TL866II logic test 74 series

[squigley]

I have searched (fairly extensively) and I can't find a similar thread..

I just bought a TL866II, from the legit website, and I have installed the software and got it running (full disclosure, using wine on Linux). It self tests OK.

I can stick random 74 series chips in it, and use the "Auto find" in the Device|Logic IC test screen. It detects them correctly, every time.

When I then select them in the list, and run a test, they fail.

This seems fishy. I did salvage all these chips, so they may be faulty, but I find it hard to believe they all are, and that it could auto detect them correctly every time, ie based on gates/logic, but then they fail when you test them specifically based on the model printed on them.

Anyone seen anything similar?

[squigley]

UI.

The demo thing seems weird.

[squigley]

OK, apparently I fixed it by creating this thread.

I have just retested 2 chips which detected and failed, and now they pass.

I changed the result by measuring it?

[squigley]

test

[squigley]

Attempting to continue correcting myself. got spam blocked..

[squigley]

then it worked.

[squigley]

OK, I'm going to blame solar flare, or gamma rays or something. I changed nothing except googled the problem, searched the forum, created a new thread, and now it's all working. Sigh. Failed successfully? Unfailed successfully?

[BrokenYugo]

Probably bad contact, mine throws a pin error reading/writing eproms if the chip is centered in the definitely not 3M zif socket, shifted to one side or the other and it works fine. I have used it once to confirm a bad gate in a 74 series chip, though it is far from the best, most conclusive tester for such things.

This video details the limitations.
https://youtu.be/gqbXM48bbOs

[ledtester]

...
I can stick random 74 series chips in it, and use the "Auto find" in the Device|Logic IC test screen. It detects them correctly, every time.

When I then select them in the list, and run a test, they fail.
...

Auto-detect may assume the chip is good to begin with. It can probably identify the chip (or narrow it down a lot) by the pattern of input vs. output pins (basically the pin impedance). It doesn't actually test the functionality of every gate on the chip - it only has to distinguish one IC from another.

Testing the chip, on the other hand, will exercise all of the gates on the chip.

For example, both the 74LS00 and 74LS08 have the same pattern of input vs output pins, but to distinguish the two you only have to test one of the gates.

[squigley]

Yeah, all of the "failed" chips I put back in, retested (in hopes of recreating the failed screen to add to the thread) and they all worked.

Now I have a couple which won't detect, and are probably fubar from my desoldering (I just bought a gun and was learning with it).

Maybe it just had to warm up a bit, or get threatened, I don't know.

[squigley]

Rather than spam a new thread.. I also have some SRAM chips to test.

Specifically a SHARP LH5116-10, which has a datasheet here: https://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/LH511610.pdf

It's not listed in the selection box, so I guess I'm out of luck on that.

[BrokenYugo]

Maybe I'm missing something but quick look isn't really telling me what makes a 5116 different from a 6116. They're both 2k 8bit CMOS sram with the same pinout, try testing it as a 6116.

And yes, desoldering DIP chips is not easy, at least not without a constant vacuum desoldering tool. Especially with plated through holes. Takes a lot of wick, flux, and some practice and patience to not trash the chip, board, or both.

[retiredfeline]

I used to desolder TTL chips from boards with a paint stripper hot air gun. Heat the back of the board until the solder melts, then whack the board on the edge of a cardboard box. Most chips, except the ones where they bent the pins inwards before wave soldering, fall out but you have a lot of solder splash on the pins to clean up later.

[Electro Fan]

OK, apparently I fixed it by creating this thread.

[squigley]

Testing them as 6116 worked properly. Thanks.