Logic analyzers - are they worth it?

Tornadoboy

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There's always a number of cheap HP logic analyzers on Ebay and I've been tempted to get one, are they worth it to a newb? What exactly to they do? If I understand it right they'll record the logic pattern on each pin of the probes and lay it out on the display so one can scroll through it, which could be useful to me as I try to figure out a number of screwed up but worthy PCBs sets I have.

But I'm no electronics genius, so am I wasting my time with something that's probably too over my head? Or is it a piece of equipment I might be able to grow into? For what I've seen I can probably set myself up for under $100.
 
What tools do you already have in your arsenal? As fun as logic analyzers can be, I'm not sure how practical they are for this hobby (esp. if there are other basic tools you don't already have - multimeter, logic probe, solder/desolder station, etc).

As far as usage, the main purpose is to monitor a batch of signals simultaneously. These can be either unrelated signals (in which case it's more of a convenience thing), or related signals like address or data busses. Usually for the latter to be useful, you would have to understand how to decode the bus cycles in order to identify failures.

LeChuck
 
The only thing a logic analyzer will show you is a clean representation of a signal (or two or three or 40). I rarely use mine, however, I have used it to find a problem I couldn't find with all my other gear.

I'd put a good soldering iron, logic comparator, and basic o-scope before a logic analyzer.

If you do decide to get one to play, the gotcha with the cheap ones are that they're usually missing the clips to connect them. These clips can go up as much as $5 A CLIP. I got lucky and found my analyzer for $35 and it had 7 clips laying in the bag...not bad and a good start. Also make sure all the pod cables are there as well..they clip onto the pod (box at the end of the cords) and provide the little leads to go to the ICs (where the clips connect).

logic-analyzer.jpg


The above pic is a usb adapter but it looks identical to what the old models have, and usually they have 2-4 of these. The moral is that its not really "that" necessary for basic repair, but if you decide to get one, make sure it has enough cables/clips to have some fun with.
 
I have a logic analyzer that I got for cheap on ebay. It is a fun toy to use while messing around with arcade boards. Unfortunately, for repairing boards you're better off with a logic probe, schematics and some knowledge of digital logic. Also, a logic comparator is a great tool to quickly find bad chips. You'll also want an oscilloscope to trace signal paths.
 
I agree with Orion and music man.

First a good quality soldering iron is a MUST. How are you gonna change parts without it? Next a good logic probe and a scope. If the signals are there but very dirty it may pose an intermittent problem and that is one of the hardest to track down. Before I would consider a logic analyzer I would get a good eprom/prom programmer or maybe a re work station.
 
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