In 1977 at NCR, we used an electron microscope to study the thermal activity within an IC and on foil paths. The quality assurance team used the electron microscope to find and eliminate hot spots. Some IC's have windows and we could see which bits were ones and which were zeros. The bright spots were more electrically active. We could change the program task and watch the IC change dramatically.
I wager that this doesn't help you, but I found it to be an interesting technique worth sharing. -----Original Message----- Sent: Thursday, December 26, 2002 5:29 AM To: Multiple recipients of list CHIPDIR-L On Tuesday 24 December 2002 22:18, somebody wrote Thanks for the reply and the ideas, on which I have some comments. Sorry if I don't sound too enthusiastic. > > Technique one: Pulse your unit on and off at 1000 Hz. Probe every > node with a high gain FET input audio amplifier digital probe and > listen for anomalies. I can write software to do this - It's an idea. I don't have the fet amplifier, but I'll try a 'scope. > > Technique two: If the nodes are lined up like an IC, then swipe the > digital probe so it hits each node in rapid succession. This will > cause the digital probe to make a chirping sound. If any node is > drawing more current than the other nodes, it will color the chirp > sound at that node. I learned that this is called voodoo > electronics. This is impractical - and that's the worst of messers talking at this end :-/. It's a small smt pcb, not a xylophone! > > Technique three: Make a shielded test probe with two tiny points > less than 0.1 inches apart. Connect the test probe to a high gain FET > input AC and DC amplifier. The test probe shield should be grounded > at the end connected to the amplifier ground input only. The test > probe shield should not be grounded to the circuit under test. A > separate ground lead should connect the amplifier ground input to > common bus of the circuit under test. Connect the output from the > amplifier into a scope or meter. Poke the circuit board traces until > you find a voltage anomaly. The higher the current passing through a > circuit trace the higher the meter or scope reading will be. If I gather the substance of this correctly, you are telling me to amplify the voltage drop across the traces. Fine, except it's a four layer board, and those traces are in the middle. I may well try to amplify the voltage between devices if the worst comes to the worst. > > > > -----Original Message----- > Here's one to tease yourselves over. I have a board to fix and for > once, I do not know how to go about it. > > Good luck' > Jeffrey Meade > [EMAIL PROTECTED] -- Regards, Declan Moriarty. -- Author: Declan Moriarty INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Author: Jeffrey Meade INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
