Hi Fabio, I remembered some problems soldering manganin a while ago, so I googled and this one came up:http://listserv.ipc.org/scripts/wa.exe?A2=technet;a5280f30.1203 So it is possible not all the previous flux was removed. I thought it was fairly stable, hence a good bet for standard resistors, but if overheated like you suspect then all bets would be off as they say. MK
> Date: Tue, 19 Jun 2012 20:04:40 +0200 > From: [email protected] > To: [email protected] > Subject: Re: [volt-nuts] Wanted wirewound precision resistors and ESI DB877 > > Here I put some photos of the decade: > http://www.eevblog.com/forum/product-reviews-photos-and-discussion/db877-teardown/ > > Frank Stellmach <[email protected]> ha scritto: > > I think, you should better measure the resistance by a high > > resolution DMM, on its normal OHM range. > > Thats much more stable and less power is dissipated. A comparison > > between two of them is also much easier. > > Yes I'm using a pair of multimeters: the keithley 2015 and > a solartron 7061, the keithley should be not far from real > values, but has a maximum count of 1200000, the > solartron is "zeroed" against the keithley, > has a maximum count of 21000000, permitting to compare > the 1M and 2M resistors without changing range and resolution. > > I used the fluke to try to test for leackage, I > tought that if there was some leackage, the current > would have been higher than V/R ratio and not > proportional to the voltage. > > > ingresses between the windings. I assume, your resistors are tubular > > ones, with plastiv caps around, and they are not hermetically tight, > > therefore they cant be filled completely for corrosion protection > > and thermal conductivity, like in the Vishay metal foil VHP type. > > See the link, there is a pic of the resistor, it's open, no protection > at all. > > > > > Besides electrical measurement (on OHM range!), I 'd recommen > > optical inspection of the case, and if its possible, of the windings > > for burnt/overheated areas. Corrosion may be easily identified, also > > by slightly stained parts of the wire. > > yes, the low valued resistors (10/20 ohm) seem a little corroded. > The intermediate valued ones seem ok. > > Is the wire used (manganin?) prone to corrosion? > > Fabio. > > ---------------------------------------------------------------- > This message was sent using IMP, the Internet Messaging Program. > > > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
