On Tue, 28 Feb 2006 23:56:58 GMT, "Allen Crawford"
wrote:

I recently purchased a pro97 scanner in near new condition over the internet
through ebay. The item was
listed as having very low audio such as one has to place the speaker next to
his ear to hear the broadcast so I took a chance and bought it for 45
dollars. I got it in yesterday and it is totally new! packaging, all
accessories, books and not a scratch on it. Well. I unpack it and install
freshly charged (new) batteries and
I go to playing with it..first..a weather channel..sure enough, very low
volume even when cranked to the fullest
it is still at the same volume level. I went ahead and took out the four
back cover screws and examined the area
where the volume pot is soldered and took some readings. center tap is
about 2.1kohm and 200 k ohm on the non grounded side. (this is without power
applied)
in the area of the volume/squelch pot, are 3 tiny pots
and 3 test points...(this is all from memory as the scanner
is closed up now). I was hoping for a misplaced speaker magnet or something
simpler and the circuits are ungodly
miniature and even the audio amp chip is about the size of an op amp on most
regular size circuits. The doggone thing is so new looking, that it may be
swapped with a
newer one from radio shack (by swapping backplates) but I don't dare attempt
the dishonest. Anyway, any suggestions to resolve my dillemma...could it be
possible that I have a defective volume pot? No amount of regulation seems
to affect the audio at all. The channel
beep come through loud and clear but it seems that either
the preamp from the radio is set too low or the pot is defective/soldered
wrong. Of course, the possibility of
a bad IC has crossed my mind as well. Any suggestions?
No warranty so all I have is either a repairman or my good wits and some
knowledge to help correct the problem. Btw, the sqelch seems to work OK.

Your input would be greally appreciated,

Allen



Allen, I had a PRO-96 that had the *exact* same problem... I'm not
sure how similar it is to the PRO-97, so the following may or may not
be of any use... but might be worth a try, or may give you some
ideas...

Have a look at the picture at:
http://www.ninemoons.com/~daf/images/PRO-96.jpg

After trying all the obvious stuff, I found that very gently pushing
down on the edge of the circuit board (with a non-metallic object :-)
in the area outlined in red that the volome would increase
tremendously. It was quite touchy, and seemed to be fairly localized
to that general area. Volume would always return to it's previously
"barely audible" state when pressure was released. I suspected a
micro-crack in a solder joint or possibly one of the "plated-through"
holes. A "cold" solder joint was another possibility...

I removed the board and inspected both sides very carefully in that
area with the highest power magnifier I had on hand (an eyepiece from
a microscope...:-) Visual inspection didn't reveal anything, so I put
the board back in and tried it again with the exact same results.
This went on about 4 times until I finally got disgusted and drug out
my trusty soldering iron!

Having done a lot of bench work, I have a soldering iron with a tip
about the size of a ball-point pin. I wouldn't recommend doing this
with anything bigger, as it is very easy to overheat these SMT
components.

Using some high power reading glasses, I very briefly heated each of
the solder joints "to melting" in the general area outlined in red,
using no extra solder. (Very easy to use too much on these tiny pads!)

I did add very minute amounts of solder to some of the plated-through
holes until I could tell from both sides they were "soldered-through"

After putting things back together - VOILA! Normal sound levels!

The final test was when I could get no changes in the (now normal)
volume by pushing down in area that had been so touchy before.

Hope this helps...

-Dan
------

Disclaimer! I'm NOT responsible if you muck things up worse!!