Home Forum Hardware DIY KIT1 v102 – Unit voltage on GM tube is too low

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  • #3044
    tuxik
    Participant

    Hello,

    recently i soldered unit on custom PCB and i am not able to tune voltage at GM tube – there is only 250-270V. I changed MPSA42, inductor, but problem is still here 🙁 On first stage of voltage pump is 127V (at second diode). Any idea where problem may be ?

    Thanks

    • This topic was modified 3 years, 7 months ago by Radu.
    • This topic was modified 3 years, 7 months ago by Radu.
    #3045
    tuxik
    Participant

    Photo of voltage on display

    Attachments:
    #3047
    Radu
    Keymaster

    I’ve seen this before, and the problem was related to the inductor. Try getting 2.2mH inductors from a different source, or ,as a quick dirty hack, put two 2.2mH inductors of the kind you have now in parallel.

    We might get over this by changing the frequency the inverter operates at – drop me a mail so I can send you a test firmware that uses a lower frequency (that might get noisy).

    #3053
    Radu
    Keymaster

    I also sent you by mail versions of the firmware configured for lower inverter frequency (down to 6.5KHz). Please test them and let me know if it helps.

    #3679
    jon
    Participant

    We tested a lot of transistors from different sources. The best Voltage/Duty ratio, we got it with the transistor (T2)
    http://www.reichelt.de/BF-299/3/index.html?ACTION=3&LA=446&ARTICLE=5464&artnr=BF+299&SEARCH=bf299
    BF 299 :: Transistor HF NPN TO-92 300V 0,1A 0,625W
    and
    http://www.reichelt.de/L-XHBCC-2-2M/3/index.html?ACTION=3&LA=446&ARTICLE=138556&artnr=L-XHBCC+2%2C2M&SEARCH=2.2mh
    L-XHBCC 2,2M :: Festinduktivität, axial, XHBCC, Ferrit, 2,2 mH

    best regards.

    #3682
    Radu
    Keymaster

    Perfect, thanks for the update!

    #6866
    tuxik
    Participant

    Hello all,

    i have build another uradmonitor, but problem with low voltage is here again (same as on first piece 3 years ago) – and voltage is extremely low.

    I lowered down frequency of oscillator, but no change occures.

    Some ideas ?

    Thanks,

    #6879
    tuxik
    Participant

    Sorry, my failure 🙂 Two of transistors was misplaced, everything is now ok

    #6887

    Hi Tuxik,

    Good to hear you got the KIT running now!

    Just as a reminder to others: One can NOT measure the HV directly with a DMM (multimeter), because the load resistance of a DMM is usually way too low (ca. 10 MOhm). If one touches the geiger tube electrodes with the DMMs cables, it would load down the HV significantly and lead to totally wrong results (reading way too low).
    Only the shown HV value of the KIT itself is to be trusted here.

    Cheers,
    Wolferl

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