[Tech] Tracking down a PCB short...

[guddler]

[ukvac] [Tech] Tracking down a PCB short...
After a few hours the other day of testing out all my Asteroids stuff, I had
a board that worked, one that played with very screwy vectors, three or four
that were DAADD (Dead As A DoDo!), one that chucked smoke in my face and
nearly caught fire (that was interesting!!), and one that has a short
between +5v and ground.

I haven't plugged this one in. I remembered being told that one had a short
when I got hold of them, but couldn't remember which one, so I just did a
continuity test on them all to find which one it was rather that
accidentally plugging it in and screwing anything.

SO, how do I set about finding out where the short lies?

Needle in a haystack springs to mind :O)

Any suggestions?

Guddler.

------------------------
Guddler's Arcade
http://www.guddler.co.uk

 

[LukeWells]

Re: [ukvac] [Tech] Tracking down a PCB short...
There are continuity testers that do this. You move the probes arround and
as you get closer to the short the tester emmits a higher pitched tone until
you get to the short point. Kinda like looking for treasure with a metal
detector

Sorry can't remember the name of these things. I'm sure RS and all the main
places will sell one

Luke

 

[guddler]

RE: [ukvac] [Tech] Tracking down a PCB short...
Aha! That sounds very much like an ESR meter (which was discussed a while
back when talking about testing caps in-circuit). If so then that's cool as
I have one winging it's way over from Holland soon!

Of course I will also check out the link to Mr Fromms article, as strangely
enough I now remember reading that in a distant past somewhere anyway.

Mind you, when I get the time to sit down and go through this is a totally
different matter...

Cheers,
Gudd.

 

[John Bennett]

[ukvac] Re: [Tech] Tracking down a PCB short...
Polar ToneOhm 500 series is what you need, there was a 550 on ebay
last week. I got mine off ebay for about £30 a year ago.

Used to use them when I fixed PC motherboards when they where worth
fixing (pre 90's). If you see one make sure you get the probes with
it as they are very expensive to buy.

There's a picture of mine in the workshop section of my website just
incase you come across one at a bootie.

cheers

Chris

http://www.muppzlab.co.uk



DATA Imported from archives: originally posted by muppzlab (chris@toselands.freeserve.co.uk)

 

[d-type]

RE: Re: [ukvac] [Tech] Tracking down a PCB short...
Altenatively, use my 'engineering' solution:

Get a BIG power supply, turn the current limiter OFF, and connect it up.
Any short there is will soon not be there.

Whilst doing this, touch all of your ICs (preferably with someone else's
finger) to find the duff one. They will generate a 'tone' for you.

I've used this method successfully several times where I once worked.

D-Type

>There are continuity testers that do this. You move the probes arround
and
>as you get closer to the short the tester emmits a higher pitched tone
until
>you get to the short point. Kinda like looking for treasure with a metal
>detector
>
>Sorry can't remember the name of these things. I'm sure RS and all the
main
>places will sell one
>
>Luke
>

 

[John Bennett]

[ukvac] Re: [Tech] Tracking down a PCB short...
Finding something that short a power line (expecially +5V) can take
long time before find the shorted part. And then why did it smoke up?
There is only one fault or a "chain fault"? Anyway another method (or
an additional method) to track down S.C. (short circuit) is to break
the power lines to locate the faulty "sector". It's time wasting but
it requires only an ohm meter. When the short is found it's important
do some reverse enginering to understand if other parts connected to
it would cause another sc. Bye Simone Berti (NVC285, Sync Bus
Controller)



DATA Imported from archives: originally posted by Simone Berti (myid.xtc@tiscali.it)