voltage problem Geiger Counter

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bgrattan
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voltage problem Geiger Counter

Postby bgrattan » Sun Jun 17, 2018 2:05 pm

Hello,
I purchased a kit from Adafruit with SMB-20 and case. It seems to be picking up random radiation but the HV_Adjust doesn't seem to be doing anything--it works the same on both ends of the pot. I don't have a source to test it other than bananas which don't seem to do much.
Here are my voltage readings from new batteries (3.054 volts) Using a Fluke 87 III
U1 pin
1: 0
2: 1.59
3: 1.18
4: 2.91
5: 2.03
6: 0
7: .562
8: 3.054

Remove U1
4: .04
TP1: 2.95 (this seems off but maybe I'm not measuring it correctly--(ground to TP1)

TP2 to ground: adjusting HV with pot I get 167 -> 310 volts (no resistor being used)

Serial out from FTDI Friend:

mightyohm.com Geiger Counter 1.00
http://mightyohm.com/geiger
CPS, 0, CPM, 0, uSv/hr, 0.00, SLOW
CPS, 1, CPM, 1, uSv/hr, 0.00, SLOW
CPS, 0, CPM, 1, uSv/hr, 0.00, SLOW
CPS, 1, CPM, 2, uSv/hr, 0.01, SLOW
CPS, 0, CPM, 2, uSv/hr, 0.01, SLOW
CPS, 0, CPM, 2, uSv/hr, 0.01, SLOW
CPS, 0, CPM, 2, uSv/hr, 0.01, SLOW
CPS, 1, CPM, 3, uSv/hr, 0.01, SLOW
CPS, 1, CPM, 4, uSv/hr, 0.02, SLOW
CPS, 0, CPM, 4, uSv/hr, 0.02, SLOW
CPS, 0, CPM, 4, uSv/hr, 0.02, SLOW
CPS, 1, CPM, 5, uSv/hr, 0.02, SLOW
CPS, 0, CPM, 5, uSv/hr, 0.02, SLOW
CPS, 2, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 0, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 0, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 0, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 0, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 0, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 0, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 0, CPM, 7, uSv/hr, 0.03, SLOW
CPS, 1, CPM, 8, uSv/hr, 0.04, SLOW
CPS, 0, CPM, 8, uSv/hr, 0.04, SLOW
CPS, 1, CPM, 9, uSv/hr, 0.05, SLOW
CPS, 3, CPM, 12, uSv/hr, 0.06, SLOW
CPS, 0, CPM, 12, uSv/hr, 0.06, SLOW
CPS, 0, CPM, 12, uSv/hr, 0.06, SLOW
CPS, 0, CPM, 12, uSv/hr, 0.06, SLOW
CPS, 0, CPM, 12, uSv/hr, 0.06, SLOW
CPS, 0, CPM, 12, uSv/hr, 0.06, SLOW
CPS, 1, CPM, 13, uSv/hr, 0.07, SLOW

Could anyone comment on this? Maybe it's ok but I want to be sure. Thanks in advance.

Bob

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mightyohm
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Re: voltage problem Geiger Counter

Postby mightyohm » Sun Jun 17, 2018 9:24 pm

That all sounds fine. If I measure the HV test point with my Fluke 87 V alone (no resistor), I measure about 215V. This is when VR1 is properly adjusted for 400V as measured with a Gigaohm resistor in series with the DMM.

bgrattan
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Joined: Sun Jun 17, 2018 8:33 am
Location: Ashland VA
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Re: voltage problem Geiger Counter

Postby bgrattan » Mon Jun 18, 2018 4:08 am

Thanks, Jeff, if it looks good to you then I must be ok. Now I need to find a source of radiation to make sure I’m picking things up as I should. I’ll adjust my HV to 215 to agree with yours. Much appreciated and a very nice kit!
Bob

MarkDV
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Joined: Sat Dec 15, 2018 5:24 am

Re: voltage problem Geiger Counter

Postby MarkDV » Sat Dec 15, 2018 5:40 am

Explain how to adjust the voltage exactly 400 V using a multimeter? What is the measurement scheme? Need a high resistance resistor? How to connect it? :roll:

I am sorry for my English!

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mightyohm
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Re: voltage problem Geiger Counter

Postby mightyohm » Sat Dec 15, 2018 11:03 am

There's some information here:
viewtopic.php?f=15&t=487

MarkDV
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Joined: Sat Dec 15, 2018 5:24 am

Re: voltage problem Geiger Counter

Postby MarkDV » Sat Dec 15, 2018 7:31 pm

Thank. But the link does not work! http://ea4eoz.ure.es/hvprobe.html :?:

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mightyohm
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Re: voltage problem Geiger Counter

Postby mightyohm » Sun Dec 16, 2018 4:14 pm

There is an archived version of that page here: https://web.archive.org/web/20120626122 ... probe.html

KamEmith
Posts: 12
Joined: Fri Jul 26, 2019 7:20 pm

voltage problem Geiger Counter

Postby KamEmith » Tue Aug 13, 2019 2:01 pm

So i check all layout and all the voltage on powertube, so:
Pin 3 all tube 477v
Pin 4 all tube 472v
Pin 5 all tube -55v
Pin 6 all fube 474v

Bias on v2 v3 v4 48ma but on v1 33vwhat? I tried four time but is correct 33v...changing tube the situation is the same...on v1 i read always volt...

About hum it is decreased changing preamp tube but is always a lot and encrease opening tone pot

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