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by mightyohm
Fri Mar 08, 2019 10:23 am
Forum: Geiger Counter
Topic: General info
Replies: 1
Views: 9953

Re: General info

with batteries: 138g
without batteries: 116g

both include the case and tube. Removing the case will save about 60g.
by mightyohm
Fri Mar 08, 2019 10:20 am
Forum: Geiger Counter
Topic: Sensitivity Adjustment
Replies: 8
Views: 15225

Re: Sensitivity Adjustment

Try a SI-3BG tube - it's much less sensitive than the SBM-20 and there are lots of them on eBay. Alternatively you can place some shielding around the SBM-20.
by mightyohm
Tue Mar 05, 2019 5:56 pm
Forum: Geiger Counter
Topic: Sensitivity Adjustment
Replies: 8
Views: 15225

Re: Sensitivity Adjustment

Are you trying to increase or decrease sensitivity?
by mightyohm
Mon Mar 04, 2019 9:00 am
Forum: Geiger Counter
Topic: Sensitivity Adjustment
Replies: 8
Views: 15225

Re: Sensitivity Adjustment

I can think of a few ways to do this: Change Geiger counter tubes based on what you are trying to measure. Tubes with a larger cross section will be more sensitive. Tubes with a thinner wall or constructed with materials that pass more and lower energy radiation (like mica windows) will also be more...
by mightyohm
Sat Feb 16, 2019 2:33 pm
Forum: Geiger Counter
Topic: Powering Multiple Units
Replies: 1
Views: 10489

Re: Powering Multiple Units

I don't think this should be a problem. What is your power supply?
by mightyohm
Sat Feb 16, 2019 2:32 pm
Forum: Geiger Counter
Topic: Homemade GM tube
Replies: 7
Views: 20234

Re: Homemade GM tube

Antonio,

That is very cool, thanks for sharing an update on your progress!
by mightyohm
Sat Feb 16, 2019 2:31 pm
Forum: Geiger Counter
Topic: Geiger Counter not working
Replies: 6
Views: 16232

Re: Geiger Counter not working

Glad you got it working! Let me know if there is anything else I can help you with.
by mightyohm
Sat Feb 16, 2019 12:18 pm
Forum: Geiger Counter
Topic: Geiger Counter not working
Replies: 6
Views: 16232

Re: Geiger Counter not working

First, confirm that the voltage from pin 3 to ground is still 2.9V, and the voltage from pin 2 to ground is 0V. This is the issue - if pin 3 is stuck high, then pin 2 should be high as well. Measure the voltage across R5, D2, C3, and R9. Those voltages will help us troubleshoot what is going on. It'...
by mightyohm
Tue Feb 12, 2019 9:28 pm
Forum: Geiger Counter
Topic: Geiger Counter not working
Replies: 6
Views: 16232

Re: Geiger Counter not working

Can you post a high res photo of the top and bottom of the PCB?

Check the direction of D2 and make sure it matches the silkscreen on the PCB. Also check the solder connections around R6, D2, C3, R9, and U1.
by mightyohm
Fri Jan 18, 2019 1:25 pm
Forum: Geiger Counter
Topic: Homemade GM tube
Replies: 7
Views: 20234

Re: Homemade GM tube

no change