cz6a ?

[rbholt80]

Ok I was just wondering why the cz6a has a light bulb on the bottom board inside. It looks like a flash light bulb. Why couldn't fisher have used a resistor there and just what is the bulb doing. Has anyone else taken one apart and seen the bulb in there?

well the pic is bad but all i had was the phone to take a pic with. But it is a bulb with a filament in side it.

 

[kt315]

a bulb has high resistance in cold state and low being hottie. the bulb is kinda thermoresistance there. it stay in power supply wire +E on TX driver. when you turn on the detector a current speedy goes up. we must limit the current amlitude in the time.

yours

 

[rbholt80]

I get what your saying its sorta like a thermistor.

 

[kt315]

yes. you are right. my english is not so pretty good sorta the low-ohms thermistor with negative temperature resistance coefficient.

 

[rbholt80]

Could it be replaced with a thermistor? I ask cause I know that in radio and communication circuits small wire frays and long component leads can actually cause single drift and strange things. A light bulb would be horrible in tuned circuits. it acts like an antana and it has inductance and capacitive properties. But I guess Fisher knew what it was doing.

 

[tvr]

At 5 KHz and 15 KHz that filament isn't much of an antenna, not will it capacitively couple much. Calculate the wave length and you will see that it is a much better antenna at 6 GHz where some of the phone hand sets run.
Cheers!
tvr

 

[rbholt80]

Thats a good point. I wasn't thinking about the low khz of the detector I was just thinking about the ghz range and what the bulb would do. Well I aint concerned with the bulb really. What im doing with my old cz6a is modding it to have a toggle where the old pinpoint button was. This switch will be like an iron mask to open up my disc for a moment to check the iron falses. The pinpoint button was removed and i strait shafted the cz and put the pp as a trigger under the housing. I may build a new board to add to my disc control that is active and has selectable notches or just a notch for the high end of the conductive scale to eliminate the high falses. but thats just an idea yet

 

[tvr]

Some ambitious modification ideas. Keep us posted.

I have just about collected the parts I like for a straight shaft. Will do it for the CZ20 before the CZ6a that I have. But before that, will do some experiments to counter balance the coil weight on the Tejon.
tvr

 

[rbholt80]

here is a pic of the shaft mod and trigger i did a few years back.

 

[tvr]

Good looking weld on that handle to shaft joint. Shaft looks nice!

 

[rbholt80]

the control box can actually be moved forward or backwards as much as i want. Just need 7/16 wrench to loosen up a nut under the handle shaft thats attached all the way threw to the plate the control box is riveted to. It took some work to make that mod to the cz6a. what i had planned was to have 2 identical shafts but one would have an 8" coil the other would be the 10.5 then all i had to do was swap the control box when i needed the other coil. Its so easy to slide the controle box off the handle when i loosen the 7/16 nut. I dont really use the cz6a much anymore but I wont let it go cause i know it can get down and hunt deep.

 

[kt315]

Could it be replaced with a thermistor? I ask cause I know that in radio and communication circuits small wire frays and long component leads can actually cause single drift and strange things. A light bulb would be horrible in tuned circuits. it acts like an antana and it has inductance and capacitive properties. But I guess Fisher knew what it was doing.

certainly you can. but it will give nothing you on the sencitivity. every electronics component has own inductance and capacitive, but his role is very tiny. a light bulb is good simple decision, 'classic' in electronics. there is not need to change it on a thermistor.

trully yours