Cheap Ceramic caps... Grrr

[Terry_VK5TM]

I bought a bulk lot of 0.1uf ceramic caps from eBay a while ago as I was running out and finally got round to opening the bag to use a couple yesterday.

The leads had gone RUSTY, so be careful buying even just passive components now.

These have thin leads about 1/2" long and turned out to be magnetic as well.

Needless to say, they are now taking up space in the bottom of the rubbish bin awaiting their opportunity to add to landfill.

[Maarten]

Iron is also used by reputable brands, but they will at least plate it sufficiently.

[joebog1]

Maarten beat me to it! Even Philips resistors had steel leads in the 70's. It's a resistor after all. But yes, it's bad. Unless you spend a fortune most component leads are steel these days, as are IC pins in many forms. I haven't used chips for at least 20 years but they were steel back then too. I'm talking 1980's.

Joe

[MrBungle]

I would never buy any parts off eBay these days. So much junk it’s unreal.

A good “middle of the road” option are the “suntan” branded NP0 and X7R ceramics being sold by Rapid Electronics. Pretty cheap and are excellent capacitors.

[Argus25]

There are a lot of very poor quality new manufacture parts out there. I was concerned about 0.1uF ceramic caps too.

I wanted axial ones and discovered a quality issue with new ones.

There is a solution to the problem though and still buy things on ebay. You simply go for new old stock from a known MFR. So in the case of the 0.1uF caps I went for ones made by the Corning Glass Works, photo attached, excellent quality.

I do the same buying transistors and always go for what looks like genuine old stock, known MFR, preferably mil spec type, the quality is better than new ones. Its only been in the last 15 or 20 years that electronic component quality has really gone to the dogs.

[evingar]

Originally Posted by MrBungle

I would never buy any parts off eBay these days. So much junk it’s unreal.

A good “middle of the road” option are the “suntan” branded NP0 and X7R ceramics being sold by Rapid Electronics. Pretty cheap and are excellent capacitors.

Ditto.
With ceramic caps there is an enormous variation with dielectric type. Some types roll off their value with applied voltage so you can get nowhere near the value you think you are getting. If the dielectric type isn't stated and the caps are just sold as "ceramic" expect the worst and avoid like the plague.

[MrBungle]

Indeed. To illustrate how bad they are:

1. Temperature-wise. If you merely pinch one for a few seconds it can lose shift 40% of its value just by the average 10 degree change.
2. DC voltage. 20% of the rated DC voltage across it can lose ~60% of the capacitance.

I've tested this myself with an LC meter and some cheap ones from Tayda.

Literally Y5V etc are only good for very low voltage (1.8-3.3V) decoupling and that only saves a few cents per board so for massive production runs. Problem is the Chinese get their hands on a reel of them and repackage them as dipped TH ones and sell them because neat organised capacitor packs are attractive products.

Applications:

1. Use C0G/NP0 for timing / critical applications. These have minimal temperature drift. However only use them to 5-10% of their voltage rating. 1pF -> 1nF
2. Use X7R for decoupling / coupling. These have slightly worse temperature drift but usually isn't critical. Mainly price/capacitance cheaper. 1nF - 1uF.

[Terry_VK5TM]

Originally Posted by MrBungle

I would never buy any parts off eBay these days. So much junk it’s unreal.....

I normally use Mouser or RS, but the freight in this case was going to be more than the cost of the components (and in the case of RS, dearer than could be justified at the time, even with the free freight).

As they were only going to be used for supply decoupling, tolerance etc was not too much of a concern.

Oh well, live and learn.

[arjoll]

Originally Posted by MrBungle

A good “middle of the road” option are the “suntan” branded NP0 and X7R ceramics being sold by Rapid Electronics. Pretty cheap and are excellent capacitors.

In this part of the world, that's the brand Jaycar do - might be useful for Terry as there's probably a store nearby.

I have generally been buying stuff from element14 instead though - I don't use enough of them or have sufficient knowledge to know if I've bought dodgy parts or just whipped up a dodgy circuit

[MrBungle]

Also importantly, unlike the Murata ones, you can read what's printed on them!

Your latter point is one that I spent years getting bitten by mainly due to schoolboy poverty. It contributed to the universal lack of success I had in my early experimentation with electronics. I had no idea if it was the test gear, the parts or my knowledge which was wonky. So after 40-something years of wiggling out of this, stuff is finally starting to work!

[TonyDuell]

I agree. My time is not worth much but even so I have better things to do that chase 'faults' caused by components that are not what they claim to be. I only use E-bay type places for 'new old stock' components that I can easily test when they arrive.

