22 uF/35 vdc tantalum capacitors CHEAP!

[k4kyv]

Not!

Order Here

[DMOD]

That's about what NTE charges as well.

Mouser and Allied have them cheaper.

Phil

[k4kyv]

Mouser charges about half that.  I was looking somewhere on-line recently for another product, and ran across them for about 35 cents each.

[Pete, WA2CWA]

If someone doesn't like the price for a particular item, they don't buy it if they have other choices. The vendor obviously feels they have a market to sell at that price or they wouldn't be selling it at that price.  I don't see the point of vendor bashing, shame-shame vendor pointing, etc. If you're willing to shop, and have the time, you can look for the price that best suits your life-style and financial position.

[k4kyv]

Electrolytics are considerably cheaper, and some say more reliable than tantalums.  Apparently the primary advantage of tantalums is small size when miniaturisation is a premium, but there are other reasons to use them, too. Here is an interesting (long) discussion of the topic

http://www.electro-tech-online.com/general-electronics-chat/26407-electrolytic-caps-vs-tantalum-caps.html

Tantalums are not unreliable if properly used. However: their ESR (series resistance) is so low that they have large inrush surge currents if the current is not limited by some means. That can cause them to fail. We used solid tantalums in many military products because their ESR remains low over the full temp range while aluminum electrolytics have ESR go straight up at temps below about 10C. You have to know what you're doing to design with solid Tantalums, but they are good for specific applications.

[The Slab Bacon]

I absolutely despise tantalum electrolytics! ! ! ! !  Especially the earlier and first gen ones. They almost always seem to fail to a dead short, taking lots of other stuff out with them. They had serious reliability issues.

I'm told that the newer ones are much better and much more reliable. But as an old saying comes to mind: "Once bitten, twice shy". I will replace them with aluminum electrolytics wherever possible.

[K5UJ]

  I don't see the point of vendor bashing, shame-shame vendor pointing, etc.

Uhm, it's called consumer advocacy and free speech.  You know, ePinions.com, Yelp.com, eBay vendor ratings, Consumer Reports magazine....things like that?  Do you have a problem with over-priced parts being called out?   It's one thing for an individual overpricing some used part he got at a fest and flipping it on eBay.   I think that stinks but a commercial vendor should be held to an even higher standard, don't you agree?   

This isn't a free market good/bad issue; it's a, aren't I allowed to say what I think? issue.  does it have to have a point?  Maybe it doesn't have a point.   So what?   

[W4NEQ]

I think the Tantalums' advantages are smaller size and lower esr.  But as previously mentioned, and in my experience, after they get some age, they do seem more failure prone.  Of course electrolytics dry out too ...

Chris

[ EDIT:  Tube stuff doesn't use electrolytics ...  Don, have you adopted solid state ? ]

[WQ9E]

Add me to the tantalum hating group.  That is the only high failure item I have run into in my Tektronix 7000 series scopes and plug-ins.  When I acquired my Drake MSR-2 receiver it had a shorted tantalum preventing the BFO from working and fortunately the previous owner didn't leave it on in that position or other damage probably would have occurred. 

[k4kyv]

[ EDIT:  Tube stuff doesn't use electrolytics ...  Don, have you adopted solid state ? ]

Actually yes, a long time ago.  Let's see... the UREI BL-40 modulimiter, the DDS VFO I picked up at Dayton about 10 years ago, the SE-3 sync detector, my R-1000 general coverage receiver, my homebrew electronic keyer (that works but collects dust while I use the bug for CW), my homebrew CW cathode keying circuit built with a TV sweep transistor that keys low-level stages in all the transmitters - including the Gates BC rig @ approximately 200 MA, the control/indicator unit for the remote-controlled antenna tuners, all the power supply and bias rectifiers in the Gates transmitter, the back-voltage diodes across the DC relay coils in the T/R system, bias rectifier in the 805 modulator, rectifiers in the DC supply that operates the T/R control relays, rectifier in the Micro-Match reflected power meter, and I'm sure I missed one or two others.

If we ever have the dreaded EMP burst, I'll be an a world of hurt!  

Tube stuff does indeed use electrolytics.  Remember those old wet electrolyte ones that would spill corrosive gunk all over the chassis of early 1930s broadcast radios? We can likely thank Hitler, Hirohito and events leading up to WWII for accelerating the late 1930s development of "dry" electrolytics that don't have liquid sloshing around inside.

I have never consciously purchased tantalums for anything, but I'm sure some of my commercially-built stuff has them, including the computer.  I have a big box where I save salvaged circuit board scrap from everything from hamfest finds to crapped out consumer electronics junk I have discarded; that's where I obtain a lot of the miniature components used in solid state circuitry, so I may have inadvertently used a tantalum or two in my homebrew projects.  My tube stuff is all point-to-point hand wired; circuit boards and vacuum tubes operate side by side about as well as gasoline and cigarettes.

