Buying NOS Electrolytic and Tantalum Caps, etc, from Questionable Vendors...?

I hawk eBay a lot, looking for deals on unusual parts, and have bought parts in the past that turned out to not be what I was expecting. Cruddy caps with out-of-spec measurements, resistors sold as carbon comp that turned out to be film, etc.

We all know that there's significant market for counterfeit transistors, capacitors, and even diodes! You have to be careful out there!

And furthermore, some componants just don't age well... They might be authentic, but they've just been sitting for so long that they're no longer useable as intended.

So is there anything specific I need to worry about when buying new-old-stock electrolytic and tantalum capacitors? I realize that old electrolytics should be tested for rated capacitance and also for ESR (have an ESR meter on the way! Should be here next week), but what about tantalums? Do they "go bad" just sitting on a shelf? If so, what do I need to look for or test to be sure I'm getting good parts?

Any and all personal experience and technical info appreciated. Also, any info on other things to watch out for when shopping for used or NOS parts welcome, not just capacitors, but anything related, such as any tips on finding or testing for authentic germanium transistors and diodes, specific vendors to avoid, etc.

Thanks, and have a great day!

I buy tants on ebay and have had good luck.  I wouldn't even think about electrolytics.
Transistors not so much either.
Best,
Bruno2000

I am kinda wondering why you would want to buy nos electrolytics, they have a shelf life and there are plenty of excellent quality new electros to be had from reputable suppliers and brand names?

Yeah, buying NOS electrolytic caps seems a bit crazy. If you really do have an excellent reason to do so, perhaps you can re-form them by bringing them up very slowly on a DC supply.

Exactly my thoughts, but there's apparently a huge market for them, and any number of vendors are doing well selling them, so I thought maybe I was missing out on something. Some of the prices being asked are insane! Especially considering how many Rubycons, etc, are being faked, you can't even be sure you're getting the real deal!

I guess it's like anything else, when it comes to fools and their money..

Good to know about tantalums though. There's plenty of deals out there on those.

Anyone have any experience with these chinese copies of various old transistors? Before I knew what I was looking for I bought some 2n2222a in TO-18 for a price too good to be true, and while they seem to be in-spec for hfe, they are clearly newly manufactured parts. Are these likely just 2n3904 or 2n4401 or something with a stamped metal cap on them? I guess anything like this should be totally avoided, right?

I'm not sure I would buy any parts on Ebay anymore.  Certainly not anything sought after.

I bought some original 2520 back in the day, maybe 10 years ago before Fabio's clones etc.  It occurred to me very quickly just how easy it would be to  fake a 2520 and command $100 a pop…Same goes for transformers etc.

My advice- Don't buy anything from questionable vendors. 

What are your guy's thoughts on paper caps?
I have a bunch of jensen 6uf paper caps that came from a tube based reel to reel player/recorder that look to be in good condition as well as a ton of others I was saving them for a ptp project.
At what point should i discard them? Some were pulled from old tube amps while others are NOS, do you guys recycle caps?

Rocinante said:

What are your guy's thoughts on paper caps?

Click to expand...

Bin them.

Thanks folks!

Another question concerning NOS electrolytics... I finally have an ESR meter (Peak Atlas ESR70) and took the time to dig through my trays for Nichicons and Panasonics I bought more than a year ago, and they all tested good for capacitance and ESR.

I also visually compared them to parts from the same manufacturers and series (i.e. Nichicon VX or Pana FC) and I am convinced they are authentic.

The question is, is there anything else I need to test or worry about before using them in repairs or DIY builds?

(thanks abbey, for the move!)  8)

I'd be pretty careful about buying NOS electrolytics and I'm not really sure what the point would be.  It's not like they're going to have some magic sonic quality that you won't find in new parts. If anything, I think they would be more likely to cause sonic problems, compared to new parts.

But if you insist, it would be wise to check leakage current at rated voltage, especially in the case of higher voltage caps. For older electrolytics, this is probably more important than ESR tests . The old Sprague capacitor testers did this and some new cap checkers do as well. If you don't have a cap checker that performs this test, you can do it with an HV bench supply and a current meter. You need to be careful not to shock yourself, and not to exceed the current rating of the meter. If you can find a copy of the manual for a Sprague TO-5 or TO-6 capacitor tester, you'll find good explanations of these tests.

+1 not a fan of old electrolytic caps. If old enough they may need to be formed-in, so initial leakage measurements may be inaccurate. 

Modern caps will pretty much always be better in every metric.

JR

Hopefully this is on topic and not a threadjack....

I'm currently trying to decide whether to take a gamble on some Chinese transistors or wait 3.5 months for mouser to be back in stock.

I have a pair of LAZ 525 kits, and I need a pair of vcr2n. Mouser expects to have more stock in mid-October, but I don't want to wait that long. There's a couple of Chinese sellers on ebay, one even has them listed as Vishay/Siliconix for $5 each. Worst case scenario is I buy a pair, they turn out to be bunk, and I'm out $15 including the shipping, so not much risk involved, just the wait on mouser. However, I really don't want to support scammers, as that just encourages more scamming.

I've never bought components from China before, so I have no gauge on my likelihood of getting screwed over. Anyone have advice?

At this point I pretty much assume everything from Chinese ebay sellers is fake or mislabelled/misrepresented garbage. Just look at the enormous market for rebadged Schottky diodes being called "germanium"!!! I accidentally bought some of those from a guy in Europe, sight unseen, and of course they're tiny little DO-35 diodes which cannot possibly be point contact germaniums.

I've have had luck with several Taiwan vendors however, namely "electricslee" and "flute570606", and of course the various Tayda accounts on there have been hit or miss, but generally okay I guess. Tayda certain has great prices and ships pretty quick. Those first two vendors seem to have a nice stash of NOS parts, all seem to be genuine, but their prices are pretty high and shipping can take 2 weeks to get to the US.

My opinion, and I'm sorry if this seems harsh, but if it's from a Chinese vendor then buy at your own risk.