[ICOM] KEY CLIX --- 765 & 751A

[Ed Swynar]

Good Morning All, 

Well, my attempt to "cure" the key clicks from my 751A --- by copying a "...quick & dirty" mod that has proven to be effective with the 765 --- has met with failure...

For 765 owners wrestling with key clicks: replace "C108" (4.7 ufd. capacitor) with a 10 ufd. tantalum. I have it on good authority that this change should effectively "...smooth the edges" of the wave pattern enough to reduce clicks. Any more capacitance here, & the keying apparently becomes "mushy"...

There is no equivalent to "C108" in the 751A --- despite the similar-looking circuitry in this area --- so I simply added one...no change. I even put in a 1000 ufd. electrolytic here to study the effect --- its addition merely shaved the edges of the first transmitted character only. Once the capacitor was "charged", there was no effect whatever on the waveform...

Obviously I've managed to miss something here in the nuances between the 751A & the 765 circuitry for this particular stage...surely somebody, somewhere, must hold the key to the secret as to which specific components in the 751A might have a direct impact upon the waveform of the keyed signal coming out of it.

I shall certainly keep on looking...meanwhile, a happy, healthy, prosperous 2006 to all!

~73~ Eddy VE3CUI - VE3XZ