Harshaw 8S8/2A-X

Scintillation crystals, PMTs, voltage dividers etc...
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Svilen
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Re: Harshaw 8S8/2A-X

Post by Svilen » 25 Mar 2017, 22:53

Hi Steven,

Do you mean replacing both resistors with a single 1M trimmer using it's 3 connections, or two trimmers just to have two independent variable resistors instead of fixed ones?
Svilen

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Steven Sesselmann
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Re: Harshaw 8S8/2A-X

Post by Steven Sesselmann » 26 Mar 2017, 17:45

Svilen,

Yes the two resistors are in series, so you replace both with a one 1M potentiometer connecting the swipe in the middle.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

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Svilen
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Re: Harshaw 8S8/2A-X

Post by Svilen » 27 Mar 2017, 08:03

Thanks Steven, it is clear now.

I'll change the divider resistors with metal foil ones, since I think these that I used are carbon resistors. I'll maybe get a better quality external sound card and will order some lead bars to improvise some fast and easy shielding just to test its effect. Lets see if this will reduce the background noise and I will post some results later.
Svilen

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Re: Harshaw 8S8/2A-X

Post by devilmastah » 01 May 2018, 05:13

Hi there,

first of all sorry for reopening this topic. I hope to get an answer to the pinout of this tube since i have the same :)
Its to bad the pictures are broken, i found some in googles image cache but the resolution is bad there.

Since my gammaspectacular is still on its way (cant wait!), i am trying to prepare my tube at the moment.
What i want to know is if the schematic i added is correct (this is what i was able to find out from different pictures).

All resistors are 1 megaohm and the caps 10nF

Kind regards,
Hendrik
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Svilen
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Re: Harshaw 8S8/2A-X

Post by Svilen » 07 May 2018, 08:52

Hello Hendrik,
Your schematic is correct and I guess this is my picture you were looking for:

Image

Greetings,
Svilen

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Re: Harshaw 8S8/2A-X

Post by devilmastah » 18 May 2018, 22:49

Hi,

thanks for the response :). Nice to hear that the schematic seems correct.
Less nice that my detector seems bad then. Oh well it was 10 bucks in a militairy dump store :')
I dont hear any pulses listening to the audio input at all.
Well at least i have a second brand new pmt tube laying arround so time to build my own detector.

Just orderd myself a nice 65 mm diameter 65 mm long NaI crystal (new old stock). So the waiting game begins all over again :)

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Re: Harshaw 8S8/2A-X

Post by devilmastah » 19 May 2018, 10:05

So, it seems to be working after all :)
I just went to the point of opening the 1100A up and there is a nice RAW output pin, attached that to a scope.
Seems that i get nice pulses at 1100 volt under that nothing. Only thing is that i hear nothing when going to my pc. Think ill try to play with the gain resistors of the 1100A

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Steven Sesselmann
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Re: Harshaw 8S8/2A-X

Post by Steven Sesselmann » 20 May 2018, 17:13

Hi Hendrik,

It would be unusual for the GS-1100A not to have enough gain, and with your 12M divider it should be fine.

Check the sound card and everything else before you start changing gain resistors, because once you increase the gain you also increase noise.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

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Re: Harshaw 8S8/2A-X

Post by devilmastah » 21 May 2018, 09:07

Hi Steven,

i found out it was a rather crappy usb soundcard that caused the problem once i made a cable for my combined headphone mic jack of the laptop.
Furthermore i have a question, i have been playing with the values of capacitors and found that if i increase the capacity i get a LOT more detections (from 10 cps to 350). Can anyone explain how this works and what the impact of playing with these values is?

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