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Discussion in 'CB and Export Equipment and Accessories' started by Oldtimer, Aug 12, 2011.
If this is true; then unsolder just the one end of R266 that connects to D103 and C233. Then solder the 'banded' end of a 1N4001 diode into the empty hole where that resistor's end was unsoldered - and then solder the other end of that 1N4001 diode to the end of that same lifted R266 resistor end that you pulled up off the board.
But this info MUST be VETTED - FIRST.
Maybe loosecannon or another radio guru can verify or correct this info as correct first. Oldtimer, I would stay tuned and come back to this thread to see if/when this correction/verification comes through. Don't act on the info I gave until/unless it is a sure thing!!!
This should lower your dead key watts, as this is the NPC/RC mod. Only if that info is correct. But if it doesn't lower it to where you need after you turn your RF Power Output knob all of the way down; then VR18 is the one you want to adjust to get 1 watt dead key. Make certain that your mic gain is turned all of the way down first when adjusting VR18.
Robb I tried this but it wont lower anymore than 3 watts ???????????????
First of all, don't do ANY mod until someone can verify that my mod is correct for that radio in particular. Loosecannon or a few others can do that when they read this post.
The 1N4001 is the one to use; the 1N4004 isn't the right part. The 1N4001 cost about $.05/$.25 or so; even Radio Shack carries them if I'm not mistaken.
1N4004 will work! Its just rated for higher voltage than the 1N4001, and its bigger.
You right on the mod Robb! The diode goes series with R266 and the band faces the back of the radio, R-186 is the mod resistor for AM only, you can cut or lift it. Just turning up VR-16 might not give you the mod you want.
I never had a non SSB Galaxy but you should be able to volt the final to prevent over heating of Q54
Here is a good site for 949/959's your 929 is really close minus the SSB.
The Defpom EPT06960Z Galaxy 949 / 959 modifications
A single final radio should have a low dead key @ 1 watt when the RF Power Output knob is turned all of the way down. When the RF Output knob is turned all of the way up, it should be no more than 4 watts dead key/no modulation.
A dual final radio has a low dead key of 2 watts, and a high dead key of 8 watts.
Do you have a MOSFET or bipolar transistor final? The MOSFET may have a higher dead key wattage when turned all of the way up; but it still should come down low when the RF Output is turned all of the way down.
Joe D; have you done this mod on the 929 before?
No offense meant nor implied; just curious is all.
I know that loosecannon would know if it is right.
i have a 929, and have done the mods to it that im about to suggest, so i know they work.
refer to this diagram for the parts locations:
click on the diagram to enlarge it.
first, cut or remove R276. its just to the left of VR16. this is the AM modulation limiter.
next, find C233 and remove it. dont cut it. unsolder and remove it as you will be re-using it. C233 is located in the rear right corner of the board, just to the left of Q55.
get a 100 ohm resistor (1/4 watt is fine), and a 1N4001 diode. (yes, your 1N4004 diode will work fine, but the leads may be to large to fit through the hole in the PC board)
solder one end of the 100ohm resistor to the BANDED end of the diode.
refer to the diagram at the bottom of this post to see how it should be done.
put the diode/resistor combo in the holes where C233 used to be, and solder it in.
the resistor should be towards the back of the radio and the diode towards the front.
now, on the solder (green) side of the PC board, solder the capacitor you removed to the two spots where you just soldered the diode/resistor.
(basically you are putting it back where it was, just on the other side of the PC board. its not polarized so it doesnt matter what direction you solder it)
now, as for the deadkey not going any lower than 3 watts, you have to understand that there are two VR's that control your deadkey level, and they work together.
here's how it works:
because you have a variable RF power control on the front of the radio, there are two internal controls that allow you to set the thresholds or limits of your high and low power. (max clockwise and max counterclockwise on the RF power knob)
these two VR's are VR18 (low power limit) and VR14 (high power limit)
they do interact with one-another and turning one will affect the level of the other so it does take just a bit of going back and forth to get them set where you want.
here's now to do it:
turn the mic gain all the way down so it doesnt affect your readings.
now, turn the RF power knob on the front of the radio all the way down. (counterclockwise)
adjust VR18 until you get a deadkey of 1 watt.
if it wont go down that far, turn VR14 to lower the high power limit enough to allow you to set the low limit at 1 watt.
once you get that done, turn the RF power knob on the front of the radio all the way up. (clockwise)
now adjust VR14 for a deadkey of 4 watts.
now turn the RF power knob all the way down again, and check your deadkey.
if its not still at 1 watt, adjust VR18 for 1 watt.
turn the RF power knob all the way up and check your deadkey. if its not still at 4 watts, adjust VR14 until it is at 4 watts.
that should do it, but you may have to bounce back and forth a few times to get it right.
the important part is to have the RF power knob turned all the way down when adjusting VR18 and all the way up when adjusting VR14.
now you should be able to vary your deadkey from 1 to 4 watts, and the radio will swing up to its maximum PEP potential no matter where you set the deadkey.
Now there ya go OldTimer.
Done like a pro!
You should be able to get some real powerful peaks out of that radio. The thing is, keep the power down to where you need it. If you have a power meter, make sure you don't push the radio past 18-20 watts peak power. Keep it running cool, and it will keep running. Set your mic gain after you set your dead key @ 1 watt.
Pushing the mic gain too high will only make you sound worse IF you can't get a radio check from a local friend that can help you get it dialed in. That is a pretty important step to make this mod work for you. You will have TONS of modulation; just don't adjust it so high that you have a ton and a half. A lot is great; too much is baaaad . . .
Can I use a power mic (Turner+3 ) as long as it is turned down with this mod???????????
I think that would be the mic I would choose. They have a built-in audio compressor circuit in these mics which would make you sound even better - IMO.
The biggest problem I see is turning the mic gain up too high and making it all sound nasty. Get a radio check from someone you know and trust, start out with the mic gain low and work your way up until it just starts to distort. Then back it off slightly. The mic modulation should be adjusted with a scope by a tech; but if you are careful with the mic gain, you should be fairly close.
Watch this video to see what the NPC mod gas done for your modulation. They call it a 'Mauldulator'; but the O-scope shows what the NPC mod - or this 'swing mod' you have done - looks like. That is what your radio is doing now on a scope OldTimer:
Mauldulator on the Galaxy 2527.wmv - YouTube
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