Help Identifying three IC's

How do you they're faulty when you don't know what they are ?

I assume you means 74S??? btw ? I can recall an eprom programmer of old I once used that could identify 74 series but never seen one since.

Graham

Are they "belly branded"? That mean to inspect the underside of the IC first. Further, the top markings sometimes show when the packages is damp.

What is the device?

Hi, Tim. If you can get them out of the board in one piece, you should be able to do what you want. The device you're looking for is called a digital IC tester. This capability is also built into many of the older EPROM programmers. They were called "Universal" EPROM programmers. Both of these have the ability to safely test an unknown DIP package logic IC to determine if it's 74-series TTL, or 4000- or

4500-series CMOS, and give you the part number. They're pretty reliable, and won't damage the part.

The biggest hangup is that they don't test every conceivable possibility, especially the oddballs or single-manufacturer parts.. N.B.: Look at the docs to determine which parts it can detect.

BK Precision makes a digital IC tester, but it's a little expensive. I'd look around for an old EPROM programmer, or take a look at eBay. You should be able to pick one up for less than $100.

Good luck Chris

There were schemes in the old days, which amounted to comparing an unknown IC with known ICs until there was a match. Tedious, and of course if the unknown device was not the same logic family, it might damage things, and if the unknown device is defective, then you aren't likely to get a valid match.

Michael

** GROPER ALERT !!!!

** Yep - and the exact same machine will tell you the value of resistors that are burned to a crisp, the capacitance of caps that are dead short and the turns wound on a transformer with open windings.

A wacky looking guy named " Doctor Who" used to sell them out the back of a white Tardis van.

....... Phil

Re-reading that in another font maybe you mean 74LS ?

Anyway - some older eprom programmers had the ability to check out these parts. They'd have to be working ones of course !

Graham

When I was really desperate to identify a house-numbered IC, I removed the packaging to expose the silicon chips. Then I would inspect them with a metallurgical microscope. They often had the manufacturer's logo and the standard catalog part number easily readable somewhere around the periphery of the chip.

There are some nasty chemicals that will dissolve epoxy without hurting the silicon, but I just used brute force. If you do it this way, first get some practice on some other ICs.

** That is very hard to believe.

I must have opened hundreds of metal package ICs ( TO 100 etc) and transistors ( TO5, TO66 and TO3) and NEVER once seen a logo or number on the chips.

....... Phil

Not many ICs in TO3, TO5 or TO66 ! ( OK I know )

I broadly agree with you but I have seen some mfrs mask patterns with house logos.

Graham

"Eeyore"

** Try learning to read - Mr Eyesore !!

However, there ARE any number of regulator ICs in TO3 ( eg LM338K) and a few old ones in TO66.

I have a whole bin full of op-amps in metal ( TO5 size) packages:

741s, 318s, 301s, 308s, 310s, 1458s .....

....... Phil

How do you know they are faulty? If you were able to determine this then you either have a) another working unit to compare with, b) obviously fried chips, or c) schematics which show the operation, in which case you can figure it what the device is fairly easily, or at least narrow it down two a few possibilities.

If they did work you could have used a "Digial IC Tester", but seeing as that they don't work, you can't.

16 pins narrows down the "suck it and see" method to maybe 1/3rd of the TTL range :->

Dave :)

"Rusty"

** Rub a dub dub, my ICs have been scrubbed ,

I haven't a clue what they be,

Is one a butcher, a baker or candlestick maker ?

Chuck 'em out, stuffed - all three.

........ Phil

I believe I got my first "universal EPROM Programmer" from somebody in a Tardis back when the earth's crust was still cooling (although it was a blue police box -- I suppose they've fixed the Chameleon Circuit since then).

Phil's right, of course -- if the IC is dead, you can't read it with a digital IC tester. But it's very possible they're not all smoked. If your board only has three 74LS ICs, you might be able to get the ID on two of them, and then make an educated guess as to the third based on pin I/O and circuit functionality.

Or you could always find a known good board, and find out the part IDs from that one.

Good luck Chris

"That's the trouble with regeneration. You never know what you're going to get."

Or you could draw out the circuit and figure out what the IC functions are from the way the circuit is laid out. Not easy, but it can be done. Another method is to find the +5 VDC and Gnd rails, then remove the chip, power it up and use a weak pull-up resistor on the pins to determine the function. A lot of TTL chips had multiples of the same function, so you can determine what they chip is, then pick a replacement part.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

could possibly be done with a logic anylyser(sp?).

hmm all an alylyser will tell you is that the parts don't work.

If you can get a working unit you could try chips in it until you find working replacements for each part.

Bye. Jasen

If you'll suppky him with the schematic so he knows where to hook up the pods. If he had the schematic he wouldn't need to spend thoudsands of dollars on the analyzer.

That is a good way to destroy a working unit by randomly inserting a pile of chips hoping to find something that works.

Any more bad ideas you'd like to share?

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

If the chip is already faulty, there is no way any machine can read out what the chip used to be supposed to do.

You might just have to trace the circuit out and figure out what the chips do, and pick the right ones.

Good Luck! Rich

There are some PC-based chip testers that can do this; I use one at work often. But the chips need to be working, and must be physically removed from the circuit board and placed into the tester's socket. Even then, it's not always 100% accurate. It'll give you a good ballpark starting place. There are several instances of different TTL chips doing the same job and having the same pinout (such as 7404 and 7414), but the tester won't be able to tell the difference. It also won't be able to differentiate between standard TTL, LS, C, HC, and so on.

This is the tester's so-called "auto-locate" function. It can also test a TTL chip if you enter in the real part number, but even then it's not 100% accurate. I once placed a 7400 chip that had an input shorted to ground, and the tester thought it was good! (All test equipment will lie to you at some time or another.)

But there's a chance that the manufacturer may have printed the chips' part numbers on the underside of the chips. They do that sometimes, and whoever sanded off the numbers from the top may not have done so to the other side.

Thank you for all the feedback, I have ordered a LEAPER-1 off ebay and will test the ICs, hopefully they will report correctly.

Best wishes