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Re: [OM] OM 4Ti mirror lock up - but batteries are Ok.

Subject: Re: [OM] OM 4Ti mirror lock up - but batteries are Ok.
From: John Hermanson <omtech1@xxxxxxxxxxx>
Date: Fri, 28 Aug 2009 08:48:19 -0400
Be careful regarding the spring in the battery box.  It is a press fit, 
any pulling may cause damage (or you might find the wire is no longer 
soldered to it).
___________________________________
John Hermanson  |   CPS, Inc.
21 South Ln., Huntington NY 11743
631-424-2121  |  www.zuiko.com
Olympus OM Service since 1977
Gallery: www.zuiko.com/album/index.html


Carlos J. Santisteban wrote:
> 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,
-- 
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