Help Identifying three IC's

[Rusty]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

Thanks

Tim

 

[Eeyore]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

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

 

[Lord Garth]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

Thanks

Tim

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?

 

[Chris]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

Thanks

Tim

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

 

[Michael Black]

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.

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

 

[Phil Allison]

** GROPER ALERT !!!!

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

** 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

 

[Eeyore]

I assume you means 74S??? btw ?

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

 

[[email protected]]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

Thanks

Tim

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.

 

[Phil Allison]

<[email protected]

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.

** 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

 

[Eeyore]

<[email protected]

** 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.

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

 

[Phil Allison]

"Eeyore"

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

** 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

 

[David L. Jones]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

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

 

[Phil Allison]

"Rusty"

I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

** 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

 

[Chris]

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

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."

 

[Michael A. Terrell]

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

 

[jasen]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is?

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

I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

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

 

[Michael A. Terrell]

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

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.

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.

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

 

[Rich Grise]

Hi All,

Is there a machine which you can plug in a 16 pin IC and it will tell
you what it is/number is? I have a circuit board with three 74lS????
ics which have had the numbers sanded off the top and I need to replace
them as they are faulty.

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

 

[Matt J. McCullar]

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.

 

[Rusty]

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