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Cobra Radios |
Model |
Power Tips |
Mods |
Page 2 |
Variable Power for Cobra 25 & 29LTD Cobra 25 LTD Find and remove C70 & JP6(near Final). Disconnect Orange and Brown wires from the RF Gain Control,then connect these wires together. Install Q1 where JP6 was.The right leg(emitter) of Q1 in the hole near the final.The Centre leg(collector) in the other hole. Solder a wire from the left leg(base) of Q1 to the centre tag of the RF Gain Control. Remove VR5(near transformer) Connect the last tag of the RF Gain Control to a 100ohm resistor and solder to L6 pot. Solder a wire from the upper tag of the RF Gain Control to the top connection of VR5(already removed) Cut D9 out of the circuit (this is the Clipping Diode) Put plenty of heat sink compound onto the tab of Q1, then using the proper mounting hardware mount to heat sink (make sure that the tab of Q1 is insulated from the heat sink) Cobra 29LTD Follow instructions for Cobra 25LTD, except remove C73 & JP36 instead of C70 & JP6,remove VR4 instead of VR5, Also cut D11 instead of D9. Q1 = TIP120 (Radio Shack), capacitor = 22 uF 25 V |