Ultimate shame: I bought it on eBay, a cautionary tale

[Phil_S]

There it is right up front. I think the tale is worth sharing for those who dabble in eBay for assorted stuff and there is some minor entertainment value in it, too.

Some time ago, likely more than a year, I bought 100 pieces 1R 1% 0.5W resistors for cathode senors. I wouldn't have paid very much because I know how easy it is to get burned. I can't find the transaction, but I'm thinking it was less than $4 shipped, so this isn't about the money. Heck, I'm quite certain everyone here has paid more for less of an education.

I finally broke the bag open to use a few. I could already see through the plastic the leads were too flimsy and that's got to be why I avoided using them. I thought, well, I can live with flimsy if I'm using tip jacks -- no real abuse on those leads with meter probes or clips.

An important aside, somehow my needle nose pliers got magnetized and I'm very unhappy about that...

I put my needle nose in the bag to grab a few and, whoa the resistor leads are sticking...WTF...magnetic leads. This can only mean one thing, that the leads have ferrous metal content

I suppose there is no salvaging these as the resistance of the leads will increase as they heat up. Is that right? I'm checking...these need to go right in the trash, don't they?

Then I need to find some others. BTW, cheap as they are, they mostly meter OK at 1R. I had to rig a 10R in series to get a decent reading, but they seem to meter fine.

[stretch2011]

Ugh. I bought some Chinese carbon films for super cheap off eBay. I hope I don't have the same problem

[Blackburn]

I wouldn't feel too bad Phil. We've all felt the allure of the ultra cheap components coming out of Asia. I certainly wouldn't call it "Ultimate Shame". Reserve that title for the dumb bastard that pays the asking for this...

http://www.ebay.com/itm/ELENCO-RS-500-1 ... 0969160155



Here's the same one that I just ordered...

http://www.testequipmentdepot.com/elenc ... /rs500.htm

[martin manning]

Lots of component leads are magnetic now. I don't see how this is a problem.

[David Root]

I must have bought the same brand but 100R 1W with thin magnetic leads. From a local store where everything is from China including the owner. I've been using them as faux CT on heater supplies, where the iron leads doesn't matter.

For 1R cathode sensors I pony up and use Mills 5W 1% wirewounds. Very accurate and they will never act as a fuse in the middle of a set--yes that has happened to some, that's why I don't use 1/2W there. I have though used cheaper 2W on low power amps 15W or so.

Martin you're probably right about magnetic leads in MI amps, but you should hear the audionuts on that topic, they are 110% agin it. Makes one wonder about inductance of wirewounds as power tube cathode bias resistors!

[Phil_S]

Lots of component leads are magnetic now. I don't see how this is a problem.

Maybe not for the little bit in those resistors...I forget what the stuff is called, but they use wire with ferrous content for some kinds of heating equipment, where they rely on the resistance increasing when heated basically as an off switch, to interrupt the flow of electricity once the device ignites the fuel. I'm not talking about a thermocouple, probably a special case of this, but about stranded wire. I admit to being fuzzy on this. I bought some once not knowing what it was and wired some filaments with it. Voltage kept dropping...

[Leo_Gnardo]

OH for petes sakes, get a little iron in your diet. The last thing I'd worry about is leads on a one ohm resistor being magnetic. Those hi fi nuts are for the most part WACKO especially about something like this. You build on steel chassis? Heard lots of amps that sound great built on them? How about those transformer cores? Iron = pure audio poison, right? Crikeys !

I'd be more worried about those one ohmers turning into little fuses. I know it's "theoretically" impossible. There was a long thread about this on MEF about 2 years ago. One of the techs bought something that sounds like the ones you have, poxy little things that looked like 1/8W but were rated for half a watt. They kept going open circus. So much for theory, those dinky "new wave" resistors can't handle the strain.

Get yourself some proper 1 ohm 3 watt 1%, pay the rate, suffer no more. Mouser is your friend. That's what I use, don't cut corners. They even have a good survival rate in case your tube goes short circus. And don't sweat over magnetic leads. Just keep 'em away from your compass when you go orienteering.

[JazzGuitarGimp]

I'm with Martin. I have noticed magnetic attraction to component lead clippings for years, probably even decades. I don't think it's an issue.

[Leo_Gnardo]

I'm with Martin. I have noticed magnetic attraction to component lead clippings for years, probably even decades. I don't think it's an issue.

My feet aren't magnetic but lead clippings like to stick there too when I go barefoot in hot weather. Some people have reported finding them (lead clippings not my feet wise guys) in their cat litter box, having passed thru the cat. Little snookums doesn't care, magnetic or not, they're tasty.

Phil, and evvabody else, if you have a tape head demagnetizer or bulk eraser, that'll clear the magnetic field from your tools. Those Annis demags that weigh about a kilogram apiece, perfect for the application. When the cut leads don't stick to your cutters/pliers anymore you'll stop worrying about the whole subject, one less thing to worry about.

[cbass]

Pretty sure 6ps and PVC caps have ferrous leads. Ive checked various old carbon film resistors they're magnetic but not as much as the new ones

[Leo_Gnardo]

If you must have something to worry about, keep magnetic materials out of the insides of MRI machines. One of my customers offered me some special RG-174 mini shielded cable that was all copper conductor, made for such use. Drat he never came thru with it. Put a magnet on your '174, you'll find 3 or 4 strands of steel running down the middle, mixed with copper strands. That would make it just about useless for those corque snivling high figh types, wouldn't it. I used it on ion implanters, never a problem. All the ions got where they were s'posed to go, none got cornfused by spurious magnetic fields.

[Structo]

I don't really understand where the issue is about magnetic leads.
Can they affect the circuit?

Most have some kind of plated steel in them.

I always thought if you really want to get nit picky, to use
non inductive resistors if you are concerned about something.
I think they use brass end caps.


That's how the Hi Fi dudes roll.

[John_P_WI]

Phil,

Over the Christmas holidays, I had 3 different Chinese ebay transactions:

1) For unobtainium SS power amp driver chips
2) For unobtainium Bucket Brigade Delay chips
3) For nearly unobtainable 1N34a germanium diodes

Um yeah, I received them fast... that's all I say.... Pissed a good combined 30 dollars away - they see us coming a mile away and know that the transaction won't be contested for 5 or 10 dollars, which propagates the counterfeit / fraud transactions even more.

[Zippy]

I don't really understand where the issue is about magnetic leads.
Can they affect the circuit?

If you're afraid of magnetic fields, don't pass current through 'em!

Most have some kind of plated steel in them.

There are likely a lot more parts in the ol' bin that are steel (vs copper), just waiting to become magnetized. I've probably never noticed because I use surgical grade stainless steel hemostats at my bench.

[Structo]

So stainless steel is non ferrous?

I think some SS has more iron in it than other.

I had a refrigerator that was stainless and the magnets wouldn't stick.

It was great to see a fridge that wasn't covered with photos and grand kid art.