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FT 101ZD VFO Issue

A. John Hecht All Messages By This Member #495 I recently was given two FT101ZD's, one a "Parts rig" Mark I and the other a Mark II. ?Both required work but both are now working. ?I found I had to remove the voltage to PIN 2 of the VFO input connector to calm down the VFO in the Mark I. The VFO was moving like crazy and when it did settle down it still had an issue with warble. ?Removing the voltage solved the issue but now of course the Clarifier function is no longer. ?It appears that the variable-cap diode (D01) for the clarifier circuit is defective. ?I have some of those diodes on order from China so I'll know soon enough after they arrive. ?Has anyone else had an issue with this vari-cap diode??
Emerson PP6EW All Messages By This Member #496 John I guess you can replace the varicap by a 1N4001 -1n4007. Emerson PP6EW Em sáb., 22 de jun. de 2024 às 20:34, A. John Hecht via <k6koi=[email protected]> escreveu: toggle quoted message Show quoted text I recently was given two FT101ZD's, one a "Parts rig" Mark I and the other a Mark II.? Both required work but both are now working.? I found I had to remove the voltage to PIN 2 of the VFO input connector to calm down the VFO in the Mark I. The VFO was moving like crazy and when it did settle down it still had an issue with warble.? Removing the voltage solved the issue but now of course the Clarifier function is no longer.? It appears that the variable-cap diode (D01) for the clarifier circuit is defective.? I have some of those diodes on order from China so I'll know soon enough after they arrive.? Has anyone else had an issue with this vari-cap diode??
Jim Shorney All Messages By This Member #497 I recently repaired a FT-707 that had, among other things, clarifier issues. I found that the JFET constant current source and the Zener diode in the clarifier power circuit to be bad. Not flakey, hard failures. The clarifier voltage source must be absolutely stable. More stable that what you can see on the average DMM. After all that the clarifier frequency was lagging behind the action of the knob. It sounded like a capacitive charge curve. I checked EVERYTHING in and around the VFO and clarifier. Including the varactor. It was driving me nuts. It turned out to be the stupid connector that plugs into the VFO. Check the simple stuff first. 73 -Jim (I hope I never see that radio again) NU0C On Sat, 22 Jun 2024 15:10:00 -0700 "A. John Hecht via groups.io" <k6koi@...> wrote: I recently was given two FT101ZD's, one a "Parts rig" Mark I and the other a Mark II. ?Both required work but both are now working. ?I found I had to remove the voltage to PIN 2 of the VFO input connector to calm down the VFO in the Mark I. The VFO was moving like crazy and when it did settle down it still had an issue with warble. ?Removing the voltage solved the issue but now of course the Clarifier function is no longer. ?It appears that the variable-cap diode (D01) for the clarifier circuit is defective. ?I have some of those diodes on order from China so I'll know soon enough after they arrive. ?Has anyone else had an issue with this vari-cap diode?
A. John Hecht All Messages By This Member #498 Thank you Jim for taking the time to respond to my posting. I agree that a DMM would not detect a very slight voltage variation in the DC, especially if the sampling rate of the DMM is too slow. And even with a scope it would be a challenge to see ripple without very careful adjustment of triggering, etc. So to check the voltage I substituted battery. The warble returned with that voltage. I really think it’s the var-cap diode. We’ll see. I might just leave the voltage off pin 2 of the 4 pin to the VFO and claim success! (Not an elegant solution.) BTW, I also agree that connectors are always suspect in these old rigs. In fact some of the Molex connectors were I did use De-Oxit on the connectors to and from the VFO. toggle quoted message Show quoted text On Jun 22, 2024, at 8:35?PM, Jim Shorney via groups.io <jimNU0C@...> wrote: I recently repaired a FT-707 that had, among other things, clarifier issues. I found that the JFET constant current source and the Zener diode in the clarifier power circuit to be bad. Not flakey, hard failures. The clarifier voltage source must be absolutely stable. More stable that what you can see on the average DMM. After all that the clarifier frequency was lagging behind the action of the knob. It sounded like a capacitive charge curve. I checked EVERYTHING in and around the VFO and clarifier. Including the varactor. It was driving me nuts. It turned out to be the stupid connector that plugs into the VFO. Check the simple stuff first. 73 -Jim (I hope I never see that radio again) NU0C On Sat, 22 Jun 2024 15:10:00 -0700 "A. John Hecht via groups.io" <k6koi@...> wrote: I recently was given two FT101ZD's, one a "Parts rig" Mark I and the other a Mark II. Both required work but both are now working. I found I had to remove the voltage to PIN 2 of the VFO input connector to calm down the VFO in the Mark I. The VFO was moving like crazy and when it did settle down it still had an issue with warble. Removing the voltage solved the issue but now of course the Clarifier function is no longer. It appears that the variable-cap diode (D01) for the clarifier circuit is defective. I have some of those diodes on order from China so I'll know soon enough after they arrive. Has anyone else had an issue with this vari-cap diode?
A. John Hecht All Messages By This Member #499 开云体育 Emerson, do those diodes function as vari-caps? ? toggle quoted message Show quoted text On Jun 22, 2024, at 7:18?PM, Emerson PP6EW via groups.io <bunhoel@...> wrote: John I guess you can replace the varicap by a 1N4001 -1n4007. Emerson PP6EW Em sáb., 22 de jun. de 2024 às 20:34, A. John Hecht via <k6koi=[email protected]> escreveu: I recently was given two FT101ZD's, one a "Parts rig" Mark I and the other a Mark II.? Both required work but both are now working.? I found I had to remove the voltage to PIN 2 of the VFO input connector to calm down the VFO in the Mark I. The VFO was moving like crazy and when it did settle down it still had an issue with warble.? Removing the voltage solved the issue but now of course the Clarifier function is no longer.? It appears that the variable-cap diode (D01) for the clarifier circuit is defective.? I have some of those diodes on order from China so I'll know soon enough after they arrive.? Has anyone else had an issue with this vari-cap diode??
Jim Shorney All Messages By This Member #500 I think pretty much any diode can be used as a varactor. Some are just better than others. 73 -Jim NU0C On Sun, 23 Jun 2024 07:45:50 -0700 "A. John Hecht via groups.io" <k6koi@...> wrote: Emerson, do those diodes function as vari-caps? On Jun 22, 2024, at 7:18?PM, Emerson PP6EW via groups.io <bunhoel@...> wrote: John I guess you can replace the varicap by a 1N4001 -1n4007. Emerson PP6EW

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