Adding swing

[Robb]

Thanks Robb.
Interesting video.
I haven't done the mod yet till I get to radio shack in a few days.
I am a little confused about clipping the limiter. Loosecannon said clip or remove the mod limiter but in the video it seems like he is saying ya shouldn't. I may be reading him wrong. Can ya clear it up
Thanks
God Bless

For the NPC mod to work, the limiter is clipped. So long as the rest of the modification is done as shown by loosecannon on this thread, it won't allow the the negative clipping/distortion to happen. As was shown in the video.

Instead, you can get up to 200% modulation before positive peak clipping/distortion occurs. Clipping out the limiter (removing R276) by itself isn't right. But with the addition of the NPC mod (adding the resistor, the diode, and relocating the C233 disc capacitor) it will keep it from negative clipping/distorting (look at the top of this page for all of the details).

The mic gain will control the amount of positive rise of peak modulation. If too much mic gain is applied; then you will get positive peak clipping. All you need to do is keep the positive peak from clipping by being careful with you mic gain adjustment.

EDIT:
Keep in mind that the output final transistor will be working overtime; as it will be driven harder. Put a heat sink on the back of the radio behind the driver and final transistor. Keep the peak wattage about 16 peak watts with a 2 watt dead key @ 200% modulation. At 1 watt dead key; you should see 8 peak watts @ 200% modulation - BTW.

 

[Oldtimer]

I understand !!!
Thanks again.

 

[Oldtimer]

Hi Cannon.
I understand everything ya said.With my big fingers instead of removing C233 cant I solder the IN4001 & 100ohm reststor combo on the solder side of the board. Unless I am reading wrong it is basically the same locations except flipped over. Am I correct??
Thanks
God Bless

 

[Oldtimer]

swing mod ????

Hi Loose Cannon.
I did the mod exactely like ya said and when I key the mic the needle pegs to the right. When I adjust vr14 or vr18 the needle dont move.
Also there is no modulation when I key the mic. The needle tries to swing backwards. I can hear myself when talkback is on.
Thanks
God Bless

 

[loosecannon]

first lets check the obvious things.

you do have your meter on the radio set to read power, and not in the SWR or CAL positions right?

if thats not it, you might have put the diode/resistor in backwards.

i noticed in your post that you were going to put them on the solder side of the PC board, which is fine, just make sure you have them soldered in the right place.
resistor should still be toward the back of the radio, and diode toward the front.

it really sounds to me like you have them soldered to the wrong traces.

also, if you dont want to clip the AMC resistor, you can just turn up the VR.
its not quite as "loud" as removing the resistor, but its pretty close.

dont key the radio anymore until you have confirmed that you have the diode/resistor combo soldered to the right traces, and also make sure that they are not shorting against any other traces or the case of the radio.
LC

 

[Oldtimer]

Hi all !!
I put everything back to stock and now I can set my dk by using the power knob.
I put the r276 back in and now after 30 seconds it smokes and still no mod.
I lost the original resistor. It call for a 10-ohm 1/8 watt. Thats what I put in.
I'm puzzeled.
Any suggestions ????
Thanks
God Bless

 

[Oldtimer]

Update !!!!
I removed the r276 and left it empty but my modulation is very low. I tried adjusting VR16 but no good.
Thanks

 

[Oldtimer]

Does anyone know what size resistor goes in R276 ?
The original one smokes and now I cant read it.
Thanks
God Bless

 

[Robb]

From what I can gather from your posts, I would recommend that you put the radio back to stock and maybe send it to a shop to do this mod and set it up with a scope to dial in the modulation.

Just saying . . .

 

[loosecannon]

oldtimer,

R276 is a 10 "K" ohm resistor, not a 10 ohm resistor.

that means 10,000 ohms.

you can use a 1/4 watt resistor if you cant find a 1/8 watt.

check your PM's, i replied to your message.
LC

 

[Oldtimer]

Thanks Cannon.
I put the right part in and It works again!!! Go figure !!!!!
It's all back to stock again and everything works great!!!!!!
Thanks again

 

[9C1Driver]

From what I can gather from your posts, I would recommend that you put the radio back to stock and maybe send it to a shop to do this mod and set it up with a scope to dial in the modulation.

Just saying . . .

AMEN. Good cb shops just love fixing d!cked up radio's.

 

[Holland]

Does anyone know how add more swing to a Galaxy DX 929.
Thanks
God Bless

Pod vr16 and vr15 on 16 make sure your switch is set to mod mic gain wide open