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Galaxy 949 PLL alignment problem

N

n3umw

Member
Jun 24, 2010
9
3
13
I have two radios (DX2547 AND DX949) with the exact same problems
1) VR7 (transmit offset) is not adjustable to spec
2) AM is OK, but SSB is unintelligible.

--------------

On July 5th, 2010 I ordered a DX2547 radio as a match for my 5 year old DX949 mobile.

A week after receiving the radio I noticed the SSB receive frequency had drifted. I left the radio turned on 24/7 to see if there would be additional drift.

After a week of burn-in, it had drifted so far that the clarifier had to be turned completely CCW to be at the center receive frequency. Not sure what the transmit frequency was doing as there is currently little SSB activity in my area. Listening on my HF rig, SSB audio sounds funny but hard to tell. After several weeks radio seems to have stabilized.

I have the factory and Lou Franklin service manuals so I decided to open it up and realign the PLL circuit.

Warmed it up and removed TP7/8/9 PCB.

The voltage at TP2 was quite a bit below 2.5VDC, but L14 readjusted OK.

No scope available for the L15 adjustment.

Adjusted VC1, L20/21/22 to RX spec. using external frequency counter at test points. Internal frequency counter is now centered.

Unable to readjust VR7 to 16.267500 MHz. Reads above frequency (from 16.2693-16.2721) and pot is completely CCW.

Checking TX adjustments at TP5 (L23/AM) is adjustable but on SSB TP6 (L24 L25) the frequency readings jump all over.

Radio sounds OK on AM but SSB is unintelligible.



It occurred to me that my FC may have a problem and I should compare the readings of my DX 949.

TP2 voltage was a little low.
IC3-8 was a little off but close and I didn't want to break the seal on VC1.
Adjusted RX AM and SSB (L20/21/22) to spec. (slightly off)

AGAIN!!!, unable to readjust VR7 to 16.267500 MHz. Reads above 16.27 and again pot is completely CCW.

Again checking TX SSB (L24 L25) at TP6 the frequency readings are jumping around.




What is going on? Two radios with the same problem?



Just for grins, I tried setting the TP2 voltage back to where it was originally (2V). But SSB TX at TP6 (L24/25) are still unlocked.
 

most likely your freq counter is loading down the circuit and giving you a false reading.
then you adjust for what seems like a good reading but is not.

when the freq counter jumps around like that, it usually means that the signal from the radio is not strong enough to drive the counter.

what kind of counter are you using?

i will look at the alignment procedure and see if i can come up with anything else.

for now, try putting a .01uF cap on the positive lead of your counter probe.
touch the other lead of the cap to the test point and see if that gives you a different reading on your counter.
this helps keep the counter from loading down the circuit and causing erroneous readings.

tell me what you come up with and i will get back to you.
LC
 
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Thanks a lot! Will get back to you with the brand/model and will try the blocking cap.

Noticed that your TP2/L14 is 3 VDC compared to the factory service manual of 2.5 VDC. I'll try changing that also.
 
You were right, the factory service manual had a typo. It said to use AM TX to adjust TX OFFSET and it should have said LSB TX. Your on-line instructions tipped me off. THANKS!

Now I have a new problem. SM says to TX on AM and measure AM OSC at TP5, this freq jumps around 100s of Hz and a blocking cap does not help. I centered it roughly and went on to adjust L/USB OSC. Both lower and upper side band have no readings at all at TP6 on BOTH radios.

BTW, my FC is a Fluke 1910/1911, cal lab at work says it is on freq.
Fluke 1910 specifications
 
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Just posting this to help people out . Mike’s radio repair channel which is still on YouTube but no longer active has a great answer to most people’s problems when doing radio alignment with frequency counters. Basically it is a small preamp you can buy on eBay or Amazon that you hook up from the test probes in and the out side goes to the counter. Works perfectly and I bought one and use it for the exact reason that is talked about here. The signal is too weak unless you have an expensive counter so adding this little guy inline amps up the signal with no harm done to anything and you can read those frequencies that you never got a reading on before. Totally changed the game for me check it out
 
We have learned to use the "social distancing" model to set internal frequencies in this kind of radio. We listen with a calibrated monitor receiver. The simple act of clipping a 'scope probe to a crystal-oscillator circuit tends to load down the circuit, and change the frequency. The trimmer on the crystal gets set for the desired counter reading, but when the probe is disconnected the actual frequency jumps up from what it was with the probe connected.

In the bad old days there would be a one-transistor 'booster' or 'buffer' circuit following a crystal oscillator. Probing the counter on the output of that transistor would isolate the probe tip's capacitance from the crystal, and permit an accurate setting. Newer radios with PLL circuits almost never include this feature.

A ham radio that's calibrated to WWV may work out better. A coax jumper with the shell backed off the far end will get you a sniffing antenna to hold near the circuit that's being calibrated. Even if it's not good enough to use as a reference you can tune in the crystal's carrier in SSB mode, setting for a comfortable tone pitch. Connect, then unhook the counter's probe on that circuit and see if you hear a change in pitch. This will reveal if your probe is introducing an error.

And if that's not the problem, this fault lies elsewhere.

