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Re: LCD TV Power Supply Woes

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  • Arthur Nichols
    As a PhD I was excited when I found this forum something like this would have been helpful when we switched from cats whiskers to valves, yes I was around
    Message 1 of 63 , Sep 1, 2011
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      As a PhD I was excited when I found this forum something like this would
      have been helpful when we switched from cats whiskers to valves, yes I was
      around then.

      I would like to build an ESR with a range selector switch, but for the
      reasons that I joined this forum I am not able to follow all the discussions
      and arguments associated with the build and use of an ESR which on the face
      of it is a fairly simple circuit.
      I am suffering from information overload. It is pleasing that so many will
      take time to constructively discus the finer points of electronics but I do
      have problems understanding some of what is said.

      My 64$ question, is there a site similar to
      http://ludens.cl/Electronic/esr/esr.html that will give me Full details of
      what to build.

      Or could someone summarise the Ludens circuit and suggest how it can be
      adapted to cover the points already discussed here and including a range
      selector switch.

      I have recently brought back to life a PC motherboard based on the fact that
      the electrolytic caps had expanded, I changed them and have a motherboard
      that is not yet going to landfill. I wonder how many items I could have
      saved if I had had an ESR.

      I like the forum but do find I spend time reading it when I should be
      decorating etc etc.

      Arthur
    • ae5ew
      5mv/div for vertical input would be considered good. You must have good grounds in order to get meaningful measurements at 5mv/div. That is with a 1x probe.
      Message 63 of 63 , Sep 1, 2011
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        5mv/div for vertical input would be considered good. You must have good grounds in order to get meaningful measurements at 5mv/div. That is with a 1x probe. 10x probe would be 50mv/div.
        Charles AE5EW

        --- In Electronics_101@yahoogroups.com, jong kung <jongkung01@...> wrote:
        >
        >
        >
        >
        >
        > > No because of the sensitivity of the measuring instrument.
        >
        > > The OP said he had a Heathkit oscilloscope. Say the
        >
        > > oscilloscope had a sensitivity of 5 mV/cm.
        >
        >
        >
        > Did he say that (I missed it then) - or is that a ball park for old scopes.
        >
        >
        >
        > =====
        >
        >
        >
        > > Next I estimate the signal source amplitude at the output
        >
        > > of the micro controllers is 3 volts peak to peak. For a 10 ohm ESR.the
        >
        > > output signal is approximately 20.6 mV peak to peak For a 1 ohm ESR
        >
        > > the output signal is approximately 3 mv peak to peak. For a 0.33 ohm
        >
        > > ESR the output signal is approximately 1 mV peak to peak. Hence the
        >
        > > output signal will be less than 1 mV peak to peak for a ESR less than
        >
        > > 0.33 ohms. I doubt if a meaningful measurement can be made with a
        >
        > > signal amplitude less than 1 mV peak to peak.
        >
        >
        >
        > Oh man... I have to go back and crack open my old text book on Freq & capacitors.
        >
        >
        >
        > Now I'm absolutely no expert on ESR, so if this is really dumb.... 
        >
        >
        >
        > Isn't 3 ohms about good enough for ESR meter ?  Aren't we looking for
        > higher ESR (because most likely the failed capacitors are
        > electrolytics).  Translated in other words, below certain low ESR, the
        > trace on the o-scope will be basically flat (good).
        >
        >
        >
        > =====
        >
        >
        >
        > > It is a good thing you asked why. Upon review I see I was to
        >
        > > pessimistic the first time around.
        >
        >
        >
        > OK,  I don't fully understand but I'll take some sugar when I can get it.
        >
        >
        >
        > :-)
        >
        >
        >
        > =====
        >
        >
        >
        > > To measure ESR less than 0.33 ohms one could reduce
        >
        > > the size of the 1K resistor to say 100 ohms.
        >
        >
        >
        > (a) is 0.33 ohm realistic value ?
        >
        > (b) swapping 1K down to 100 ohm would probably not work because...
        >
        >
        >
        > ... because that makes the voltage greater than diode forward V and the
        > capacitor won't be isolated from the rest of the circuit (translation:
        > the capacitors then has to be removed from the circuit).
        >
        >
        >
        > I think the better option is to change the working freq (the real benefit of using a microcontroller over hardware IC).
        >
        >
        >
        >
        >
        > Jong
        >
        >
        >
        > [Non-text portions of this message have been removed]
        >
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