I went to adjust the V4 pot on my Cobra 29 LTD Classic, and when i turned it the plastic screw broke off. The radio transmits fine, and was curious if it will hinder performance later on?
Let's see you wanted more modulation, so you twisted the VR4 pot so hard that it broke off . First, if the radio has been clipped, VR4 is not in use . FYI, I think that full Counter Clockwise is wide open . VR4 is a 680 ohm pot, but can read to 800 ohm . Most folks defeat the AMC circuit by removing D11, C73 will do the same . You may actually be better off by leaving the circuit intact, and changing C71 from a 220uf 10v to a 33uf - 47uf at 16v, or 25v, to 50v . This will make the AMC transistor react faster for cleaner operation . Set VR4 so that it just prevents severe over-modulation . If you want modulation that bad, change C42 to a 3300uf 16v - 25v . That will increase available power for your audio amp . Make sure that R48 is 220K Ohm . For swing, remove Jumper JP36, and install a 18 ohm to 100 ohm 1 watt resistor(higher number = lower dead key) in parallel with a 47uf to 100uf 50v cap . I use axial caps, if you can find them, and piggyback the resistor . Outherwise, it can be mounted on the botton of the board . Make certain that the negative lead of the cap is in the rear hole . Without an amp, I use 18 ohm, and 47uf at 50v . I also add a "short" jumper on the bottom of the board from the audio transformer base ground to the center grounded area of the board to prevent feed back . You just have to jump a few small traces . The center area is grounded, follow skinny the traces . The jumper just beefs up the ground . Well, I hope that satisfies your lust for modulation ! J
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