NPC-RC Modification for 6900xxx Type Boards
OK guys and gals a little studying needs to be done here but if you havent noticed the 6900xxx board found in say the galaxy 94hp and the 069610Z board of the Galaxy 949/959 are basically the same even part numbers are the same,, so I will do only one to save time……
Parts needed 1- 1n4001 diode
2- 100ohm resistor
3- 6 inch piece of 18guage stranded wire
Step 1- Take the diode and resistor and solder the banded end of the diode to the resistor…Then fold the other end of the resistor down to form kinda like a hair pin….(see attachment 1)
Step 2- C233 needs to be removed from the board and saved for use in another step (see attachment 2)
Step 3- Now take diode resistor combo and place where C233 was with diode lead in the hole facing the front of the radio and the resistor lead in the hole facing the rear of the radio.. Now solder diode resistor combo in place then take the capacitor you took out of C233 and solder to the diode resistor combo on the solder side of the board .. Make sure the cap if as flat as possible so it doesn’t interfere with the top case lid..
Step 3- Look near the final you will see a Bias board on SSB radios and a set of jumpers on AM/FM only radios, this is where TP7,8,and 9 are,, on this board TP8 needs to be removed,, on SSB radios there is a clip for TP8, remove the clip then replace the bias board…. ON AM/FM only radios you need to remove the jumpers from TP8 and lift out of the hole and then solder together so now the jumper goes from TP7 to TP9 bypassing TP8.…(see attachment 3)
Step 4- Take your piece of 18 gauge wire and strip 1/8” off each end and tin with solder,, now where you removed the clip or jumpers from TP8 solder one end of the wire to this point on the solder side of the board,, now solder the other end to the 12v rail of the emitter of Q54 (see attachment 4)
Step 5- R276 needs to be disabled this is the AMC for this radio and by disabling this resistor on SSB radios the SSB should not be affected,,, now you need to find Q57 and 39, if they are there and unmolested leave them alone and if they are missing replace them,, these are components of the AMC also but will affect SSB….(see attachment 5)
Step 6- The power needs to be retuned now.. The high power needs to be set first.. Put variable knob on the high setting now inside the radio look for VR14 set this for 7 watts on low power radios and for high power radios set for 25 watts.
Step 7- Put the power variable to the lowest setting,,, now adjust VR18 for 2 watts for low power radios and 5 watts if you desire for high power radios,, go back and check high power settings to make sure they are correct, if not, tune accordingly….
Step 8- For the driver check bias as per the Galaxy 98VHP service manual on the main CBT website…… Now for the final since the clip for TP8 is gone you cant check final bias as per the service manual so what you need to do is disconnect the red wire and place the meter leads in series with the wire and the spot where TP8 clip use to be…. (thanks to Rickey aka couch potatoe for the correct procedure on this step)
I would highly recommend using non conductive tuning sticks for steps 6 thru 8.…..
This is for educational purposes only,, I am not responsible if you burn your radio or mess it up in any way……
Thanks to Billy Dean Ward aka CB Doctor for all the help and knowledge for this modification……
This is my post from Billy's old forum RF Study Group,, I know this post is a few months old but i hope it helps
Dean