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Re: [mailstation] Re: mailstation 100 problem

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  • Eduardo Fuentes
    Hi CJ, I ve replaced the power supply for a new one (CIDCO original). The unit that is still working now passes all tests including DTMF and Modem. The one
    Message 1 of 10 , Mar 16, 2013
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      Hi CJ,
      I've replaced the power supply for a new one (CIDCO original). The unit that is still working now passes all tests including DTMF and Modem.
      The one that does not boot is still in the same situation, with the bridge on it passes all tests too. May be the old power supply burned the power on/off circuit.
      I'll try with AA batteries, but I would not bet on that works.
       
      I've found the schematics for a 250, I think it;s is very simmilar to 100. Looking at it seems U303(74HC74) or Q304 (2SJ244)  can be the culprit.
      I'll try to activate/deactivate the unit bridging G leg of Q304 to check if it works. I'll measure the voltage at G leg pressing On/off switch to see if the flipflop is working ok.
       
      Regards,
      Eduardo.
      PS: Thank you to be so kind to respond my questions.

       
      De: CyranoJ <cyranojones_lalp@...>
      Para: mailstation@yahoogroups.com
      Enviado: sábado, 16 de marzo de 2013 20:01
      Asunto: [mailstation] Re: mailstation 100 problem
       
      --- In mailto:mailstation%40yahoogroups.com, fuentesea@... wrote:
      >
      > I could make it boot.
      > I've put a bridge between 6V rail and the positive leg of C306.
      > I know that I'm a little out of spec for 5V components (I'm getting 5.6V currently). I'll use a 7805 tomorrow until I find a solution for this problem.
      > I think may be the 74HC74 may be faulty, because the key test pass OK for the on/off button but it does not starts when I press it without the bridge. With the bridge on when I press the button the device behaves as if it were turned off, keyboard don't respond any more but the screen is still on due the bridge.
      > Do you think that 74HC74 may be burned out or there are other things that may be bad in the on/off circuit?
      > Does anybody has the schematics?

      You said you had two units, both behaving strange.
      Are you using the same power supply for both?

      I would check that it is not faulty power supply before replacing
      any chips on mailstation board. Or maybe the line voltage is too low (brownout)?

      Perhaps the easiest way to to check would be to put the AA batteries
      in it, and see if that fixes it. Even if the regulator reads 6v
      with a meter, it might not be clean.

      CJ

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