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January 2011

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Subject:
From:
stephen gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, stephen gregory <[log in to unmask]>
Date:
Fri, 14 Jan 2011 07:36:37 -0800
Content-Type:
text/plain
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text/plain (145 lines)
Inge, send me a picture and I'll post it...
 
Steve

--- On Fri, 1/14/11, Inge <[log in to unmask]> wrote:


From: Inge <[log in to unmask]>
Subject: Re: [TN] a different Friday quiz
To: [log in to unmask]
Date: Friday, January 14, 2011, 8:45 AM


It looks like Steve got no time to fix the photos for you this day.

Inge



----- Original Message ----- From: "Inge" <[log in to unmask]>
To: "TechNet E-Mail Forum" <[log in to unmask]>
Sent: Friday, January 14, 2011 3:40 PM
Subject: Re: a different Friday quiz


> 
> 
> Yes, I know that, have been analyzing a lot during the years, but this seems
> a little different. Note: 1. the   unit has never been exposed to any other
> environment than inhouse atmosphere.
> 2. The screw is not in contact with anything else than copperless FR-4.
> 3. Only one screw has this corrosion.
> 
> Inge
> 
> 
> 
> On 14 January 2011 12:07, Mike Fenner <[log in to unmask]> wrote:
> 
>  Some corrosion, once started, can self perpetuate by feeding on atmosphere
>  water and CO2, with no need for differential metals etc.
> 
>  Regards
> 
> 
>  Mike
> 
> 
>  -----Original Message-----
>  From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric Christison
>  Sent: Friday, January 14, 2011 10:48 AM
>  To: [log in to unmask]
>  Subject: Re: [TN] a different Friday quiz
> 
>  I'd go for galvanic corrosion in a mildly corrosive atmosphere, or
>  possibly highly corrosive depending upon your taste in food.
> 
>  You didn't ever drop it in a bowl of Kimchi did you, or that Icelandic
>  dish of basking shark marinated in caustic soda?
> 
>  Imagine periods of high humidity and temperature changes where moist
>  contaminated (salty?) air is drawn into the enclosure where it condenses
>  on the screw head. I bet you have dissimilar metals connected together
>  which will cause corrosion and the condensing air will drip off the
>  screw head to move the corrosion products around the inside of the device.
> 
>  Regards,
> 
> 
> 
> 
> 
> ----- Original Message ----- From: "Inge" <[log in to unmask]>
> To: "TechNet E-Mail Forum" <[log in to unmask]>
> Sent: Friday, January 14, 2011 12:06 AM
> Subject: a different Friday quiz
> 
> 
>> 
>> I bought a digital temperature equipment, consisting of a inhouse table
>> unit and a outdoors unit. Cost = 25 USD. Cheap? Yes. But let's have a look
>> on inside after the problem, which started just a few weeks. You can read
>> the inside temperature, clock works, date works, and you can use the alarm
>> and shift between the four channels, but the receiver does not take in the
>> signals from the little sender on the  wall any more. I dismantled the box
>> and marvelled when I saw the shit I payed for. It's a wonder that there
>> are any functions working at all! Now, what caused the dead receiver was a
>> flow of iron from one screw (upper left  corner ) . There is a bridge of
>> corrosion products  (brown and green) from the screw to the thermistor
>> (RT) continuing to the rest of the circuitry.  When I washed the card and
>> dried it, the reciever worked again,
>> 
>> Now, folks, here comes a question for the sharp TNetters:
>> 
>> "How can the screw be so rusty and deliver iron ions when it's not
>> connected to anything? It's just torqued into the plastic body. The other
>> screws are identical, but  have not been involved in anything. "
>> 
>> The box has been on the kitchen table and has not been exposed to humidity
>> or any else abnormal condition.
>> 
>> The two 1.5 V batteries are removed on the pics.
>> 
>> Hope the gregorian Steve will help me with the photos.
>> 
>> /Inge
>> 
>> 
>> 
>> 
>> 
>> 
>> 
> 


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