73
 
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Just read your post and was wondering if you read mine and either agreed or tried it. Just saying it works when you follow alignment info and have a low or no signal on the freq counter. Requires 12 volt input on it but that should be easy for most folks
 
And I was never claiming to be a pro by the way just been in the hobby for 30 years and with the internet if you look deep enough a lot of the times you find smart answers and I can definitely say it works
 
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The amplified probe is a cool idea, but the same rule applies. The tip of a probe always has some capacitance to ground. Is it enough capacitance to disrupt an adjustment when the tip is unhooked from the circuit, or does it make no real difference at all?

Just listening the the frequency being adjusted, first with the probe attached, and then with the probe unhooked would settle the question, at least.

And if you don't have a ham or shortwave receiver handy to do this, it's not terribly helpful advice.

73
 
Just read what you posted and not really understanding what you mean. If I unhook the probe it would go back to zeros on my freq counter. It doesn’t radiate a signal if that’s what your saying. It’s really just a preamp in a little circuit board with BNC connectors on each side for rf in and rf out. I’ve used it as a preamp and works as good as any I’ve ever had but I saw the guy talking about not having enough signal sometimes when doing alignments and he explained that it was an easy way to get results so I bought one cheap. Had to be powered with 12 volts to work.
 
I don’t post much on here but I like reading good info from guys that know more than I do and I have a problem with a galaxy dx 2547 that maybe someone could give me a possible suggestion. Ok so picked up the radio off eBay and worked fine which was nice and first thing I did was align the pill and transmit which went perfectly fine and it was definitely needing that. Next I wanted to do a channel mod and didn’t really like the way the frequencies were laid out after so I decided to put the viagra b board in it. Oh and before that I did unlock the clarifier and that wasn’t too hard besides the fact that everything on the board is really tiny so kind of a pain in the butt . Then installed the viagra board and checked over what I did carefully with a magnifying glass to make sure everything looked good. Next I turned the radio on and got 40 up and 40 down just the way I wanted but following the alignment after didn’t quite work with tuning the pots on the viagra. Frequencies weren’t aligning properly so I decided to take it out and I’ve read other people saying it’s not good and had caused problems with their radios. So basically I was sorry I bought it but I undid everything I did and made sure all looked good then tried to align the radio again and now on USB I have a carrier of 40 lbs with an antenna plugged in but none when I take it out. The pot L21 will not adjust at all now. Lower sideband seemed to align ok but I can’t tune anyone in at all . Forgot to add the part where I undid the clarifier mod thinking I’d just get it back to stock besides giving it a good peak and tune which worked well. Am receives and transmits fine and is on freq. Lsb aligned properly but can’t tune people in now and USB is a complete disaster! So I’m guessing maybe I fried a diode or many I really am stumped. If anyone agrees or has a better idea please help Can’t get good test results without unsoldering a leg and these thinks are really tiny and a pain in the ass to work with but I will if anybody thinks thats where I should start. Sorry for the long post just wanted to give all the info and the board is EPT069611A, which is different from cbtricks but everything is pretty much the same I believe as far as I’ve seen. Thanks guys and bright ideas would be awesome
 
n3umw said:
I have two radios (DX2547 AND DX949) with the exact same problems
1) VR7 (transmit offset) is not adjustable to spec
2) AM is OK, but SSB is unintelligible.

--------------

On July 5th, 2010 I ordered a DX2547 radio as a match for my 5 year old DX949 mobile.

A week after receiving the radio I noticed the SSB receive frequency had drifted. I left the radio turned on 24/7 to see if there would be additional drift.

After a week of burn-in, it had drifted so far that the clarifier had to be turned completely CCW to be at the center receive frequency. Not sure what the transmit frequency was doing as there is currently little SSB activity in my area. Listening on my HF rig, SSB audio sounds funny but hard to tell. After several weeks radio seems to have stabilized.

I have the factory and Lou Franklin service manuals so I decided to open it up and realign the PLL circuit.

Warmed it up and removed TP7/8/9 PCB.

The voltage at TP2 was quite a bit below 2.5VDC, but L14 readjusted OK.

No scope available for the L15 adjustment.

Adjusted VC1, L20/21/22 to RX spec. using external frequency counter at test points. Internal frequency counter is now centered.

Unable to readjust VR7 to 16.267500 MHz. Reads above frequency (from 16.2693-16.2721) and pot is completely CCW.

Checking TX adjustments at TP5 (L23/AM) is adjustable but on SSB TP6 (L24 L25) the frequency readings jump all over.

Radio sounds OK on AM but SSB is unintelligible.



It occurred to me that my FC may have a problem and I should compare the readings of my DX 949.

TP2 voltage was a little low.
IC3-8 was a little off but close and I didn't want to break the seal on VC1.
Adjusted RX AM and SSB (L20/21/22) to spec. (slightly off)

AGAIN!!!, unable to readjust VR7 to 16.267500 MHz. Reads above 16.27 and again pot is completely CCW.

Again checking TX SSB (L24 L25) at TP6 the frequency readings are jumping around.




What is going on? Two radios with the same problem?



Just for grins, I tried setting the TP2 voltage back to where it was originally (2V). But SSB TX at TP6 (L24/25) are still unlocked.
Click to expand...
Imagine this all these years later I have the same problem did you ever solve the problem getting your sideband frequencies adjusted
 
If you hover the mouse cursor on a member's avatar, it will display the last time that member visited this forum. For Desperado505 it says "Last seen December 29, 2021".

Doesn't look like he'll see your reply or answer it unless he just pops in out of the blue after a year and a half.

And if you're having this sort of problem, post a new thread with a description of what's acting wrong, and what tools you may have to try and set it right.

73
 
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