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Inexpensive Logic Analyzer for Lisa Troubleshooting - Suggestions Wanted

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AlexTheCat123:
I personally use the LA2016 and it works really well. It's a 200MHz logic analyzer with 16 channels, but they also sell other versions of it with different sample rates and channel counts if you need something a bit different. It comes in at about $160, so not as cheap as the Sparkfun one that @sigma7 linked to, but well worth the money in my opinion. The software is quite nice too, and you can download it and try it out before you buy the logic analyzer itself.

bmwcyclist:

--- Quote from: sigma7 on March 21, 2025, 04:47:24 pm ---

It looks like the list of supported ICs covers nearly all of the chips in the Lisa.

However, since the Lisa's chips are soldered in, removing them to troubleshoot a problem is (I think probably) more work than isolating a problem with in-circuit test equipment and removing only the primary suspects, at which point swapping them with new parts is practical.

So although potentially useful, I would prioritize some other equipment first for Lisa troubleshooting.

--- End quote ---



Could these be used to check the chips without removal?


https://a.co/d/hDUvoY0


.

sigma7:

--- Quote from: bmwcyclist on March 21, 2025, 10:10:50 pm ---Could these (IC clips) be used to check the chips without removal?

--- End quote ---

DIP clips (and the like) can be convenient for connecting to a chip in-circuit, but what you can find out from those connections depends on the equipment you are connecting to the clip.

Using them to connect a logic analyzer or oscilloscope can help reveal what is happening when the circuit is operating (or malfunctioning).

However, connecting a chip tester to a part still in-circuit is normally not useful as it can't tell whether the readings it is making are coming from the chip itself or the rest of the circuit it is connected to. Hence the requirement to remove the part to reliably test it.

In some circumstances one can locate failures by comparing in-circuit readings between a good board and a bad board, but this is not always possible and needs a greater knowledge of a particular circuit's components than typical troubleshooting.

stepleton:

--- Quote from: bmwcyclist on March 21, 2025, 10:10:50 pm ---Could these be used to check the chips without removal?

--- End quote ---

It would be nice to be able to clip a gizmo onto a chip and have it apply its own gentle probing to measure whether the chip was bad. Such a gizmo exists: the Huntron Tracker, is the example I know about. These devices seem to be somewhat magical and seriously expensive. As sigma7 mentions, they also seem to need a good board to compare against.

I don't know for inexpensive logic analysers, but for amusement's sake I can share that I bought a big old Pentium-powered 136-channel Tektronix TLA714 from eBay last year, and I've also got the giant 64-pin IC clip ready to chomp down onto the 68k "Texas cockroach" as soon as the need arises. This lumbering fin-de-siecle beast is good for recording a lot of signals for a short amount of time, and mine's been very useful for debugging an old PERQ workstation (an ongoing job!). But for troubleshooting a Lisa, it is probably preferable to have a modern device with fewer channels but a longer memory.

AlexTheCat123:


--- Quote from: stepleton on March 22, 2025, 06:08:54 am ---I don't know for inexpensive logic analysers, but for amusement's sake I can share that I bought a big old Pentium-powered 136-channel Tektronix TLA714 from eBay last year, and I've also got the giant 64-pin IC clip ready to chomp down onto the 68k "Texas cockroach" as soon as the need arises.

--- End quote ---

Yeah, I've also got a TLA714 as well as an HP 16702A, and they've got a whole lot of channels, but the memory depth is a huge limitation as you said. So I rarely end up using them, despite the fact that they have some really advanced features that the small modern ones lack, like the ability to decode instructions on a variety of different CPU buses. And the UIs can be pretty tough to use on some of the older ones too. But they sure look cool!

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