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14. Solder the tube holder clips (J1 and J2).
These are the small metal clips. J1 and J2 are the furthest apart, this is for the SBM-20 Geiger tube, which is
longest. For other tubes, you can put the right clip into different positions.
I solder one lead of each clip, make sure it's straight, and then solder the other lead.
15. Solder the LED.
The LED only goes in one way. It will sit up a bit above the PCB. The long lead goes into the hole marked +, and
the flat spot on the side of the LED goes towards the other lead (just like the drawing on the PCB). Solder one
lead, check to make sure the LED is sitting straight, and then solder the other lead.
16. Solder C1, the large ceramic disc cap.
This one can go in either way.
17. Solder the battery holder (B1).
Make sure it's straight, solder the leads and cut off the excess (watch your eyes!). Pay special attention to the
negative terminal. It’s connected to a fat trace on the PCB, so you might need to leave the soldering iron on the
lead for a couple extra seconds before adding solder.
Insert the small screw into the hole in the middle. Flip the board over and install the small nut. You'll need a small
screwdriver, but you can use your fingers to hold the nut.
18. Solder the push-button (S2).
Important: If you purchased your kit with a case, use the long pushbutton that came with the case instead of the
ordinary (short) one that is included with the Geiger Counter kit!!!
The push-button can go in either way. No need to clip the leads on this either.
19. Install the Integrated Circuits (U1 and U2).
You will need to bend the IC pins inward slightly to get them to fit into the sockets. Be careful! You don't want to
push too hard and wind up with a pin bent and sticking out of the socket – maybe into your finger!
Make sure the notch and/or small dot on each IC goes towards the notch in the socket (on the left if you are
looking at the board with the text right side up). The ATtiny2313 has a large dot and a small dot on top, the small
dot goes closest to the notch (pin 1).
The TLC555CP goes into the socket for U1.
The ATTINY2313V goes into the socket for U2.
Handle these parts carefully, they are static sensitive.
20. Install the Geiger Tube.
Don't squeeze or push too hard on the tube, or drop it – it is very fragile.
Important! First, use a pair of needle-nose pliers to bend the tube clips apart slightly, so they aren't so tight on
the tube. Then carefully insert the tube.
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