Power supply protection networks

No, they are fairly new. But they are semi-autos.

Looks like this:

Reels on the left, automated carousel in the middle.

They work great. We have some other stuff we use for BGA placement and rework, except that we've only ever reworked two BGAs: one, the engineer thought it was the problem, but it wasn't; the other had been placed 90 degrees rotated.

Why are packages usually symmetric?

John

Oh neat. Thanks.

Oh, yes, that is indeed tiny. Never seen a machine this small. The ones I dealt with had to be hoisted in place by cranes.

That is something I will never understand. It make no sense whatsoever.

I had a similar experience today when testing some pre-production prototypes from an assembly house. They reverse mounted a tantalum (normally they just reverse mount chips) which blew straight into my face. Suddenly I like wearing glasses. A pity my glasses have some extra spots now.

And why were DIP numbered

when they should have been

John

From 8-pin TO-5 days.

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Or to appease the groups that write from left to right and those who write from right to left?

Tubes were numbered clockwise as seen from below. That was extended to round TO cans. So I guess dips were done that way to keep the TO and dip pinouts the same. So we're stuck with 100 year old conventions.

John

I thought everyone had done this long ago.

There is no rhyme or reason to the values we stock (whatever has already been used. There are some huge gaps, particularly in the 6En

- 8En values. If I really need a new value the boss can splurge for the $8 reel. ;-)

I use Excel. ;-)

We need at least four matching resistors for the Howland. Cost is mildly important.

Kinda expensive ($2-$3 per amp) and we really don't need that sort of gain accuracy, though perhaps in the transhybrid...

Actually, yes. I guess both of us remember the time when there was the occasional IC that wasn't yet available in the "modern" DIP-8 and so you had to buy the TO can version for a while, bend the leads a bit squarish and just solder it in. I've done that. This would have been impossible had they changed to your numbering scheme above. So I guess there was a good reason.

Maxim makes stuff like this, listed among their digital pots for some reason...

The only problem being that they're Maxim.

LTC is rumored to be going into the resistor biz, maybe.

Digikey has the Vishay SOT-23 parts, but the prices are laughable.

Considered a flying capacitor thing?

John

The "only" problem. Isn't that enough?

Not yet, but I'm all eyes. I am considering a PsOC, but when they were here recently they dropped the BOM that the DAC is only ten bits. YOY would anyone do a 16-20 bit ADC and then only allow a 10bit DAC?

Both the "stagger" and the QWERTY layout on most computer keyboards date back to the mid-19th century.

I don't mind QWERTY, but the stagger is a pet hate. Unfortunately, non-staggered (or symmetrically-staggerd) keyboards cost a lot more and/or have the "6" on the wrong side.

Actually, I can't get the Perl thing to run on my computer, so I plan to write my own parts wizard in PowerBasic.

John

Could you actually write an Excel thing (not a program... a spreadsheet I guess) to hunt for resistor ratios with constraints?

John

John

And why were the power supply pins chosen to be 7 and 14? It's impossible to do worse!

Jeroen Belleman