"robb" wrote in message
...

"Tom2000" wrote in message
...
On Tue, 6 Nov 2007 07:34:53 -0500, "robb"
wrote:



there was no obvious visual evidence of any smoked parts that
i
could see , only the middle busman fuse was blown after the
short

and that seemed to be related to power going to the L298

thanks for all the help,
robb


Tough problem with all the ICs soldered in.

Chances are that the 32 volt supply is only used for the L298s,
as you
suggest. It also appears that you can unsolder these without
damaging
any other parts on the board. (Even if you have to cut them
out,
they're still available and easy to replace.)

If your short doesn't disappear after pulling the 298s, try
unsoldering any of the caps near those chips.

Leave unsoldering any ICs as your very last resort.

I'm now bowing out of this discussion and leaving it to the
experts.


Thanks Tom,
i really appreciate any comments and help

i unsoldered one of the L298 and it has no shorts so now the next
then i will do a trace of the 5V lines until i can learn
something usefull about the interconnections.

i hate working blind and re-tracing things when i could just look
on a schemat.

so thank you ,
robb


If you have a photocopier or flatbed scanner available to you, and the board
is not too big, I sometimes find it helpful, where no schematics are
available, to scan and print out the underside of the board, then take a few
minutes to draw on an overlay of the major components. Coloured felt tip
pens or highlighters can then be used to trace round critical signal and
power tracks. Makes it a lot easier then when metering for the problem. I
have found a digital ESR meter - such as the Dick Smith - which is capable
of accurately measuring and displaying very low ohms, can be useful for
tracking down dead shorts on rails that go all over a board.

Arfa