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Subject: Re: Maximum DC current in Archos FM?
From: TP Diffenbach (rockbox_at_diffenbach.org)
Date: 2003-06-29


Michael,

You're quite right. I shouldn't be doing this. I haven't the knowledge or
experience. Nor am I insulted; to the contrary, I appreciate your warning. There
are many many things I'm not competent to do. ;)

Here's my situation. Having replaced the hard drive in my srchos, I'm getting
pretty bad battery usage. It's not entirely clear to me what usage I'm getting, as
I've found that the battery power will drop far enough to turn the unit off, but
will re-bound when the unit's turned back on.

It also appears to drop when the unit's turned off -- to what the Rockbox software
calls 35% or so in the first hour after a full charging -- but not to drop furthre
than about 20%.

Naturally, the archos firmaware and the Rockbox software also disagree --
substantially -- about the current battery power.

Still, subjectively, I can tell I'm not getting the usage time I had been getting.

Ultimately, my aim is to repair if possible, any drain on my battery.

My proximate aims are the following:

I want a way of independently testing the batery, without the archos, to confirm
that it's not the battery that is damaged.

I want a way to make sure that there are no shorts -- principly, the archos
harddrive is covered with plastic, presumably to prevent shorts, as the negative
end of the battery is connected, via the battery access "door", to the back of the
archos case, which connection would also touch the harddrive were it not for the
plastic.

In opening the archos, I broke at least one solder point, which I suspect is
structural rather than electrical. I want to conform this suspicion, by testing if
any current flows through that solder point.

I'd appreciate your thoughts on how I might accomplish these objectives.

Thanks,
Tom

Quoting Michael O'Quinn <michael_at_oquinn.info>:

> Tom,
>
> Your question tells me that you maybe should not be doing this. I don't
> mean that as an insult, but you could very easily fry your Archos Box.
>
> First, do you realize that when measuring current (amperage) you must
> insert the meter INTO the circuit, not measure it ACROSS the circuit.
> That means that for each trace you would want to measure the current on,
> you would need to cut that trace and then use the meter to complete the
> circuit.
>
> If you attempt to measure current like you would voltage -- by placing the
> probes across the circuit you are trying to measure -- you will get either
> (or both) a blown meter (fuse, hopefully) or a blown Archos.
>
> Maybe you already know this -- and I apologize if that is so -- but in
> that case I would expect you to also know the answer to your question in
> the first place.
>
> To answer your question, I would imagine the charging circuits, voltage
> regulator, and the HD would need a heftier meter. Something that can
> measure 2 amps (2,000 mA) ought to do the job.
>
> Oh, there might be some AC in the voltage regulator and/or charging
> circuits, if they are switching rather than linear. And anything that has
> a changing signal is also AC. (Like the digital signals, and the analog
> audio signals, and the... Well, lots of things, actually.) Often
> electrical circuits have both an AC and a DC component.
>
> Just out of curiosity, what are you trying to accomplish with all of this?
>
> Michael
>
>
> On Sun, 29 Jun 2003, TP Diffenbach wrote:
>
> >
> > I'm trying to purchase a multimeter to trace the circuitry in my Archos FM.
> I
> > assume the current is DC. What's the maximum amperage in the Archos FM? Will
> a
> > multimeter that measures up to 200mA suffice (I suspect not)?
> >
> > Thanks,
> > Tom
> >
> >
>
>

-- 
Archos FM has a Rockbox!



Page was last modified "Jan 10 2012" The Rockbox Crew
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