counter stopped during a measurement
Posted: Mon Jul 18, 2016 1:11 pm
Hello MightyOhm,
I built one of your Geiger Counter kits and it worked fine for a while, but then it just stopped. The batteries seemed low (2.6v together), so I hooked the circuit up to my power supply at 3.00v. (I tried to be careful with the power supply, but the only way that I can think of that I could have fried this thing is by powering it with 5v instead of 3v.) It didn't work for about a minute, but when it started clicking again I figured that it just needed to warm up. It seems to work, but I know that something is wrong because it no longer responds to a radiation source that made the counter go crazy before. Also, there is no whine at startup, shorting across the tube clips does nothing (with or without the tube), and adjusting the potentiometer has no apparent effect either.
I tried all of the recommendations in your troubleshooting post (checking for correct placement of all the parts, reflowing my solder joints, etc.), but none of them seemed to help. I also read some other posts about similar problems where you asked for voltage readings, so here are my voltage readings between pin 3 of the pulse header and the specified point:
pin 1 of pulse header: 3.001v
TP1: 2.861v
TP2: 2.764v
U1 pins:
1: 0.000v
2: 2.266v
3: 0.001v
4: 0.021v
5: 1.854v
6: 0.000v
7: 0.000v
8: 3.001v
Removed U1:
U1 pin 4: 0.023v
TP2: 2.764v
With U1 removed, shorted U1 pins 3 and 8:
U1 pin 4: 0.052v
TP1: 2.875v
TP2: 0.859v
left leg of R8: 0.865v
All measurements were taken with a Fluke 175. I could only find input resistance (50 MegaOhms), but maybe you would have more luck.
http://en-us.fluke.com/products/digital ... #resources
Any idea what I can do to fix this thing?
Thank you
I built one of your Geiger Counter kits and it worked fine for a while, but then it just stopped. The batteries seemed low (2.6v together), so I hooked the circuit up to my power supply at 3.00v. (I tried to be careful with the power supply, but the only way that I can think of that I could have fried this thing is by powering it with 5v instead of 3v.) It didn't work for about a minute, but when it started clicking again I figured that it just needed to warm up. It seems to work, but I know that something is wrong because it no longer responds to a radiation source that made the counter go crazy before. Also, there is no whine at startup, shorting across the tube clips does nothing (with or without the tube), and adjusting the potentiometer has no apparent effect either.
I tried all of the recommendations in your troubleshooting post (checking for correct placement of all the parts, reflowing my solder joints, etc.), but none of them seemed to help. I also read some other posts about similar problems where you asked for voltage readings, so here are my voltage readings between pin 3 of the pulse header and the specified point:
pin 1 of pulse header: 3.001v
TP1: 2.861v
TP2: 2.764v
U1 pins:
1: 0.000v
2: 2.266v
3: 0.001v
4: 0.021v
5: 1.854v
6: 0.000v
7: 0.000v
8: 3.001v
Removed U1:
U1 pin 4: 0.023v
TP2: 2.764v
With U1 removed, shorted U1 pins 3 and 8:
U1 pin 4: 0.052v
TP1: 2.875v
TP2: 0.859v
left leg of R8: 0.865v
All measurements were taken with a Fluke 175. I could only find input resistance (50 MegaOhms), but maybe you would have more luck.
http://en-us.fluke.com/products/digital ... #resources
Any idea what I can do to fix this thing?
Thank you