Re: Vcc buss rails being pulled down.

I use a Bug Hound (Gen Rad GR 2220). Found it on ebay and it works great for
finding shorts without pulling parts out of the board or blowing them open
with a high current (plan B). IIRC Tom has the manual on ionpool if you want
to check it out.

On Sun, Oct 16, 2011 at 5:25 PM, Rodger Boots <rlboots2@gmail.com> wrote:

> The only reason I didn't suggest this earlier he is that 50 mohms is a
> pretty good short and you won't get much heat out of applying power do that.
> On Oct 16, 2011 5:23 PM, "Rodger Boots" <rlboots2@gmail.com> wrote:
>
>> I used to do something similar, you cool the board (or part of it) with
>> co2 or freeze mist, enough to frost the parts over a little bit, apply power
>> and see what defrosts first .
>> On Oct 16, 2011 5:18 PM, "Chris Brooks" <armis@pcdochouston.com> wrote:
>>
>>> Short of breaking out a milliohm meter, when I worked for a printer
>>> manufacturer and we had boards that had hidden shorts, we would use a sheet
>>> of temperature sensitive liquid crystal ( I think you can get sets of these
>>> from Edmund scientific still). Set the board on the bench, lay the sheet of
>>> liquid crystal over it, and connect the board to a variable dc supply.
>>> Slowly bring the voltage up. And the heat near the problem area will make
>>> the sheet change color. Was a pretty ingenious method my boss taught me.
>>>
>>> On Oct 16, 2011, at 4:38 PM, litterbox99@mchsi.com wrote:
>>>
>>> > I'm working on a Slot machine MPU, with
>>> > similar 74xxx components like our arcade
>>> > games.
>>> >
>>> > The Vcc buss is being pulled down to about 50mv.
>>> > The LM340T5 runs very warm, so were keeping the
>>> > power on time very low.
>>> >
>>> >
>>> > Besides removing the IC's one at a time (and
>>> > of course their not socketed ) is there a way
>>> > to ID which component is at fault ?
>>> >
>>> > We've removed the IC's that are socketed, and
>>> > checked for warm or hot components.
>>> >
>>> >
>>> > Todd
>>> >
>>> >
>>> >
>>> >
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>>

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Received on Sun Oct 16 19:16:55 2011