"robb" wrote in message
...

"Jamie" t wrote
in message ...
robb wrote:

I have an idea for you.
get your self a low voltage auto tail light lamp.
use it in place of the fuse that blows. start disconnecting
things until the lamp glows dim or not at all.
this will allow you to keep the circuit on, you can then
track down some heat traces which won't be much..
actually, you'll be able to do a volt tracking using that
method..
You might have some logic issues that is causing current
to exist only when the circuit is fired up.


ok Jamie i tried this idea with a few compromises and tangents

I only had 110 v bulbs and lattern light bulbs (~ 6V) so i used
my lattern lightbulb and the lattern battery (showing 5.2 Volts)
as my power source

no components or tracks were wam enough to discern a change
after several applications of power with increasing time ....

so i inserted the milliAmp meter (the DMM) and that showed ~160
mA with the 6V bulb in series and note the bulb was not shinning
as bright as it could.

so i removed the bulb and i get ~428 mA without the bulb and the
only thing that gets noticeably warm (*but* no more than prior to
the ZAP) is the 8051 procesor

this same result occurs no matter where along the 5V rail i
apply/inject the 5V ....

so i am not sure what this means, maybe good news ??

thanks for any help,
robb

Well, I would have to say that it certainly indicates that you are not
chasing down any kind of permanent 'short' on your 5v rail. So now that you
know where the 5v rail comes off the end of the LM317 (was it ?), can you
disconnect it from that point, leave the fuses out of the 12 and 30v feeds,
and hook the unit back to line power, with a 5v fuse in place ? Measure the
IN, SET and OUT pins of the '317 to see what you get, and if you get a
correct 5v on the OUT pin, then hook it back to the rail that you
disconnected, which is then just the same as hooking your battery to it. I
would expect all to be well, and you to get exactly the same result as with
your battery.

Once you've established that the 5v is ok, take it's fuse back out, figure
where the 12v rail is regulated, and disconnect it in the same way. With a
fuse in the 12v feed, apply line power, and measure the regulator pins. This
may be another '317 set for 12v, or might be a 7812. If you have 12v
correctly on the output of the regulator, then connect it back up and see
what happens. If it stays ok, then put the fuse back in the 5v, and measure
both rails. Repeat it again for the 30v rail, which probably isn't
regulated. You will have to locate it's smoothing cap, find the piece of
print that carries the 30v away from this point, and into the board's
circuitry (clue : I wouldn't expect this rail to go anywhere other than to
the driver chips that you mentioned previously), and either find a link on
it that can be removed, or put a scalpel through it. Once it has been thus
disconnected, apply power with the 5 and 12v fuses removed, and measure the
30v at its smoothing cap. If it's there ok, refit the 12v fuse, and check
both rails again. If ok, fit 5v fuse and check all three rails.

Now assuming that you really do have a problem, at some point this test
procedure will go off the rails, and that's the point that we need to know
to be able to offer any *proper* fault-finding advice. How far had you got
when everything was proceeding to plan? What happened then ... ?

Finding faults on electronic equipment is something of an 'art', much like
any other trade or skill, but it is based on firm principles, and these
*must* follow a logical sequence (no pun intended - well, maybe a bit ;-} )
If you take time to stop and think about what the problem *is*, not what you
*think* it is, then a logical test sequence will usually suggest itself to
you. If you then follow that sequence religiously, and whilst you are still
learning, write down the results, it should guide you slowly and surely to
an end result, as your tests suggest dead ends and new branches. With
experience, that part of the procedure goes on in your head.

So just take a minute to STOP and then THINK. Try the sequence that I
suggested, and then STOP again, and EVALUATE what you have found. Good
luck with it d;~}

Arfa