Post by Skoal Spitter on Nov 21, 2006 2:18:10 GMT -5
Cobra 29 LTD:
Receive Boost: Locate pin 14 of the PLL chip, and the Positive (+) side of C-12. Install a 22k-220k ohm resistor between these two points. The smaller the value, the more the receive is boosted. Use CARE when soldering to the PLL chip! If desired, this mod may be wired through a switch.
Supertune (GALAXY FINAL): Replace the stock final with a 2SC1969 unit. Solder a jumper across D8 (this may cause receive distortion at high volumes, remove jumper if it does). Solder a 68pf cap across C62. Solder a 68pf cap across C59 if there is already a 33pf across it. If there isn't, use 100pf instead. Replace R 55 with a 10-15k resistor, and solder a 33-55 pf cap across that resistor. Replace R58 with a 4.7 ohm resistor. Set VR4 just a bit to the right of half-way open. If D11 or C3 have been removed, replace them. D11 is a simple small-signal swithcing diode like a 1n147, and C3 is just a 1uf electrolytic. If TR18 has been removed or cut, replace with a 2SA733. Spread Open L12 a tiny bit, and adjust L16 for best swing, using a loud, steady "aaaaaaah" sound into the mic (or if you have a function generator, set it up for 1khz at about 16mv output, and use that. MAKE SURE to use heat-sink compound (a very light coating is sufficient) when mounting the new final, and MAKE SURE the final mount screw is tight!
Channel 9 switch to Channel 19: Cut D32. Hard, huh?
This is not my original work. Full credit goes to Dave at dtbradio.
Receive Boost: Locate pin 14 of the PLL chip, and the Positive (+) side of C-12. Install a 22k-220k ohm resistor between these two points. The smaller the value, the more the receive is boosted. Use CARE when soldering to the PLL chip! If desired, this mod may be wired through a switch.
Supertune (GALAXY FINAL): Replace the stock final with a 2SC1969 unit. Solder a jumper across D8 (this may cause receive distortion at high volumes, remove jumper if it does). Solder a 68pf cap across C62. Solder a 68pf cap across C59 if there is already a 33pf across it. If there isn't, use 100pf instead. Replace R 55 with a 10-15k resistor, and solder a 33-55 pf cap across that resistor. Replace R58 with a 4.7 ohm resistor. Set VR4 just a bit to the right of half-way open. If D11 or C3 have been removed, replace them. D11 is a simple small-signal swithcing diode like a 1n147, and C3 is just a 1uf electrolytic. If TR18 has been removed or cut, replace with a 2SA733. Spread Open L12 a tiny bit, and adjust L16 for best swing, using a loud, steady "aaaaaaah" sound into the mic (or if you have a function generator, set it up for 1khz at about 16mv output, and use that. MAKE SURE to use heat-sink compound (a very light coating is sufficient) when mounting the new final, and MAKE SURE the final mount screw is tight!
Channel 9 switch to Channel 19: Cut D32. Hard, huh?
This is not my original work. Full credit goes to Dave at dtbradio.
