Where is the AMC limiter on Galaxy 929?

[gunner57]

I have a galaxy 929 and I want to see if the modulation limiter is clipped or not. Can someone give me a location for it? I opened up the radio and nothing looks like it was cut, but I could be missing it. It is possible it was removed and I wouldn't see anything clipped. Any help would be great. I am trying to re adjust the radio back to decent levels. It dead keys 12W and peaks at 20. The mic gain has to be set at 1/4 for 100% modulation with an Astatic 636L.

[MDYoungblood]

Here are the adjustments for the Galaxy DX929:
VR9-TX Meter, VR18-Lo PWR, VR14-Hi PWR, VR16-AMC, VR15-Mod Meter, VR1-AM S Meter, L1-Noise Blanker, L20-AM Freq, VR4-Sq Range
TX Tune-up: L44, L43, L42, L40
RX Tune-up: L5, L6, L7, L8, L9, L10, L2, L3

3's

Greg

[Z-MAN]

I will check for you on the limiter location, but does a 929 share the same board as a 959? Anywhoo, i will look.

[MDYoungblood]

No they don't share the same PCB, just the adjustment pots are marked with the same id's. Must be the way the engineer designed (drew) the boards.

3's

Greg

[gunner57]

Here are the adjustments for the Galaxy DX929:
VR9-TX Meter, VR18-Lo PWR, VR14-Hi PWR, VR16-AMC, VR15-Mod Meter, VR1-AM S Meter, L1-Noise Blanker, L20-AM Freq, VR4-Sq Range
TX Tune-up: L44, L43, L42, L40
RX Tune-up: L5, L6, L7, L8, L9, L10, L2, L3

3's

Greg

Thanks. I was checking out the transmitter alignment locations on cbtricks. But I can't seem to find the location of the modulation limiter.

I hooked up my meter to try to get my radio a little closer to normalcy, but it ain't happening by me. It is beyond my capability. I noticed one coil in the back center of the chassis was spread apart in two places and another coil in the back and toward the right (right as viewed from the rear) had a 1vsmall spread. The radio was dead keying `12W and swinging up to 20W on high power. On low power it dead keyed 8W and swinging 20W. My modulation % was pegging the meter pretty hard, even with an Astatic 636L, I had to turn the mic gain down to 1/4 to get it where it should be. I adjusted the V16 and had to turn it down to the stop to get my modulation to peak at 120% with the mic gain maxed. That is better than it was. My output dropped to 14W PEP, which is ok but I'd have liked to see it stay up around 20W. I also adjusted VR18 and VR14. My dead key is now 3W on low power and 8W on high power. My radio is still peaking about 15W. I am keeping my variable power so I am dead keying a little over 4W for a 1:4 ratio. I don't know what else has been done to the radio. Spec shows that low power should dead key down to .3W, not that I want it that low. But I literally can't get it below 3W by adjusting VR18.

I bought this radio new with a "peak and tune." It was my first new purchase and at the time that peak and tune sounded pretty awesome. That was before I knew anything about radios. This tune was just someone turning up the pots to max. I am glad it wasn't used hard or it may have burned out by now. I am going to send it out to get re-aligned by someone who knows what they are doing. I'd still like to know if the limiter was cut or not, if anyone can show me where it is. Just for my own reference.

[rayray1963]

If memory serves me, the limiter is at R249.


Sent from my iPhone using Tapatalk

[Z-MAN]

Lower the high to 5 or 6, then your low can get to 1w, then turn the AM power back up after you replace the limiter. Good job RayRay!!

[MDYoungblood]

The limiter is R276, it is located just right of VR16. If it has some other things may have been done, here is a power mod for that radio I found on another forum;

First, cut or remove R276. its just to the left of VR16. this is the AM modulation limiter.

next, find C233 and remove it. don't 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 doesn't matter what direction you solder it)

now, as for the dead key not going any lower than 3 watts, you have to understand that there are two VR's that control your dead key 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 doesn't 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 dead key 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 dead key of 4 watts.

now turn the RF power knob all the way down again, and check your dead key.
if its not still at 1 watt, adjust VR18 for 1 watt.

turn the RF power knob all the way up and check your dead key. 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 dead key from 1 to 4 watts, and the radio will swing up to its maximum PEP potential no matter where you set the dead key.
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3's

Greg

[gunner57]

Lower the high to 5 or 6, then your low can get to 1w, then turn the AM power back up after you replace the limiter. Good job RayRay!!

The high won't lower any more.

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Thursday, 01 August 2013, 22:09 PM

Thanks MDyoungblood. I will check to see if the limiter is gone.

As far as the rest: VR18, VR16, and VR14 are all turned all the way down and the radio dead keys 8W on high power, and 3-4W on low. Modulation % is just over 100% with the mic gain maxed out, on the radios internal mod meter and my Dosy mod meter.