DX99 Over Modulated

[DarkEyes]

I received this radio a week or so ago. I got a SWR/MOD/PWR meter the other day and found out that this radio goes over 100% Mod if the mic gain is up over 1/4 of the way with the power all the way down (1.5W DK) What do I need to look for inside the radio to fix this. Is it a pot i can turn or has it most likely been clipped.
Thanks

[hilltop 439]

What kind of microphone are you using and what is the make of the meter.

[DarkEyes]

microphone is just a cheap cobra no power or noise canceling. The Meter is a TM-3000 marketed by AFDMS .

[hilltop 439]

The modulation pot on the Galaxy 99v is vr14 . The reason i asked what kind of meter you were using is because i use a TC3001P Dosy meter and the modulation meter in this thing has sucked from day one it like to tell fibs.

[DarkEyes]

Is there a easy way to tell if my meter is lying to me? It also looks like it was turned all the way up. Now as soon as the wife gets back with the car I can go test this out. Is there anything else I can easily look at while I am in here? I want clean audio out. I bought it from a truck driver and have no idea what mods he might have had done to it but I know he runs a lot of power. Thanks

[Night Crawler]

this radio goes over 100% Mod if the mic gain is up over 1/4 of the way with the power all the way down (1.5W DK)

Check the modulation with the radio on high power.
When the modulation is adjusted during alignment it's done with the radio on high power.

[hilltop 439]

Check to see if tr53 is missing or one side is clipped i think that is the modulation limiter and also take a look at r-238 and r-249 to see if they to have been removed.

[DarkEyes]

It looks like R238 has been messed with. [Please login or register to view this link]
Have not found R249 yet. And will be checking mod at full power here in a min. Got to wait for the wife to get back with my mic, I left it in the car.

[Night Crawler]

Oh My God that's brutal what did that guy use a propane torch to solder with.

What was done is referred to as the "Super Swing Mod" that diode shouldn't be there in a stock radio and R238 was replaced with a different value.

Remove the diode and replace the burnt resistor which is R238 with a 5.6k one end of the resistor soldered in the hole where the diode was removed from and the other end where where the burnt resistor was remove from.

Align the high and low power pots for the correct output.
With the power set to high adjust VR13 for 8-10 watts output.
With the power set to low adjust VR16 for 1-3 watts output
Adjust VR14 for 100% modulation

Make sure you keep the picture you posted as a keepsake

[DarkEyes]

I am also running a small 2X2SC2290 amp, do i need the "Super Swing Mod" to drive the amp... Keep in mind all I care about is a clean output. And I am willing to put some time into making it as clean as it can be. Thanks for the help everyone.
PS 5.6K is Green Blue Red Gold???? I think

[Night Crawler]

Green Blue Red that's correct you don't need the swing mod to drive the amp just adjust the low power to whatever power level you need to drive it.

[DarkEyes]

Green Blue Red that's correct you don't need the swing mod to drive the amp just adjust the low power to whatever power level you need to drive it.

Do I need to adjust for 100% mod at full power or at low power?

[DarkEyes]

Well here is the back side of R238, I am not shure if this is how it should be connected or if this is part of the mod. I have not done anything to it yet. I will wait for a reply.

[DarkEyes]

oops image here [Please login or register to view this link]

[hilltop 439]

Holly O SH@#T !!!!!!! what a mess . If it your me i would restore the radio back to it's original state taking the mod completely out of the radio. I have not personally performed this mod before so i am not sure what the wire is for. Check out [Please login or register to view this link] and get the parts layout and see what belongs in place of the bad parts . You may have to clean up those traces and repair them it's not that hard just look at the schematic and trace layout take your time and you will have it talking in no time .

[Night Crawler]

First thing to do is get some solder flux remover ,contact cleaner or alcohol and clean that crude off I"ll look at the PCB layout and let you know what has to be done.

Holly O SH@#T !!!!!!! what a mess .

And that ain't no joke a one eyed monkey could do a better job!

[Night Crawler]

I have not personally performed this mod before so i am not sure what the wire is for.

That wire goes to the power adjustment control on the front of the radio it's not part of the modification.

[DarkEyes]

Ok this will give me something to do for a little.. Thanks for all the help.

[DarkEyes]

Alright repair is complete. Got a question about one of the traces is lifting off the board? Do I just leave it hanging there or should i try and glue it back down?
[Please login or register to view this link]
Got it set to 2 watt min power, 8 watt max, with 100% modulation on full power.
Something else weird seems to happen and I don't know if its the radio or my meter. When set at min power 2 watts it swings to 12 or so but then will stay up around 5 or 6 watts with no modulation but mic key still held down. Now if I let go of the key and re key the mic its back to 2 watts. This might be normal i don't know, never had a power meter to play with before.

[Night Crawler]

That looks alot better one thing you could do is to apply some solder to that trace with the hole on the right where the wire bends over to the trace next to it. If that's the trace that's lifting up you really don't have to glue it down after you solder it the wire going through the hole will hold it in place.
As the meter are you taking the readings in the PEP (peak envelope power) position?

I have a question what was holding the diode and resistor together was that solder or aluminum foil I've never seen anything quite like it.

[DarkEyes]

Ok I will add a dab of solder there. And yes I am using the PEP on the meter.

[Night Crawler]

That's probably the reason it's doing that use the average power reading and see what happens.

[DarkEyes]

Using AVG i get 2 swing to ~4 on low and 8 swing to ~12 on high.
Also I know cbtricks has all the schematic and stuff, but there is one more jumper wire attached to the solder side.
Looks like it goes to VR5 or something around that area, any ideals what it might be?

[Night Crawler]

If you can post a picture I'll see if I can trace it down VR5 is the deviation adjustment pot (audio level adjustment when transmitting) for FM.
Don't tell me he tried to a swing mod to that too it's not going to work.

[DarkEyes]

[Please login or register to view this link]
It might be stock I really don't know, it just looks like it was added by someone with some not so great soldering skills.
Thanks