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High voltage is low
Posted: Fri May 18, 2012 2:58 pm
by akitchens
Just finished assembling the kit and not getting any clicks. Checked the high voltage at TP2 and am getting 167-315 volts at either extreme of the adjustment pot.
I believe this is too low for the tube to operate.
What would cause the voltage to be low?
I have already reflowed all solder joints and verified part placement according to the assembly instructions.
Any help would be appreciated.
Re: High voltage is low
Posted: Fri May 18, 2012 9:37 pm
by mightyohm
How are you measuring the voltage?
Unless you use a large (1 Gigaohm) resistor in series with your DMM you will get a false reading.
If you take a piece of wire and short across the tube, do you get clicks?
Re: High voltage is low
Posted: Fri May 18, 2012 9:57 pm
by akitchens
Well, I reseated the 555 timer and now sometimes I get soft beeps and clicks 1/sec.
Sometimes when shorting the tube I get beeps or clicks. And the LED stays on constant after shorting sometimes.
Other times it just sits there doing nothing.
Very erratic behavior.
Re: High voltage is low
Posted: Fri May 18, 2012 9:58 pm
by akitchens
I was using a Craftsman DMM rated for 500V to measure the HV.
Re: High voltage is low
Posted: Tue May 22, 2012 5:59 pm
by mightyohm
Do you know what the input impedance of your DMM is? Most likely it is 1 or 10 MegaOhms, too low to measure the HV supply used in the Geiger Counter kit.
If you are seeing erratic behavior, it's probably not a voltage issue, but more likely there is a bad solder joint somewhere.
Re: High voltage is low
Posted: Tue May 22, 2012 6:14 pm
by akitchens
OK I'll reflow everything and see what happens.
Thanks for the help.