Kind of works...

Support forum for the mightyohm.com Geiger Counter.
http://mightyohm.com/geiger
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margin_of_error
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Joined: Sun Dec 30, 2012 10:58 pm

Kind of works...

Post by margin_of_error »

I just built my Geiger counter and when I turn it on I hear an extremely faint whine from the speaker. The LED lights, but it is very faint as well. When I rotate the VR1, it changes the frequency of the whine, but I never get any clicks or blinks.
I have tried re-soldering all of the connections and made sure the parts are all oriented correctly. I tried shorting the tube and it gives a faint click and the LED goes out, and this is the only way I have been able to hear any clicks at all.
I have also tried using different sets of brand new batteries. I do not have access to a volt meter.
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mightyohm
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Re: Kind of works...

Post by mightyohm »

Can you post some high res photos of both sides of the board? I'll take a look and see if anything obvious jumps out at me. If you can get a digital voltmeter somehow that would be super handy!
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mightyohm
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Re: Kind of works...

Post by mightyohm »

Hey there,

The component placements look good - I can't tell if you have the transistors in the right place, so double check that Q1 is the FJN3303 and Q2 and Q3 are 3904's.

Many of your solder joints look marginal and should be reflowed. You want to heat the solder joints longer after applying solder so that the solder flows all the way around the lead and covers the land pad. The solder joint should have a smooth "hershey's kiss" shape and not be dull grey and cracked or pitted.

I suspect that bad solder joints are causing your problems. I recommend heating up each solder connection and adding a small amount of solder, then leave the iron on the pad for 2-3 seconds more to let the solder flow more completely around the lead. A good quality soldering iron helps a lot here. Try this and see if it helps.

There are lots more soldering tips here:
http://mightyohm.com/soldercomic
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