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 >> >> >> >> >> >> >> > ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------