Help to identify National 14 pin DIP

That is a 30 year old house numbered part. Try looking on the bottom. Sometimes the real part number is stamped there on custom labeled parts. Or contact the company that manufactured the unit.

You might want to look at the board, so as to see what might make sense.

When I had quad emitter/detector circuits to play with in the 80's we were using an LM339 quad comparator. If the circuit looks like that might be it (with one quarter out of use) then it's worth a shot. If the pinout would not work for a 339, then that won't be what it is...

Thanks. I looked up the pinout for that, but the power pins don't seem to be in the right spot for a LM339. Now I'm thinking it may just be a hex schmitt trigger. I buzzed out the lines to the header, and if pins 7 and 14 on the chip are power, then pins 1 and 2 on the header are the power connectors. Pins 3 and 7 are not connected to anything, and that leaves pins 4, 5 and 6 as outputs, and they're on pins 2, 4 and 6 of the DIP. I'll probably just put 5V on it and see what happens when I block the light paths. I feel pretty sure it's just either totem-pole or open collector outputs. Worst that can happen is I just have to build a new one from scratch. What I don't understand is why they would use a house part number on something like this. This is surplus equipment, I don't know who the original manufacturer was.

If the power pins are not stock then that should narrow down the possibilities - there are only a few TTL devices that don't have the kitty corner pins and if this is a 14 pin device there are only a handful...

Can you tell if it runs at 5V or some other voltage (TTL vs CMOS)?

John :-#)#

Some companies do that to prevent employee theft. Some did it so that the parts had their stock number marked on it. Others were screened for certain characteristics. Sometimes only one OEM's part would work in a design, and got a separate stock number. We had separate stock numbers for a number of ICs at Nicrodyne, where we used multiple OEMs for the same base part number. I qualified, or blacklisted several vendors while I worked there.

Sometimes a batch of house numbered parts were surplused with the real part number on the paperwork from whoever dumped them. Small companies try to shave every cent they can on material costs, and would gladly buy the surplus.

It keeps the customer reliant on the manufacturer. At the very least it means the parts come through the company so they get the profit, at worst they can raise the price and make more profit.

It makes things a tad more difficult for someone to copy. It's no different than some companies sanding off the IC numbers. Someone tracing out the circuit has to work that much harder to figure out the circuit, and if they don't find the IC through guess and such, then they can't copy the circuit. It doesn't really stop those who have enough knowledge, but it does keep out the simpler ones.

There was also a time when semiconductors weren't made as efficiently, so there'd be lots of failures or semifailures in a batch. Sometimes the manufacturer would put an official number on them, I'm thinking of the time when 64K dynamic RAM were new and there was a high failure rate, but it was limited to half the die. So they were perfectly normal 32K RAMs. I suppose in some cases they might just sell the batch to one company, with a house number, if the supply was such that a single company would buy it all up. I suppose then things like transistors might be offered ashouse numbered devices if they were out of spec, but a company that could live with the lower specs could make use of them. You don't want "bad" 2N706s to land in the hands of people who think they are full spec'd.

Michael

Long ago, I worked for AEL Microtel in Vancouver, the successor to GTE Lenkurt. We used pretty nearly all house-numbered transistors (metal cans back then). Some of them were specially selected parts, but it was mostly to keep the stock numbers straight.

Cheers

Phil Hobbs

IBM, too. Everything was house numbered and rarely did one group use parts from another. Many had very unique specs. One engineer I worked with spec'd an LF386 up to $30 each (put a tested limit on it recovering after being driven into the rails).

Back when I worked for Fairchild/Schlumberger ATE we never used house numbered parts. (But then again, maybe we did. Most of the chips we used had Fairchild numbers and logos on them ;-)

RAMs.

spec'd.

We don't use many house numbered parts anymore. The things are too damned small to print part numbers on them. ;-)

No, they can print them but all the good engineers & technicians are too old to be able to see them. Isn't that why IBM developed the process of moving individual atoms with a laser? ;-)

Well, there is that. Good thing someone invented the Mantis.

Laser? I thought it used electric fields.

It may have. All I saw was a bad news article that looked like it was written by someone at the sports desk, and they do know how to speel lazar. :)

It was originally done using a cryogenic STM (scanning tunnelling microscope). Writing the IBM logo in novel ways to get free advertising on TV was a popular sport in the Research Division.

Cheers

Phil Hobbs

Well, it was in a magazine, and not well written by their staff. :(