JB Haskins wrote:

=================
I have a small, handheld geiger counter made by a firm called RDX
Nuclear (model is DX-1). Unfortunately, a much younger family member
than I decided to try putting a 9V battery in it, but he put it in the
wrong way before I could intercept him. Now, when the activation button
is pressed, all I'm getting is a constant tone. Within the tone, I can
hear individual clicking as if it is still taking counts, but that's it.
Also, the indication needle is pegged. Here is an image of the top of
the circuit board:

https://i.imgur.com/kSHzB0T.jpg

Unfortunately, I've never seen a schematic of this unit on the web even
though it seems to be sold all over the place. Contacting RDX, all they
want to do is replace that tiny board... for $120. So, if you hooked it
up backwards, what would you check first? I did check the diodes and
they all seem fine.

** The CMOS IC is the most likely be damaged.


...... Phil