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Grounding Stick. (Chicken Stick)

Discussion in 'General Technical Questions and Answers' started by GW1HIN, May 16, 2008.

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  1. GW1HIN

    GW1HIN Ham Member QRZ Page

    Hi,
    On my TS830, I want to work on the valve (6146Bs) section.
    Disconnecting from the 'mains supply' and waiting 10 minutes is supposed to discharge any HV from the capacitors etc, via the 'Bleeder Resistors', however as this rig is 25+ years old, my faith in these resistors is suspect. I want to construct a 'Chicken Stick' to slowly bleed tha capacitors to ground rather that just short them to ground using an insulated screwdriver which could 'blow' these caps.
    can anyone tell me what type/power etc resistor to put in series with the insulated grounded rod would do this.
    Thanks.
    Ron UK
     
  2. N3EF

    N3EF Ham Member QRZ Page

    I just use my multimeter. That way, I can monitor the voltage and see the discharge and know for sure they are discharged.

    Eric N3EF
     
  3. W2KG

    W2KG Subscriber QRZ Page

    "Chicken Stick"..neat name!

    Ron,
    I would think that the a resistor equal to the value of the bleeder resistors should do the trick. They are probably in the neighborhood of 500 kilohms at a 1/2 or 1 watt rating.
     
  4. G4ALA

    G4ALA Ham Member QRZ Page

    Charge Recovery

    Dear Ron,

    I read somewhere, though have never experienced, that a totally discharged electrolytic capacitor, if not shunted by a bleed or discharge resistor, can recover its charge and be capable of giving a shock.

    If you suspect the bleed resistors could be open circuit, it might be an idea, in addition to your original plan, to parallel or replace the bleed resistors, "just in case".

    73

    John

    G4ALA
     
  5. W8JI

    W8JI Ham Member QRZ Page

    Ron,

    The supply voltage is what, around 700 volts?? The tube current is a few hundred millamperes, perhaps 300 mA?

    700/.3 = 2100 ohms is what the supply runs into when operating, so that would be a very SAFE resistor to use in the chicken stick. I'd use a 2500-10000 ohm 10 watt resistor if it were my stick for that rig. The capacitors would discharge in a fraction of a second and the supply loading would never be any worse than the normal operating current so you would never blow up anything when discharging the caps.

    73 Tom
     
  6. GW1HIN

    GW1HIN Ham Member QRZ Page

    Hi Guys,
    Thanks for all the help. Will use a 10W 10k resistor. The reason for the concern is at the age of 77yrs, I guess I may be more susceptible to a rapid demise than you youngsters out there. lol
    73s
    Ron
     
  7. AG3Y

    AG3Y Guest

    Tom's advice is pretty good. In broadcasting, we used "chicken sticks" that were often called "Shepherd's crooks" because they were a fibreglass stick with a hook made of a piece of copper rod, tied to a piece of flexible cable which ended with an alligator clip on the other end. The clip was fastened to a ground point, and the hook was attached to the hot side of the capacitor bank.

    The advice about a capacitor "remembering" its charge sounds like an Urban legend, but it IS TRUE ! That is why the hook came in handy. It kept the stick in place while we worked on the power supply !

    73, and I hope you have many more years of hamming ahead of you !

    Jim
     
  8. WA9SVD

    WA9SVD Ham Member QRZ Page

    A "completely discharged" capacitor can't regenerate a charge. But a momentarily shorted capacitor may (probably!!) not be completely discharged, and over time, the electrochemical reaction inside can rebuild a significant charge. That's why after using the "chicken stick" to discharge the supply, it's a good idea to use a jumper to short out ALL HV or MV supplies while working on the equipment; just remember to remove the jumpers when finished.
     
    Last edited: May 17, 2008
  9. AG3Y

    AG3Y Guest

    I'll never forget when one of the guys forgot to remove the chicken stick from the caps when we had finished our normal maintenance for the night, and were ready to fire up the transmitter and make sure everything worked!

    He hit the HV button and WHOOOOOM ! The main circuit breaker for the transmitter tripped ! It sounded like a shotgun going off !

    We feared the worst, blown diodes, etc. etc. ! Fortunately the CB had done its job, and no permanent damage was done. ( except for some additional gray hairs on the CE's head ! ) :eek: :p
     
  10. KA0GKT

    KA0GKT Ham Member QRZ Page


    I remember a Hispanic engineer who called that device a "Palo-Jesus" or "Jesus Stick". It was his contention that if you didn't use the stick, you would see Jesus in short order. (band pun intended!)

    On my transmitters, the stick goes in before any part of my body goes in. I have a little chicken-stick which I use on my older tube-type gear. The stick has no resistor, it's only resistance is that of the copper wire connected to ground.

    There was an article in QST a year-or-so ago with a cute little Palo Jesus made with PVC pipe some hardware and a piece of insulated wire.
     
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