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JB Haskins JB Haskins is offline
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Default help with circuit repair

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.