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From: mike on 28 Dec 2009 21:22
William Sommerwerck wrote:
>> You don't need a peak-hold meter.
>> You need a DC current probe and a dual-channel storage oscilloscope.
>> Conjecture is no substitute for measurement.
>
> Agreed, absolutely. But I don't have a dual-channel storage scope. I'd love
> to have one of those fency new ones with the LCD (???) displays, but I can't
> justify the cost, because I don't use it enough. My 25-year-old Philips is
> gathering dust, as it is.
>
>
Ok, then use a resistor as a current measurement and your scope in a
dark room.
You're gonna find it difficult to diagnose a problem if you can't be
bothered
to even attempt a look at the symptoms.
From: mike on 29 Dec 2009 09:03
William Sommerwerck wrote:
>>>> You don't need a peak-hold meter.
>>>> You need a DC current probe and a dual-channel storage oscilloscope.
>>>> Conjecture is no substitute for measurement.
>
>>> Agreed, absolutely. But I don't have a dual-channel storage scope.
>>> I'd love to have one of those fency new ones with the LCD (???) displays,
>>> but I can't justify the cost, because I don't use it enough. My
> 25-year-old
>>> Philips is gathering dust, as it is.
>
>> Ok, then use a resistor as a current measurement and your scope
>> in adark room.
>> You're gonna find it difficult to diagnose a problem if you can't be
>> bothered to even attempt a look at the symptoms.
>
> That's a pretty rude thing to say.
>
> The original posting was a question about why most samples of a particular
> switching supply would not turn on when powering a device whose drain was
> well below the supply's stated capacity. There was no "problem", as such --
> merely an issue of curiosity.
>
> The conclusion was that there was sufficient current inrush to force the
> switching supply to briefly cut off. I've since found that if I simply leave
> the supply on, it will eventually "come 'round", though it might take 10 or
> 15 seconds.
>
>
>
Conclusions with no measurement are called conjecture.
My pet peeve with newsgroups is the massive amount of baseless
input that's presented as FACT.

Problem is that people asking the question probably can't sort
the good info from bad advice. If they could, they wouldn't have
needed to ask the question.

In a perfect world, all electronic designs would be "robust"
and every bit of advice would be good advice.
Sadly, it ain't so.

When you substitute part of a system without knowing
the issues and experience symptoms you didn't expect,
it's time to worry whether it's a good idea.

Conventional wisdom suggests you should beef up the current limit
so it doesn't cycle.
Be prepared for the possibility that the "correct supply" has
soft-limit features
that control the startup current and that substituting with one that
doesn't have a soft limit may prove very stressful to the system.
You might want to implement a softer limit rather than a harder one.

You have a scope...plug it in and find out what's happening.
A two-minute experiment is way better than all the baseless conjecture
you're gonna get here.
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