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.

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

On 2/15/21 4:54 PM, Phil Allison wrote:
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


Thank you, that's what I have suspected as well.

JB Haskins wrote:
https://i.imgur.com/kSHzB0T.jpg

Unfortunately, I've never seen a schematic of this unit on the web even

Given the seeming simplicity of that board in your image (it appears to
be a single sided board) have you considered investing a moderate
amount of time into reverse engineering a schematic by following which
traces on the underside connect to which components from the top?

On 16/02/2021 8:08 am, JB Haskins wrote:
I have a small, handheld geiger counter made by a firm called RDX
Nuclear (model is DX-1).Â* 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.Â* Now, when the activation button
is pressed, all I'm getting is a constant tone.Â* Within the tone, I can
hear individual clicking as if it is still taking counts, but that's it.
Â*Also, the indication needle is pegged.Â* Here is an image of the top of
the circuit board:

Â*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.Â* Contacting RDX, all they
want to do is replace that tiny board... for $120.Â* So, if you hooked it
up backwards, what would you check first?Â* I did check the diodes and
they all seem fine.

**As Phil has stated, the 40106 is likely to be toast. For less than 10
Bucks and 20 minutes work, you could replace every semiconductor in the
thing.

--
Trevor Wilson
www.rageaudio.com.au

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

On 2/15/21 5:52 PM, Rich wrote:
JB Haskins wrote:
https://i.imgur.com/kSHzB0T.jpg

Unfortunately, I've never seen a schematic of this unit on the web even

Given the seeming simplicity of that board in your image (it appears to
be a single sided board) have you considered investing a moderate
amount of time into reverse engineering a schematic by following which
traces on the underside connect to which components from the top?


The last time I tried to do that, it turned out to be a disaster
although what I tried it with was a little more complex. Still, I might
give it a go with this one. I already ordered a replacement IC and the
transistors on the board- all are common parts and not expensive.
Actually ordered more than one of each since I own at least two of these
geiger counters.

On 2/15/21 6:47 PM, Trevor Wilson wrote:
On 16/02/2021 8:08 am, JB Haskins wrote:
I have a small, handheld geiger counter made by a firm called RDX
Nuclear (model is DX-1).Â* 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.Â* Now, when the activation
button is pressed, all I'm getting is a constant tone.Â* Within the
tone, I can hear individual clicking as if it is still taking counts,
but that's it. Â*Â*Also, the indication needle is pegged.Â* Here is an
image of the top of the circuit board:

Â*Â*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.Â* Contacting RDX,
all they want to do is replace that tiny board... for $120.Â* So, if
you hooked it up backwards, what would you check first?Â* I did check
the diodes and they all seem fine.

**As Phil has stated, the 40106 is likely to be toast. For less than 10
Bucks and 20 minutes work, you could replace every semiconductor in the
thing.


Quite true, even without a schematic, none of the parts are uncommon or
costly so ordered the IC and all the transistors. I got seconds because
I have at least one other of these units.

On 2/15/21 6:50 PM, JB Haskins wrote:
On 2/15/21 6:47 PM, Trevor Wilson wrote:
On 16/02/2021 8:08 am, JB Haskins wrote:
I have a small, handheld geiger counter made by a firm called RDX
Nuclear (model is DX-1).Â* 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.Â* Now, when the activation
button is pressed, all I'm getting is a constant tone.Â* Within the
tone, I can hear individual clicking as if it is still taking counts,
but that's it. Â*Â*Also, the indication needle is pegged.Â* Here is an
image of the top of the circuit board:

Â*Â*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.Â* Contacting RDX,
all they want to do is replace that tiny board... for $120.Â* So, if
you hooked it up backwards, what would you check first?Â* I did check
the diodes and they all seem fine.

**As Phil has stated, the 40106 is likely to be toast. For less than
10 Bucks and 20 minutes work, you could replace every semiconductor in
the thing.


Quite true, even without a schematic, none of the parts are uncommon or
costly so ordered the IC and all the transistors.Â* I got seconds because
I have at least one other of these units.



And I just got done putting a socket in there for the IC in case any
future accidents happen, the job should be simpler.

JB Haskins wrote:

==============

And I just got done putting a socket in there for the IC in case any
future accidents happen, the job should be simpler.

** Install a 1 amp diode in reverse across the batt connection while you are at it.

Only fools design such items with no reverse batt protection.



...... Phil

On 2/15/21 7:04 PM, Phil Allison wrote:
JB Haskins wrote:

==============

And I just got done putting a socket in there for the IC in case any
future accidents happen, the job should be simpler.

** Install a 1 amp diode in reverse across the batt connection while you are at it.

Only fools design such items with no reverse batt protection.


Good idea, thanks, will do that.


..... Phil