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Re: [CDV700CLUB] Re: CDV-700

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  • troglodite@aol.com
    In a message dated 5/28/2010 8:43:19 A.M. Central Standard Time, GEOelectronics@netscape.com writes: Correct on the HV Doug. I got caught up in the transition
    Message 1 of 34 , Jun 1, 2010
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      In a message dated 5/28/2010 8:43:19 A.M. Central Standard Time, GEOelectronics@... writes:
      Correct on the HV Doug. I got caught up in the transition of car radios from "tube" to "transistorized". Actually they had one or two transistors only, in the audio section. Tubes everywhere else but a special kind that needed only 12 V on the plates. That type of circuit was called a "starved circuit:. Anyway there was no HV in there to tap off of for your converter. How inconsiderate. I beat that by placing 4 ea. 45V batteries in the glove compartment, series wired. Theses lasted for years.
      George,
       
      You bring back a lot of memories. I started working at 14. I did TV and radio servicing. I worked after school throughout High School, and in the summers. I was the "Auto Radio Specialist" for several years. I learned the "position" feet over the back of the front seat, head under the dash. :-) Must have gotten pounds of dust in my face over the years. I replaced vibrators, 0Z4's and buffer capacitors endlessly. And I remember well the evolution, though it took place after I was working on car radios, but I did a couple of designs with those 12 V tubes. They were interesting, what we would call the screen was actually the plate, and the screen was the plate. :-) That was a transition phase design because Germanium transistors were still marginal in the RF sections of auto radios for several reasons.
       
      Regards,
       
      Doug Moore
       
    • troglodite@aol.com
      In a message dated 1/16/2011 8:51:30 P.M. Central Standard Time, peter@freytagfamily.com writes: Thanks for the help. I will check the choke. I did find the
      Message 34 of 34 , Jan 17, 2011
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        In a message dated 1/16/2011 8:51:30 P.M. Central Standard Time, peter@... writes:
        Thanks for the help.
        I will check the choke. I did find the modifications and they have not yet been done.
        If I can verify that the GM tube is okay I will work at restoring the unit.
        Any way to test the GM tube without everything else working?
        What are the two Transistors, and what can I use to replace them or at leat troubleshoot them?
        Peter,
         
        If you have trouble finding the zener diode or other parts for the OCD modification, let me know, I can send them to you. No charge except for postage. There is no way to test the GM tube without special equipment. For that matter, even determining if the High Voltage is correct tales a somewhat special meter, though your fingers work for an approximation. :-) The transistors are Germanium PNP type 2N404 or similar. They are readily available.
         
        You can convert the unit to use Silicon transistors, but it is a bit more work, and if this is your first GC, it is probably best you just get it going as-is. They are fairly reliable if you do the OCD modifications.
         
        Probably others will suggest different procedures, but first check to see if you have any High Voltage. You can roughly do this by using two fingers on one hand from where the probe cable connects to the board to the case. You will feel a little sting, no danger. If you feel nothing, you have no HV. If you DO have HV, then take a screwdriver and with the unit in the X1 position, touch the end of the screwdriver to the point where the probe cable connects to the board. Touching it a few times should produce an indication on the meter. If this test is positive, then the "guts" of the counter are working. All that is left is the GM tube.
         
        Regards,
         
        Doug Moore
         
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