[dewitt]

Super informative post. Thanks for sharing.

One thing I didn't understand was the author's comment that "I bought the part off eBay, not from a reputable supplier, so it could have come from anywhere."

A 5-pack of quality 7805's can be found on Amazon for $5, including Prime shipping, (e.g. http://amzn.com/B00H7KTRO6), so what's the incentive to buy parts of unknown provenance on eBay or the like?

I ask not being a hardware guy myself, so genuinely curious, as I've heard stories like this before.

Again, fantastic overview of the chip, though. I learned a lot.

[Edit: spelling]

[janekm]

That is unknown providence too. If you want to be sure of getting an original chip, you need to buy it from one of the official distributors as recommended by the IC vendor, or one of the well-known distributors (Digikey, Mouser, Farnell, ...). The well-know distributors can have high shipping to some parts of the world, hence the appeal of ebay in some cases.

[joezydeco]

Funny story, I had a high % of a certain part that was causing rejects on the line. We traced the lot numbers with the manufacturer's help and...they had no information on the lot.

Now we had a big problem. Was counterfeit product getting into the mix? Our distributor claimed they were clean, the manufacturer claimed they were clean too.

Turns out that the manufacturer had temporarily moved production to a different plant during the Fukushima tsunami. There was some...confusion...during the move.

[chiph]

Dad worked for a firm that made tantalum capacitors, and one day the truck carrying the raw metal was hit by a train on the way to their plant.

Tantalum prices being the way they were, they had the workers out there along the tracks picking up the chunks of metal from the weeds, collecting the pieces in plastic bins.

It was sent back to the smelter to be reprocessed, but the temporary shortage caused real problems with their delivery schedules.

[IneffablePigeon]

You have to be having a bad day as a truck driver to be hit by a train.

[kens]

Thanks for the comments. I bought the parts off eBay for several reasons. First, I wanted the less common metal TO-3 package so I could open the chip with a hacksaw rather than nitric acid. Second, eBay parts are amazingly cheap: you can get 10 7805s for $1.33 from Hong Kong, shipping included. (Does anyone know how they can ship something that cheap?) Finally, since I'm cutting the chip open, I'm not exactly looking for quality :-)

[diogenescynic]

Most Chinese sellers use a service called Epacket to send small items to the US. Epacket is a trilateral agreement between USPS, eBay and China Post that allows Chinese sellers to send items to the US in bulk at a low rate. Even without Epacket, Chinese postage is a lot lower than in the US.

[Scoundreller]

I think there's more to it than that since the shipping is usually free worldwide, not just the US. I think most countries in the world have an agreement through the International Postal Union to pay by total weight for international packages, and the rate is low. In China/HK and some other places, they pass that low cost to the consumer, unlike the US.

[dewitt]

Thanks for the fast reply, kens! Those reasons make a lot of sense.

And thanks again for the article itself. Very much enjoyed it.

[michaelt]

Is the stuff from Amazon Marketplace sellers really any more reputable than professional traders on Ebay? In my mind they're about equal.

[reportingsjr]

Are you so sure that those are not counterfeit? Even the "reputable" suppliers still end up with bad parts. It has become quite a problem/hassle in the last handful of years. Especially in the military industry.

On to your question about why: There are hundreds of electronics parts that are fairly standard and if people paid that much for them they would need a lot of money. Many /most people buying on ebay do it as a hobby.

A quick browse on digikey shows that <40 cents is easily found for a 7805 (http://www.digikey.com/product-detail/en/NCP7805TG/NCP7805TG...). Ebay would be even cheaper.

[VLM]

One problem with that reg is its a 1A reg. There is a pin compatible LM323T which is rated to 3 amps and is only about a buck and a half. Its not just fatter bonding wires and wider traces on the die, the thermal resistance from junction to package is ridiculously lower... how'd they do that? Obviously I know the theory of how to do that, but how'd they do it electrically pin compatible. Its like someone introducing in 2014 a ford model T that is blueprint compatible with every other model T except this one has 500 horsepower, somehow. I'm professionally semi-impressed by the 323T product.

There is a huge problem in the marketplace right now with LM323K series regs (basically a 3 amp die in a TO3 "big transistor" mounting case). The problem is old video game systems (not home systems, but video arcade) and some other old appliances use them, so you could modify the heatsink and stick a modern LM323T (aka TO-220 package) or hot wire in a COTS switching supply, but it wouldn't look "stock" anymore. So the market is getting flooded.

Its "well known" among CPU collectors that when you get a (insert obscure CPU here) from China, you're not really getting that CPU, you're getting some random 40 pin DIP with repainted markings. The only honest and reputable seller I'm personally aware of in China who doesn't do this is utsource, the stuff they ship actually works.

Its bad when they take a random chip like a 16550 or 8255 and remark it as a Z80 or 8086 for the collectors, but its actually worse when you really do need a 10 MHz rated Z80 or 6502 and you're sold a remarked 2 MHz part which kinda sorta sometimes works. Or if you want a real PITA some of the repainters are fairly ignorant and will ship repainted 6809 for 6809E and vice versa. Or another hilarious one, not all 6502 are pin compatible so you get a WDC product repainted to be sold as a rockwell product, which again doesn't work a lot of the time.

No, ebay in 2014 is not really fun at all for a retrocomputing enthusiast or whatever you call it.

I guess the closest HN sports analogy would be ebay is flooded with collectors items claiming to be the 1790 world series collectors plate or the 1925 football superbowl.

If you're just trying to regulate 600 mA for your rasp pi or whatever its no big deal but its a hassle for repair/restoration of old equipment.

[kens]

I took a look at the LM323 datasheets out of curiosity. As with the 7805, there are multiple designs that are very different. ST Microelectronics' LM323 has almost the same circuit as the LM109/7805, with a bandgap reference. Motorola's LM323 is similar to the LM340, with a Zener reference and a comparator. So you have two LM323 chips that use not just different circuits but fundamentally different physics to regulate the voltage!

As for how the LM323 supports 3 amps, the datasheet attributes it to "new circuit design and processing techniques". I'm tempted to open one up and see what's different from the 7805 (I'm guessing a bigger output transistor), but I've already got too many chips I want to look at.

[tdicola]

Price. You can find lots of cheapo regulators for pennies each: http://www.aliexpress.com/7805-voltage-regulator_reviews.htm... However you usually get what you pay for so it's worth getting a genuine part.

[cushychicken]

I tend to think of buying electronic components off of eBay as a form of low stakes gambling. If it shows up and works, you just got a killer deal. If it didn't, well, it was only $2.

[rasz_pl]

This Amazon supplier sell cheap Chinese trinkets, he probably has his own ebay store too and is based in Taiwan/Shenzhen.

[kjs3]

Habit? That said, many (most?) Amazon marketplace sellers are eBay sellers as well. I don't really think Amazon is "safer".