Troubleshooting the GS-1100a?

[NateFromBryan]

Hi! Forgive me if this is the wrong place to ask about this!

I've just picked up a GS-1100A and must be doing something wrong but I'm not sure what!
My probe is a Hamamatsu R9420 with a 24x24x22mm LYSO array. The probe is connected to the GS by BNC, and the GS connected to the 'microphone in' on my computer using the cables provided. I've tried it on two different computers and once straight into a sound-system. In the image below I'd been capturing for over ten minutes, and had the GS cranked to 11. With LYSO I expect to at least see something at 201.8 and 306.8 keV...



Theremino gives similar results, saying 'no audio input.'
I took a fluke to the BNC connector and get good voltage, although ~50 less than expected (e.g. 6.5 reads ~600v, 7 reads ~650v, etc).
I've also determined from the noise that the signals are negative, so I've adjusted the height threshold to -1, but still get no legit counts. I can crank up the gain and get 'counts' from the noise, but not radiation.
Also, I went through the 'getting started' instructions in Theremino, and it seems pretty clear from the DAA software that I'm getting zero sound from the GS-1100a; there's no difference in signal from having it plugged in vs not.
There must be something I don't understand about the audio input, but I can't seem to figure out what! Any tips would be greatly appreciated.

[Sesselmann]

Nate,

Looks like you are not getting the sound through to the computer.

The GS-1100A comes with a 3.5 mm mono jack plug which connects to the line in port on your computer. Using a mono plug means we are only using the left stereo channel on the sound card (tip on the connector).

In PRA you should open the audio settings and make sure you have selected the left channel line in port. You can also open the Windows audio control panel in and make sure the line in volume is set high enough. You can also click on advanced settings and tick the box "Listen to this device" which should channel the clicking from the detector to the speakers.

From the picture above I see you have not ticked the box called "Use Shape tolerance" this should be ticked for spectrometry.

Try this and report back.

Steven

[NateFromBryan]

Hi, and thanks for the quick response!

I've tried the things you've suggested, but see no change. I've tried it on three different computers with two different external soundcards.
Here's a screengrab:



Here's the url for the above image if it's too hard to see in forum: http://i.imgur.com/FxaYq5N.png

If I crank up the gain in PRA and/or Theremino, I can get electronic noise to show up from the sound card (same with or without GS-1100a plugged in), but there seems to be no audio signal.

Thanks for your help!

[Sesselmann]

Nate,

Sorry hear it's still not working for you, looks like we have to dig a bit deeper. Do you have a Digital Volt Meter?

First of all check that there is a bias voltage on the BNC Connector, set the GS-1100A to 600V and measure the voltage on the BNC, it won't read 600V because your DVM is most likely not a high impedance meter, but it should read about 400-500 V

Next step is to check if you are getting any sound out of the GS. With the GS powered on and the GS connected to your sound card and sound channeled through to your PC speakers, you should hear clicks or pops on the speakers when you turn the voltage knob on the GS-1100A.

With those two steps confirmed you need to check the cable to your detector you can use a Multimeter to check for resistance.

If that passes, you need to look at your detector, is it wired correctly for combined HV+SIG ? The HV wire should go straight to the anode not to the capacitor.

Looking forward to hear how you go.

Steven

[NateFromBryan]

Hi,
- Voltage at the BNC was as you said: the multi-meter read slightly below actual values, but it definitely is working there.
- Plugging it into a sound system and cranking it up I just hear white noise which increases in volume as I increase the voltage.
- Continuity was good on the audio cable.
- I don't know about the wiring for HV+SIG because I purchased it with the voltage divider and bnc endcap already on it, but they recommended the GS-1100A for use with it, so I assume it would be wired properly. I can contact them to ask specifically though, if a problem there seems to be the most likely explanation.

Thanks again for your help!

[Sesselmann]

Nate,

Okay, so we know the HV is good, please try one last diagnostic for me.

Power up the GS-1100A, connect the mono audio cable from the GS to your PC Line in and channel the audio through to your speakers, then turn the voltage selector and you should hear amplified poPs in your lodspeakers as the knob switches.

This confirms that the GS preamplifier transistor is good, you can also check by touching the live BNC connector with an ordinary graphite pencil tip, and you should hear some crackle in the speakers as you do it.

Finally if all fails we might try to hook up to a skype conversation so we can isolate the problem, it's most unlikely to be a faulty GS-1100A as I can't recall it happening before but nothing is impossible.

Steven

[NateFromBryan]

Hi! It's been a while, but wanted to report back in.
I finally had time to sit down and troubleshoot again, and the problem ended up being much much simpler than I imagined. Honestly I feel like a fool!
The issue was that, for whatever reason, the mono pin didn't jive well with my stereo ports. Despite using several computers and two different usb soundcard things, they all had the same bad interaction. But it was a simple problem with a simple solution, so no worries now; system seems to be working fine!

Thanks again for all the help!

[Sesselmann]

Bryan,

Thanks for reporting back, and well done on identifying that problem. These kind of problems can be real tricky to find especially if you don't have the right instruments at hand for proper diagnosis.

Good to hear you have it working.

Steven