It certainly is getting harder and harder to find any fresh "geigers" to sample and count with that fine unit of yours . . . what with the last surplus ones being of the Korean Conf. vintage. At least, it does look like you might have got yourself the very latest of that series. Do you have its schematic for my providing more in detail evaluation ? (I mainly remember the Victoreen mainstays. . . .but . a duck is a duck is a duck .) |
:I bought an RCA geiger counter (WF-14A) and I'm trying to restore it to usability. Some of the wires had been cut - but were accurately labelled and easy to restore... It looks this was done to facilitate replacement of a portion of the battery box - but was never re-wired (there's no trace of solder on any of the tabs). It came with an RCA-branded radium source. I have the filaments powered with D-cells and I'm getting the 135V from an ARBE - but it's not working. The three 1U5's test okay. I'm only getting around 300V to the probe - whereas it should be around 1KV. If I momentarily short the probe terminal, it will flash the neon indicator and "count" on the meter. I am getting around 135V on the cathode side of diode CR1 - but only 300-400V on the anode side (should be 1KV). Any suggestions???
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:Sir SAGE . . . . . . . . .
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:It certainly is getting harder and harder to find any fresh "geigers" to sample and count with that fine unit of yours . . . what with the last surplus ones being of the Korean Conf. vintage.
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:At least, it does look like you might have got yourself the very latest of that series.
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:With the 1U5's, two are being in the amp and indicating circuitry and the one of most import to you now, is the one associated with the reflex oscillator citrcuitry used in upping the voltage to the minimal 5-600 V ionization keep alive threshold of the detector tube.
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:Are there any aged electrolytics being used in that particular circuitry, or high value resistors, since HV seems to do a thing on those last items !
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:As well as any LEAKY caps . . . even the VERY slightest amount . . . . PARTICULARLY on the cap that is DC isolating to the GM tube and coupling into the amplifying electronics after it when passing a particle pulse.
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:The miniscule current level required by the detector tube in its quiescent state is in the high picoamperes on up into the very low microamperes.
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:Therefore any measurement attempts, will result in loading, such as to diminish the actual HI voltage level present, significantly.
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:Be that with the typical 11 megs of VTVM's /TVM / DVM or a 10x scope probe, while observing DC vertical displacemant on the screen of a scope using it in its DC coupling mode.
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:The only two things that come to my mind to use would be a Physics or Instrumentation labs electrostatic voltmeter.
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:Or in a more possible realm the use of a 50---100Kv high voltage probe and dump its reduced output into a 1 meg potentimeter load.
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:You then adjust its wiper to feed a DVM from wiper to ground so that the reduced voltage sample then can be adjusted to read out as a "calibrated" value when measuring a 135 V or so DC sampling from your Arby Burger III.
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:I real l l l l l y think that your present derived high voltage is actually much higher than you have metered.
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:Do you have its schematic for my providing more in detail evaluation ? (I mainly remember the Victoreen mainstays. . . .but . a duck is a duck is a duck .)
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:73's de Edd
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::I bought an RCA geiger counter (WF-14A) and I'm trying to restore it to usability. Some of the wires had been cut - but were accurately labelled and easy to restore... It looks this was done to facilitate replacement of a portion of the battery box - but was never re-wired (there's no trace of solder on any of the tabs). It came with an RCA-branded radium source. I have the filaments powered with D-cells and I'm getting the 135V from an ARBE - but it's not working. The three 1U5's test okay. I'm only getting around 300V to the probe - whereas it should be around 1KV. If I momentarily short the probe terminal, it will flash the neon indicator and "count" on the meter. I am getting around 135V on the cathode side of diode CR1 - but only 300-400V on the anode side (should be 1KV). Any suggestions???
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I'm trying to locate a better copy.... Another thought - how can I test the GM tube??? All else is futile without it.....
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:Sir SAGE . . . . . . . . .
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:It certainly is getting harder and harder to find any fresh "geigers" to sample and count with that fine unit of yours . . . what with the last surplus ones being of the Korean Conf. vintage.
:
:
:
:At least, it does look like you might have got yourself the very latest of that series.
:
:
:With the 1U5's, two are being in the amp and indicating circuitry and the one of most import to you now, is the one associated with the reflex oscillator citrcuitry used in upping the voltage to the minimal 5-600 V ionization keep alive threshold of the detector tube.
:
:
:Are there any aged electrolytics being used in that particular circuitry, or high value resistors, since HV seems to do a thing on those last items !
:
:
:As well as any LEAKY caps . . . even the VERY slightest amount . . . . PARTICULARLY on the cap that is DC isolating to the GM tube and coupling into the amplifying electronics after it when passing a particle pulse.
:
:
:The miniscule current level required by the detector tube in its quiescent state is in the high picoamperes on up into the very low microamperes.
:
:
:Therefore any measurement attempts, will result in loading, such as to diminish the actual HI voltage level present, significantly.
:
:
:Be that with the typical 11 megs of VTVM's /TVM / DVM or a 10x scope probe, while observing DC vertical displacemant on the screen of a scope using it in its DC coupling mode.
:
:
:The only two things that come to my mind to use would be a Physics or Instrumentation labs electrostatic voltmeter.
:
:
:Or in a more possible realm the use of a 50---100Kv high voltage probe and dump its reduced output into a 1 meg potentimeter load.
:
:
:You then adjust its wiper to feed a DVM from wiper to ground so that the reduced voltage sample then can be adjusted to read out as a "calibrated" value when measuring a 135 V or so DC sampling from your Arby Burger III.
:
:
:
:I real l l l l l y think that your present derived high voltage is actually much higher than you have metered.
:
:
:
:Do you have its schematic for my providing more in detail evaluation ? (I mainly remember the Victoreen mainstays. . . .but . a duck is a duck is a duck .)
:
:
:
:
:
:73's de Edd
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::I bought an RCA geiger counter (WF-14A) and I'm trying to restore it to usability. Some of the wires had been cut - but were accurately labelled and easy to restore... It looks this was done to facilitate replacement of a portion of the battery box - but was never re-wired (there's no trace of solder on any of the tabs). It came with an RCA-branded radium source. I have the filaments powered with D-cells and I'm getting the 135V from an ARBE - but it's not working. The three 1U5's test okay. I'm only getting around 300V to the probe - whereas it should be around 1KV. If I momentarily short the probe terminal, it will flash the neon indicator and "count" on the meter. I am getting around 135V on the cathode side of diode CR1 - but only 300-400V on the anode side (should be 1KV). Any suggestions???
::
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