...
BTW - Those thermal imaging cameras can't be cheap...are there ones out there that don't require you to mortgage your home? Just curious...cause it makes sense they *could*
save you alot of time searching for a fault.
BTW - Those thermal imaging cameras can't be cheap...are there ones out there that don't require you to mortgage your home? Just curious...cause it makes sense they *could*
save you alot of time searching for a fault.
I just posted on Youtube, but I thought I'd mention it here. As others indicated on the video, you can see damage to one of the brown packages in the analog front end of the left most channel (when the BNC's are facing towards the bottom of the frame at 12:36-12:54.
BTW - Those thermal imaging cameras can't be cheap...are there ones out there that don't require you to mortgage your home? Just curious...cause it makes sense they *could*
save you alot of time searching for a fault.
But they're coming down! http://www.alpha-electronics.com/Items/10930/flir-i7-educational-package.html
Here's my two cents. I posted to the Youtube video, but finally decided to get an account here.
3.2V at 11A is 0.29 ohms. The resistance you were measuring was about 0.110 ohms at the DC power plug (I subtracted the 0.060 leads resistance). The resistance almost tripled when when you went to 11A. This is telling me the traces are heating up and increasing resistance. You might want to desolder the DC plug and check for shorts under it, and you might want to measure the voltage at the tantalum bypass capacitors when powered with this 11A. An ohm meter uses a small current to measure the voltage across resistors, and the changes in resistance is small. Imagine if the ohm meter uses 11A instead.
The resistance you were measuring was about 0.110 ohms at the DC power plug (I subtracted the 0.060 leads resistance). The resistance almost tripled when when you went to 11A.
But they're coming down! http://www.alpha-electronics.com/Items/10930/flir-i7-educational-package.html
AU$990 "educational" pricing.
http://www.flir.com/cs/apac/en/view/?id=56018
I'm an "educational" resource, surely?
But still, even at that price it's a tool that's hard to justify.
Dave.
video at 11:14 : you can clearly see the deformation of the pcb around the screw hole. Take an xacto knife and scrape that metal off the top and bottom layer. then carefully scratch the fr4 away.. if you hit another plane : peel the plane away as well...
i have fixed an agilent scope once. they used long smetal standoffs from the board to tthe case. the case got thumped exactly where there was a standoff. this compresses the board enough that it actually permanently dented the board around the hole. there was a short between planes. by peeling off the pad of that hole i managed to get rid of the short. i also rpelaced the metal standoff with a nylon one ( as the internal 5 volts plane was exposed after peeling off )
scope still works five years later.
video at 11:14 : you can clearly see the deformation of the pcb around the screw hole. Take an xacto knife and scrape that metal off the top and bottom layer. then carefully scratch the fr4 away.. if you hit another plane : peel the plane away as well...
i have fixed an agilent scope once. they used long smetal standoffs from the board to tthe case. the case got thumped exactly where there was a standoff. this compresses the board enough that it actually permanently dented the board around the hole. there was a short between planes. by peeling off the pad of that hole i managed to get rid of the short. i also rpelaced the metal standoff with a nylon one ( as the internal 5 volts plane was exposed after peeling off )
scope still works five years later.
Dave,
Don't you just love all the 'free' advice you are getting (me included)?
-Joe
My second piece of advice is don't be afraid to use that exacto Knife and cut a surface trace or two. I use to do that when the voltage ran all over the board. I could then isolate which side had the problem. A second or third cut can isolate it down to a very small exact area
Mike beat me to it in that I knew you were wasting time with using that meter and trying to find milliohms of difference, that’s futile
and compounded by the fact that that you say the meter has a high resolution but as you stated it's accuracy is in question! So at those resolutions it begs the question what is it's repeatability of reading at the same point twice or more, it seemed to be really poor.
Which goes to the point that a lack of accuracy does not mean it will always be off by plus X or minus X but can drift all over the place.
My second piece of advice is don't be afraid to use that exacto Knife and cut a surface trace or two. I use to do that when the voltage ran all over the board. I could then isolate which side had the problem. A second or third cut can isolate it down to a very small exact area