RE: Asteroids/Asteroids Deluxe

Yup! Shorting like this is a last resort.

But, on the other hand, not really. If you have a short and you limit the
current to it, it'll just pull the voltage down as it gets hot until that path
fails. Then, there's no short, so you'll be left with a 'working board' which
will immediately start drawing the correct amount of current.

I've never used one, but I would guess that the professional bits of kit would
charge a big capacitor and then discharge it across the unit under test for.
This would give a determinable voltage/time curve 'dose' to the system.

I guess you'd only have a problem if you had a crap power supply that would
bounce around 5V on startup and pop stuff. But then again, this is exactly
what happens at bootup anyway, where the resistance is momentarily zero and
thus current is maximum of the PSU.

I suppose what COULD happen is that if the component that has the short has a
greater current capacity than the PCB tracks/soldering then these will burn up
first. (Which is what happens on a brand new board where the track is
shorted.) I would guess, though, that you'd have a seriously buggered
component to do this and running your hand over the components would soon tell
you which one it was.

Remember that all the power running through the short has to go somewhere -
heat (or light too if it's really spectacular!)

I've never buggered anything up fixing a PCB this way.

BUT DON'T TAKE MY WORD FOR IT. Ask several others!

Phil.

-----Original Message-----
From: owner-vectorlist@synthcom.com
[mailto:owner-vectorlist@synthcom.com]On Behalf Of Evrovski, Andrew
Sent: 23 August 2001 21:27
To: 'vectorlist@synthcom.com'
Subject: RE: VECTOR: Asteroids/Asteroids Deluxe

I thank everyone for the information/assistance up to this point, but aren't
we risking the good components doing this as well?

Andy

-----Original Message-----
From: Phillip Eaton [mailto:phil@freedomprojects.co.uk]
Sent: August 23, 2001 17:14
To: vectorlist@synthcom.com
Subject: RE: VECTOR: Asteroids/Asteroids Deluxe

-----Original Message-----
From: owner-vectorlist@synthcom.com
.
.
I think there's a technique with using a large amperage 5v power supply to
destroy the short (look for melting/flaming/exploding chips) but I've never
tried that one myself. (Clay told me about this one I think).
.
.

------------------------

I've done this on a number of occasions with brand new PCBs that my previous
company makes in-house. I used a big Wier power supply with variable current
limiting.

Usually on new boards it's due to solder trace shorting under an IC on a
populated board that's been through the wave soldering machine, although new
dead ICs have been known, and they get REAL hot!

Phillip Eaton (Forth-79/D-Type/Flip-Flop)
-------------------------------------------------------------------
Tel: +44 (0)1536 268424/504434 Fax: +44 (0)845 334 8195
Email: d-type@phillipeaton.com Mobile: +44 (0)7775 726366
Web: www.phillipeaton.com
-------------------------------------------------------------------

---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.

---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Thu Aug 23 13:55:46 2001