Ed Fair posted in an answer in anot 4

[gargouille]

Ed Fair posted in an answer in another thread that there's a way to diagnose a CPU with a logic probe.
How is that done?

 

[Snickle]

A list at

http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q="logic+probe"

shows several options about the device that electronics technicians use. Maybe that is what Ed Fair is referring to, but I couldn't find the note to determine for sure.

 

[edfair]

You have addresses and data running all over a M/B. You hook a logic probe to power and probe with it on the available address lines or the data lines (I use the BIOS chip) to make sure the CPU is really clocking addresses out and look at the data lines to make sure something doesn't have a data line pulled solid up or down.
This doesn't test all the CPU logic, only partial addresses and data, but it will keep you from pulling your hair out from a missing power good signal. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[gargouille]

Many thanks, Berton. I was googling it when I asked the question.

I know what the probe looks like and that they're cheaply acquired and one can even build them if you're into circuitry...I've found lots of schematics for them and was googling it and thought I'd ask where I know the answers will be tickety-boo!

I guess you don't use one?

 

[gargouille]

Aha, Ed! Thanks for replying. I guess you use the kind with the alligator clips...1 for power and 1 for probing?

So, IF I'm getting pulses with the probe set to TTL I know the processor is not likely failing?

The power good signal would be the 1st thing I'd find, 'cause I use an Antec power supply tester IF the machine won't boot.


(Mudd, you devil, you gave Ed a star before I could get
here!) Well, have another, Ed.

 

[mudskipper]

Edfair-Thanks for the good info! I have not personally used one and was also curious about it. All of my co-workers that I asked about this grumbled something like, "a what?"

...So much to learn ;-) Mudskipper
___________________________________________________________________________________

Groucho said it best- "A four year-old child could understand this! Quick! Run out and find me a four year-old child: I can't make heads nor tails out of this!"

 

[edfair]

NO, NEVER ALLIGATOR CLIPS. Them suckers will short things out and fry a M/B in nothing flat.
Get one with long power leads and put a clip test hook on for both leads and use one with a test probe point. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[gargouille]

You mean I can't just use a straightened-out paper clip?
LOL
Just kidding around...and thanks again for the most excellent tech advice!

 

[smah]

Getting off topic - this discussion is starting to remind me of something that happend to my roommate in college. He was studying electronics engineering. His stereo amplifier died, he diagnosed the problem, installed a new amplifier chip, then started probing to test it. A couple of seconds later - WAP, time for a new amplifier chip. The moral: be very careful probing around electronics, some of those connections are very close together and stay away from the coffee beforehand.

 

[mudskipper]

BAH! Don't worry about being off topic when illustrating such a good point! Safety first. That is, unless I gonna get a good laugh out of it! ;-) And gargouille, don't start knocking paper clips!! Those are useful little buggers!!

Looking at some plans now...that little guy would be easy to build--I guess I have a project! Why buy one when you can sniff solder?! Mudskipper
___________________________________________________________________________________

Groucho said it best- "A four year-old child could understand this! Quick! Run out and find me a four year-old child: I can't make heads nor tails out of this!"

 

[mudskipper]

edfair- Thanks again for the info. Do you mind having your handle listed to the bottom of faq602-2731? Just wanted to give credit for the info that came from others, but only if you approve Mudskipper
___________________________________________________________________________________

Groucho said it best- "A four year-old child could understand this! Quick! Run out and find me a four year-old child: I can't make heads nor tails out of this!"

 

[edfair]

Paper clips are a good tool. Used one yesterday. Crimped an end down far enough to make a spade to release a molex pin. Worked as well as a scriber point. Nothing like being out in the boonies to activate the "mother of invention" mode.

Smah,
Nothing like frying some chips to make you careful.

Mudskipper,
Get one with at least 1" probe point. Trying to get to a chip between I/O slots is a royal pain with anything shorter. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[smah]

Another saying from the same guy was:

All electronic chips are made with smoke in them, once you let the smoke out, they don't work anymore

 

[edfair]

Feel free to credit, but I would change the logic probe section to say "use it to check for CPU clocking". Logic probes are not capable of testing the CPU.

Otherwise a very comprehensive writeup. I would have the builder pull all offboard coneectors except power at the start and use a screwdriver as the power on switch but that is probably an invitation for somebody to fry something else. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[mudskipper]

Thanks--I'll make the change on the logic probe (good point, btw) and try to work in the other. Mudskipper
___________________________________________________________________________________

Groucho said it best- "A four year-old child could understand this! Quick! Run out and find me a four year-old child: I can't make heads nor tails out of this!"