Hi Fernando, Moose and all,
From: Moose <olymoose@xxxxxxxxx>
> 1. Failing battery. Although most characteristic of non-silver oxide
> batteries, I could see this happening with silver oxides at just the
> right stage in their useful lives.
Not to be discarded.
> The why is simple. Battery load in metering, lighting test button,
> operating self timer, etc. is quite low. AND, none of these but the
> battery check cares much about the voltage.
Certainly. Any battery (or power supply) may be conceives as a "perfect
voltage generator" (output voltage absolutely independant of load) with a
_resistor_ in series -- according to OhM's law, the voltage drop at the
resistor depends on the sourcing current (mA).
> BUT, battery drain holding the second curtain open during exposure is
> quite high.
In other words, a battery may give the correct voltage _without load_, but
fail to do so when a higher load is connected -- then the camera locks :-(
This is a typical behaviour of a failing battery, whatever the unloaded ("en
vacío") voltage reads.
> Unfortunately, the battery check light on the OM-4 series bodies is
> not very good. Check with a voltmeter.
Certainly. But please realize that typical digital voltmeters will read the
voltage "without" load -- in fact, a very tiny load, about 10 MOhms => 150
nA, yes, NANOamps. Some models have a specific setting to test 1.5 V
batteries, which apply some load to it.
Fernando wrote:
>Done. My new Renata 357 batteries measured 1.5 dead-on.
Seems a bit low, brand-new SR44s or 357s should be close to 1.58 (as Moose
checked) without load...
> If voltage is below 1.5v, try another set. It doesn't matter if the
> batteries are "new", as manufacturing defects or time in the
> distribution channel crop up from time to time.
Sure.
> 2. Poor electrical contacts in the battery circuit.
From the view of the camera's circuit, it's the same as a bad battery --
increases the parasitic series resistor.
Fernando again:
>Most probably this one may be the cause. Glad to have ruled out the
>memory clear button and the self-timer left On.
The reset button was unlikely, since the viewfinder display was OK.
>Removed the batteries, measured them, cleaned both at each one's
>surface, inspected the batteries chamber and everything looked quite clean.
But the contact point of the camera is just a tiny sping... check it out!
>Put the batteries again, tightened firmly and fired: it failed ... red
>1/60, fired again: it worked.
Well, in red 60 should work regardless of power... or do you mean it worked
after going to "electronic" speeds again?
> The why is similar to above. At low current, there is little enough
> resistance through the problem spot that everything seems normal. With
> higher current, the voltage loss across the poor connection is great
> enough to lower the voltage too much for shutter operation.
>
OhM rules !!
As already said.
> If truly fresh batteries and tightening the bottom plate screws don't
> cure the symptoms
And don't forget to clean (or even stretch a little) the tiny
spring-wire-contact in the battery chamber...
>BTW, this failure made me remember of very recent one I had.
>Strangely enough, I hadn't use my power amplifier since maybe the
>beginning of June (nor had I used the 4Ti, which arrived on those days -
>that is almost the whole winter).
>On August 24, I turned it On. No sound from the left loudspeaker,
<snip>
>The other two switch
>the amp from balanced to single-ended inputs,
I told you before what I think about that... Using bad quality switches for
a completely unnecessary feature ;^)
>Most probable, the balanced - single-ended selector
>switch got dirt or moisten (we have cold an humid winters here). At
>first, left channel didn't sound as loud as it should, repeated the
>procedure and it's now as good as ever.
Quite usual. My "macana" Pioneer got the 'A' set speakers sounding awful,
because of oxidization (sp?) on the relay contacts, I think.
>And all their screws are perfectly black ;-)
Black is good for other things, but not for this ;^)
>--- does the idiomatic expression 'loose screws' mean something for
>English speaking people?
LOL!!!
Cheers,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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