GS-2000 Pro not working

[Schistad]

Hello,

I have a GSB-1525-PRO Gamma Spectrometry Kit, which has been working wonderfully for two years, but suddenly it stopped working.

I get no signal into the sound Card, just a little bit of noise. I have tried connecting a microfone to the sound Card and that workes fine. I have also tried to use different USB souncards, but none of them give a signal with the GS-2000 attached.

I use the Theremino software for spectrposcopy and the Intune software for pulse inspection. Previously I got nice pulses and gamma Spectra, but now I get absolutely nothing.

Is my sound Card driver defect or is it the PMT in the scintillation detector?

I have verified that the GS-2000 gives the correct (700V) output voltage.

What do you suggest that I do?

Kind regards,
Schistad

[Sesselmann]

Schistad,

Sorry to hear this, but fortunately you have done some good diagnostic work, so we should be able to narrow it down.

The first thing and easiest to check are the cables, Coaxial cable, audio cable, make sure they haven't developed a loose contact somewhere, once you have checked that I would go for the preamplifier opamp. It can and has on occasions failed, probably due to a voltage spike or something like that, bear in mind that we are putting high voltage and low voltage circuits in the same box.

If you open the GS-PRO by removing the 4 top screws that hold the lid, there should be a spare opamp circuit (LM358) taped under the lid.

The preamplifier is the one closer to the BNC connector, it's easy to replace, no soldering required, as it fits in a DIP8 socket. (note proper direction).

Let me know if this solves the problem, if not we have to dig a little deeper.

Steven

[Schistad]

Hi,

I have replaced the opamp, but the detector is still not working. I have checked the sound cable end it is OK. I have measured the voltage at the end of the cable to the PMT with a probe and it reads 700V. The signal I receive with high voltage on and a CS137 source just contains noise with occational random spikes. Disconnecting high voltage from PMT does not change the signal.
Screenshot from Itune:

Regards,
Bernhard

[Sesselmann]

Bernhard,

Thanks for trying my suggestion, sorry it didn't work.

Good idea to test with InTune, but I still don't have a clear diagnosis of the problem.

I guess my first test would be to try another BNC cable, especially if you have one of those thin RG-174U cables, we had some problems with a batch of those, and they were arching inside the cable. This would be an easy fix, as I could just send you a new cable. It's not good enough just to measure continuity, because it may only fail at high voltage.

Next step would be to try another detector (if you have one), just to eliminate the detector as a possible cause.

If you can narrow it down to either the GS, the cable or the detector, we can get you sorted out with a new one.

I put my betts on the cable ;)

Steven

[Schistad]

Steven,

I have tried replacing both the SHV (my detector has an SHV connector), since I use the and the audio cable. Still no signal. Connecting and disconnecting the SHV cable to the detector has no effect on the signal. Unfortunately I have no other detectors, so I cannot test the sound Card driver with an other PMT tube. I have tested the HV output, and that Works fine, but no signal except noise, from the GS box.

Bernhard

[Sesselmann]

Bernhard,

Thanks for your patience, I think the best option now is to send you a new circuit board. Please send me a PM or email me with your address details.

Steven