I normally go to RS, sometimes Farnell (both are equally reliable in my experience, it's just that the former is more convenient for me). Not only do you (almost always) get what is claimed, but if you do have a problem (and this has happened only once to me over many years) you can send them a (polite) comment and they will try to help.

[whiskas]

I must admit the quality of many Chinese made components are quite shocking - not to mention the massive amount of counterfeiting going on , particularly of semiconductors and even capacitors now...
I've had new electrolytics that measure way under the stated value, for example.

I would say use ebay, but be selective - try to find from UK based sellers that are selling genuine factory surplus etc, as this is usually sourced from higher quality components manufacturers.

[ionburn]

I find there are good things on Ebay, but prefer to buy from established suppliers if possible. One issue these days is to get things in sensible amounts. Do you buy 20 years worth and end up not using much or one or two and pay through the nose. There is scope for a system here although perhaps too complex to setup. I presume clubs do do that. With RS I have had (personally and company wise) issues over the years but they do sort quickly without quibbles. I think, like many things, you get what you pay for.

One thing I have noticed with Uk based sellers is that many of them are now local distribution points for Chinese components (some even with Chinese seller information).

[evingar]

Originally Posted by ionburn

One thing I have noticed with Uk based sellers is that many of them are now local distribution points for Chinese components (some even with Chinese seller information).

Indeed. The "UK" filter often still lets through results from these faux UK sellers
One thing I don't understand is anything from the US usually costs ££££ postage and invariably gets clobbered by handing charges and customs charges but stuff from China is frequently free postage and seems to circumvent the other 2 charges as well - how does that work ?

[MrBungle]

Most of the problems I've had with RS are involving ParcelForce to be honest. I ordered 25x 4.7M resistors once and received a £50 bag of varistors though. I told them and they said keep them! That was a good day as I got a curry out of the sale price

Best to avoid the Chinese sellers drop shipping. They care even less as most of them seem to be running several accounts from one warehouse so when they burn all the good will on one, another pops up.

If you report the seller for misrepresenting the item location they disappear pretty quickly.

[Mike. Watterson]

The sending country decides the postal charge.
Canada, France, Belgium and USA are bad.
Germany is as cheap to Ireland, or cheaper than UK.
China and a few other countries will use groupage, shipping containers and surface. So it takes 6 to 10 weeks compared to 1 week or less USA (air). Hence small packets cost nearly nothing.
In contrast anything up to about 20kg is about the same price for UK/European Courier to Ireland, but any Royal Mail, French, Belgian , Irish counter post more than a letter gets rapidly expensive so 2kg = 20kg Courier approx.
UK/Irish ferry based post abolished. All post by air now UK <->Ireland. I heard a rumour that N.I. post to Ireland now goes via International Sorting in UK Mainland.

[Bazz4CQJ]

Originally Posted by MrBungle

Your latter point is one that I spent years getting bitten by mainly due to schoolboy poverty. It contributed to the universal lack of success I had in my early experimentation with electronics. I had no idea if it was the test gear, the parts or my knowledge which was wonky. So after 40-something years of wiggling out of this, stuff is finally starting to work!

As a 10-year old, a shop in Leeds sold me a "ferrite rod" for a radio which I built which never worked. Years later, I found out that the rod was actually made of graphite .

B

[MrBungle]

That's quite funny. Similar problem in the mid 1980s here when I was young and gullible. The local radio repair shop guy gave me a couple of "OC71" transistors. I use quotes because I was told they were special metal ones. Turned out to be unmarked, untested silicon NPNs . I only discovered this when I found the thing in a junk box last year.

Thus proving that it's not just the Chinese or a modern problem

And how did I celebrate this failure? By immediately blowing my pocket money on some Bi-pak "special value" transistors...

[Craig Sawyers]

I still occasionally get suckered. Power transistors from a UK eBay seller (2SC3264/2SA1295 ). Before I soldered them in I decided to measure the physical dimensions and they were all slightly outside the specified.

Suspicious now I put them on the curve tracer. Original devices were sustained beta, and the fakes had lots of droop. And the Vceo for genuine devices is 260V, and the fakes are 120V. Original weigh 18g and the fakes 14g. I then depotted genuine and fake devices with a hammer, and found the original devices we 6mm square (so 36 square mm) and the fakes were 2mm square (so 4 square mm).

So buying from a UK seller is no guarantee alas.

Craig

[MrBungle]

One thing I have found that always works is gold base/leaded transistors. Those are too expensive to bother cloning I reckon! Scored myself a reasonable sized bag of MRF237's the other week. Very happy about that.