Thanks for the info guys. There’s good news and bad news.

The good news is that I now know what the problem is, and if I’m lucky (which
unfortunately history has shown otherwise), it may be easily fixable.

The bad news is that you guys were both right and wrong about it being a 7805,
not a 7905. You’re right because that is indeed what is supposed to be there.
You’re wrong because that’s not what’s currently there. When I posted this a
month ago, I was advised to remove the three suspect components (the voltage
regulator, a power resistor, and a cap near the bottom of the board) to find
what was causing the short. I did so and found the short (it was B52 between the
power resistor and regulator). I removed B52, which resolved the short, but when
I was putting the three components back, somehow I put in a 7905 instead of the
7805 (I’m still looking for the 7805 right now).

I guess it makes sense that it’s not working now. I don’t suppose that I can
expect it to work when I put the correct one back can I? Would having a 7905 in
there (while on) have killed the board?


--
Alec S.
news/alec-synetech/cjb/net



"Arfa Daily" wrote in message
...
That would be a 7 *8* 05 then ... Just a comment as the pinning is different
between a 78 and a 79. The board has a t least two layers as evidenced by
the nearby vias. Is there actually any voltage appearing on the output pin ?
If not, is there voltage on the input pin. If there is, is the device
getting hot ? There should be an output decoupling cap nearby - probably
around 1 to 10 uF - with possibly a 0.1uF across it. You should be able to
follow the print from those. It should be easy enough to 'pick up the trail'
from the 78's output pin with your multimeter set to ohms, anyway.

"Michael A. Terrell" wrote in message
m...
As Arfa said, it is a 7805, and the silk screen clearly shows
'I'nput, 'G'round, and 'O'utput. in the first photo. Use a digial
ohmmeter and connect one lead to the output terminal, and probe the
board to see where it goes.

I wrote:
I can see where the input voltage and ground pins lead, but the output pin
doesn
't seem to lead anywhere. Is it a layered PCB or am I missing something?

It makes sense that the output voltage isn't connected because the scanner
does
nothing when plugged in; the power LED doesn't even light.