Maintenance PCB

[tsdomenichelli]

Hello,

I´m looking for equipments/devices for fast and accuracity fix PCB that we don´t have drawns/schematics or information about what it is used for.


Please, some of you has a laboratory with this kind of equipment that could share?

I search some equipments that uses Impedance curves to create basic condition information when the PCB is good and compare with other with malfunction.

Let me know if you know how this kind of equipment works and if has other kind of technology.

Thank you so much,

 

[IRstuff]

?? I don't get what you are asking. If you don't know what it's supposed to be doing, and you don't know how the fault is manifested, there will not be any correlation between power connection impedance and anything.

TTFN
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[ScottyUK]

IRstuff,

I think he's asking about some sort of reverse engineering equipment which attempts to determine the circuit of a PCB based on test results between PCB nodes. I've heard of this technology but have never had cause to use it or explore it - a PCB house which did some work for us a few years ago had something along these lines.

 

[VEBill]

Curve Tracers are test equipment where you connect a common and then start probing pins looking for a defective I-V curve on the scope's display. If an input or output pin is damaged, you'll have a fair to middling chance to identify and thus isolate the failure.

There are multiple brand names. I can't recall the model we have at work.

EDIT: Huntron 2000

Just Google 'curve tracer' and many will pop up.

 

[tsdomenichelli]

Thank you Scotty and VE1BLL,

This is what I´m looking for....

Thank you so much.

 

[tsdomenichelli]

Is it used for maintenance PCB in this days ? I´m thinking that one oscilloscope with X - Y function could do the same job .... what do you thinking? This tracer curves does it different ?

https://www.youtube.com/watch?t=27&v=s-mRtOIHqqM

 

[IRstuff]

Quite different. A curve tracer supplies a ramp in voltage or current and measures the other. Oscilloscopes are basically passive voltage sensing only.

Bear in mind that the cited type of instrument will only be even marginally useful if all you have are transistors and diodes on the board. They're basically useless for digital circuits where the faults are internal or non stuck-at faults.

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[VEBill]

Even with digital ICs, there will be a fraction of circuit failures where an input or output has been damaged, and this type of fault may be visible with a curve tracer. Of course, not 100%.

Experiences may vary with differing ratio of random internal component failure versus externally induced damage to an IO pin.

The Huntron used to be a popular instrument. The rise of ATE has largely supplanted manual troubleshooting for R&O, but requires detailed info on the circuit and investment.

 

[IRstuff]

Plus, with the lower voltage devices, something as brute force as a curve tracer has a very high probability of damaging somethings on a complex board.

To amplify VE1BLL's comment, while there is indeed a fraction of failures that can be attributed to the I/Os, the relative percentage of I/O failures relative to internal failures has grossly increased over time. In 1977, a 10" x 10" PCB might have had about 100 TTL SSI and MSI components, typically with 14 or 16 pins and maybe 10 internal components per pin. Today, a single FPGA with 400 I/Os might have 10 million internal components, which is a ratio of 25,000 internal components per I/O pin. I/O pins are much more susceptible to failure than internal components, but even allowing a factor of 100 higher failure rate, that would still put the internal component to I/O pin ratio at 250:1.

Another general comment; a curve tracer is also quite blunt as a diagnostic tool, particularly since it's really only useful for testing the diode characteristic of an output's drain or source junction, or an input's ESD protection diodes. If a junction is shorted, or an input gate is blown, then the I-V curve will look wonky. But, if the input metal trace is vaporized, there will be no obvious I-V curve error.

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[VEBill]

"I/O pins are much more susceptible to failure than internal components, but even allowing a factor of 100 higher failure rate..."

The 'factor of 100' might not be accurate. Perhaps the ratio varies between mil-spec vs industrial grade parts. Random internal failures from latent defects are exceedingly rare in mil-screened parts.

I agree that the utility of such curve tracers has diminished over the years, but many industries are still dealing in supporting older tech every day.

It's simply a tool in the tool box.

These days ATE is so quick and easy that it's the way to go. But you need to know what the card or box is supposed to do.

 

[tsdomenichelli]

Hello,

To use ATE equipments for house laboratory appear to be expensive. Do you know a user hand manufactory for ATE or recommend a way for this kind of task?

At least I saw from Digital Test company appear expensive.

 

[MacGyverS2000]

Look up Seica testers... we just got one in for reverse engineering bare boards. Pricey at around $200k+, but stick a board in before you leave for the night, give it a few inputs, and come back the next morning to a complete netlist for a multi-layer board. Pretty impressive...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

ATE is expensive to start.

Adding a connection adapter and code for the next UUT becomes relatively cheap.