Re: Help Identifying three IC's

Chris wrote:

Chris wrote:
Rusty wrote:
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

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
.

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