I have almost finished by testing of the Phase Lock Circuit K21. I had lots of problems with this circuit some due to lack of component values mainly on the capacitor which I have resolve. Found posts with correct values in this forum I have a link to that in the report I am writing. Thing I still having issues with is the (A) signal input. I can get it into the circuit but can not get the pulse past the first stage 4001. At first I though it was because signal was not going completely low and that the Zener diode would fix this issue. It did drop the signal offset to zero but did not solve the issue. I got side tracked working on other parts of circuit and testing other functions. I had check if signal input is high output of 4001 goes low and stops signal. Normal state was High which is what you want for VCO to work so I went on to test and checking other things which took quite a while. Never finished checking impact of the (A) gate.
When I tried to do that I found I still could not get the (A) signal to switch the 4001 from high to low. Turns out signal from K3 is not large enough to cause the 4001 to switch. My testing shows it needs to be around 7 volts to get it to pass the gate pulse. But its only about 4.6 volts and only when I switch the 2.2K resister show on the diagram from ground to +12V. I did get it to work with a 39 ohm resistor but that really got hot burned the marking on resistor. Also did not like the fact that the Zener diode was letting higher voltage back to K3.
I tried dropping VDD in to 4001 to 10 volts to see what would happen - first it did not let the (A) pulse through and it also dropped output signal level (G) to 11 volts from 12 volts as the signal output level is determined by VCC.
Kind of odd that there is that much of a mismatch on signal levels. May have the output on K3 wrong not sure but that is a 5 volt board. I know those chips do not like 12 volts it burns them out did that! Need to solve this problem it is now last test in my testing but not sure what to do as I do not like using that small of resistor as a pull up as it pulls to much current and voltage levels are already a big issue with K21 circuit.
I do have most of the analysis and test report done just need to figure out how to test this problem before I publish it.
When I tried to do that I found I still could not get the (A) signal to switch the 4001 from high to low. Turns out signal from K3 is not large enough to cause the 4001 to switch. My testing shows it needs to be around 7 volts to get it to pass the gate pulse. But its only about 4.6 volts and only when I switch the 2.2K resister show on the diagram from ground to +12V. I did get it to work with a 39 ohm resistor but that really got hot burned the marking on resistor. Also did not like the fact that the Zener diode was letting higher voltage back to K3.
I tried dropping VDD in to 4001 to 10 volts to see what would happen - first it did not let the (A) pulse through and it also dropped output signal level (G) to 11 volts from 12 volts as the signal output level is determined by VCC.
Kind of odd that there is that much of a mismatch on signal levels. May have the output on K3 wrong not sure but that is a 5 volt board. I know those chips do not like 12 volts it burns them out did that! Need to solve this problem it is now last test in my testing but not sure what to do as I do not like using that small of resistor as a pull up as it pulls to much current and voltage levels are already a big issue with K21 circuit.
I do have most of the analysis and test report done just need to figure out how to test this problem before I publish it.