VDC (I assume) to 120VAC or 240VAC.

    Sorry not my menaing to mix things up, I just wanted to explane the difference between horizontal and vertical frequency.
    No need to hang out my previous post just because it didn't stick exactley to his original question.

    My post was about this:

    i just wanted to know that can a hugh freq inverter drive normal transformer based power supplies correctly. generally all appliances are rated at 50/60Hz. SMPS based systems may not have a problem but what about normal TV sets which generally use the line volatge as the horizontal sweep freq. the transformer appliances may make a buzzing noise.

  12. Hi MNA!

    For couple of years ago I had dialup so I know what you are talking about :)
    There is lots of good books and web pages about transmitters, to understand those books you will have to read some fundamental electronics, there is really no shortcut you have to struggle through all of it :) but please don't give up even though some pages in a book seem to be the most boring you have ever read  ;)
    I'll do my best to find something and hopefully there is other people on this forum that can contribute too.

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