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Junior Member
Username: Bbmfic

Post Number: 32
Registered: 1-2003
Posted on Saturday, November 27, 2004 - 2:53 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

i have a older 2990 that needs the npc rc mod done to it can some one tell me what it is thanks alot bbmfic
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Intermediate Member
Username: Inspector

Post Number: 110
Registered: 12-2001
Posted on Wednesday, December 01, 2004 - 1:34 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

One thing to keep in mind, is that if you intend to do any mods to the output (swing, power, etc), you should look into beefing-up the power-supply. These power supplies have had a history of failure...for many reasons. Having said that, the best way to do the NPC mod is to first have your radio tuned propperly, with the modulation set at no more than 100% (no clipped limmiters!) once that is done, dial the RF power all the way down. I remove the built-in amp from the circuit by unplugging the key-up wires from the main board (two-wire plug, brown and black, just in front of the driver transistor). Now, make note of the wattage on low and high without the amp. Solder one end of a 100 ohm resistor to one end of a 1N4001 diode and bend into a "hairpin" shape. Add the diode-resistor combination to the bottom of the main board- to the two solder points of ceramic disk capacitor C300 (or resistor R285...they share the same solder points)...install with the banded (cathode) end of the diode to the solder point, of C300, nearest the rear of the radio. Now key-up radio and make sure the low deadkey without the amp is like it was before...if not, adjust the low power pot VR15, to get it back. Modulate and notice the swing. The carrier to swing ratio should be 4:1 (like 1W swing to about 4W). Plug the amp-key-up wires back and check the output NOW! Adjust your variable power to maintain that ratio at the higher output and your signal should run clean with no problems.

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