Regarding the $5 replacement capacitor, if a product has a known deficiency/reliability issue, admittedly due to the factory using a capacitor rated at too low a working voltage, shouldn't the manufacturer be willing to supply the part upgrade free of charge? Automobile manufacturers offer free upgrade kits or field service by the dealer all the time, when a weakness in the original design shows up or there is a recall.

[W7TFO]

The ephemeral mature of electrolytics drives me to replace/build with either PIO types or fast polypropylenes.

They are non-polarized too, so I can't hook 'em up backwards.

73DG

[kb3ouk]

Did you ever think the reason the price for that capacitor is so high is because it is a replacement part from RF Concepts for one of their amps? Look at how overpriced the rest of their stuff is. They probably bought the thing from the manufacturer for a couple cents, then sell them $5 a piece to make a good profit. It wouldn't surprise me any if you asked them and they claimed that part was a "certified" factory replacement part, and that others' caps will not work as well, or some other crap like that.

[W1RKW]

tantalums seem to be less tolerant of voltage excursions beyond ratings compared to electrolytics. It doesn't take much over voltage to blow one.

[Bill, KD0HG]

You will almost always find equipment manufacturers charging outrageous prices for replacement parts. That's a fact of life, Don.

Well, if you think about it, it probably does cost them five bucks to process, pack and ship that little $25 cent cap.

Many of the parts I purchase in the line of work are never ordered from the equipment manufacturer. Fans, capacitors, relays, solid state devices, I always buy elsewhere. The main exception is obsolete transistors and chips.

Bill

[W3GMS]

Here is a good description on modern Tantalum capacitors.  They do have some worthwhile attributes but the circuit designer has to know when and when not to use them and how to implement them properly.  I use to use them in timing circuits with great reliability and precision.  The "wet slug tantalum's" used sulfuric acid and have been gone for a long time now.  They tended to be problematic.   Kemet produced some fine tantalum's caps that were widely used in both commercial and military applications.  A good design engineer would know when and when not to use them based on the application. 

Below is from engineers.com

"A tantalum capacitor is comprised of a permeable tantalum center section surrounded by tantalum pentoxide. A tantalum wire is inserted into the center section and then extends axially from the component. The tantalum pentoxide layer is coated with manganese dioxide, graphite, a silver conductive coating and (finally) solder. Since 1960, tantalum capacitors have improved due to advances and development of higher charge tantalum powders, directly contributing to the design of smaller tantalum capacitors.

There are numerous advantages to using tantalum capacitors over other types of capacitors. First, tantalum capacitors have a higher volumetric efficiency (CV/cc) when compared to other types of capacitors. For instance, a 10-microfarad tantalum capacitor can replace a 100-microfarad aluminum capacitor. Tantalum capacitors are easily mounted onto circuit boards, and give engineering designers the ability to place these components in closely-confined printed circuit board space, as well as utilizing tantalum capacitors' excellent power dissipation characteristics. Second, tantalum capacitors have superior frequency characteristics than many other types of capacitors, including aluminum electrolytics. A comparable CV tantalum capacitor has an ESR ten times better than an aluminum electrolytic capacitor. Third, tantalum capacitors are highly reliable - electrical performance qualities do not degrade over time. Tantalum capacitors do not lose capacitance unlike electrolytic capacitors - in fact, the shelf life for tantalums is regarded as unlimited. Fourth, tantalum capacitors don't wear out - in fact, if there is an imperfection in the dielectric layer of a tantalum, the resistance of the manganese dioxide layer will typically convert to a form that is even more resistive. The new oxide form plugs up the faulty region and results in a reduction in current flow. Finally, tantalum capacitors have an excellent wide operating range, from -55 degrees Centigrade to +125 degrees Centigrade, with a minimal amount of degradation in electrical properties throughout this range.

As noted above, the advances and development of higher charge tantalum powders, have directly contributed to the design of smaller tantalum capacitors, resulting in the general downsizing of electronics. Tantalum capacitors can be found in laptop computers, airbag circuitry in cars and trucks, cell phones, pagers and a wide range of other electronic devices. The widespread use of tantalum capacitors in cell phones is one of the key factors in the significant reduction in the size of these devices during the past several years. Dell, Nokia, Hewlett-Packard, Motorola, IBM, Alcatel, Lucent, Compaq, Solectron and Ericsson are just a few of the companies that use tantalum capacitors in their wide range of electronic products."

Joe, W3GMS