Texas Ranger TR 966/ Galaxy 949 PLL alignment question

[Lkaskel]

Hi Gang,
I am aligning a TR966 which has the same board as the Galaxy 949. In the PLL alignment instructions all is good until the last 2 steps. That is the USB and LSB TX OSC alignment. The instructions say to attach to TP6, transmit the radio and align to a specific frequency. When I place the radio in TX it does not trigger my freq counter (HP5370B- calibrated). I am unsure how to get it to trigger. I tried adding the double tone, no luck. I tried re-installing the bias jumper, no luck. I am sure that there is something I am missing or the instructions are incorrect. I already found one issue where it was asking you to set the transmit freq offset on channel 1 am and it was supposed to be channel 1 LSB. Has anyone aligned one and know the "trick"?



Thanks in advance!!!!

 

[Robb]

The trick is to not use those TP's because of this triggering problem issue.

I use a RF sampler at the dummy load to check the output transmit freq. Using a 1khz tone into the mic on upper or lower SSB, the radio can be adjusted for 27.184000mhz for LSB/ch 19 and 27.186000mhz for USB. Works perfectly; might take a little practice, but not hard to do.

https://freesound.org/people/klangfabrik/sounds/28636/

 

[Lkaskel]

The trick is to not use those TP's because of this triggering problem issue.

I use a RF sampler at the dummy load to check the output transmit freq. Using a 1khz tone into the mic on upper or lower SSB, the radio can be adjusted for 27.184000 for LSB/ch 19 and 27.186000 for USB. Works perfect; might take a little practice, but not hard to do.

https://freesound.org/people/klangfabrik/sounds/28636/

Robb,
That worked perfectly!! Thanks for helping me realize that there is a trigger issue and I'm not 100% crazy. Maybe just 50% . Here is one other question that you may be able to help with. As I align this radio it seems to drift like crazy. I can align it dead on, walk away, and 15 minutes later it has drifted out of spec. It is at room temp and has been on for a few hours. I can re-cap it but the owner does not want to spend the money right now and I am unsure that it will fix the drifting issue anyway. Any thoughts? I have heard that these radios are "prone" to drifting but is that normal?

 

[Robb]

a) Galaxy does use cheap xtals. The 15.360 xtal might be bad. Check C132 to be sure that it isn't going bad first.
b) Check the voltage regulator and be sure that it is stable. Check C170 that it is good too.
c) The 10.240 osc xtal can also be dicey.
d) C91; change it out to a 470uf/16v or higher if it is bad.

That should be a fair starting point. If the caps are old or just failing, he may have to bite the bullet and get the whole thing capped.

If the radio had the clarifier range extended; then put it back to stock slide range. Extending the clarifier range in these radio is like inviting sharks to a shipwreck.

 

[ExitThirteen]

Method 2:

Another way you can set the offset cans is to adjust the SSB carrier balance until you get a carrier, that will also trigger your counter. When I get done adjusting the offset cans, I simply re-adjust the carrier balance pot until the carrier is null.

~Cheers~

 

[loosecannon]

setting the offsets is kind of an art.

Kopcicle got me thinking about it, and while i have been doing it 'right' for a long time, his suggestions have improved my alignments. (much appreciated brother!)

What kopcicle brought up was that if you are aligning the offsets exactly for the freqs in the service manual, you are not taking into account the fact that the filter itself might not be even.

this is easy to hear when you do a radio this way. you change to LSB and it has a distinct sound to it, then you turn to USB and it sounds different, as in a higher or lower 'tone' to it.

this is because the filters aren't perfect and we shouldnt expect them to be.

so now, i start by getting them close using the process Robb suggested using a known accurate 1K tone.
then i set the sig gen to AM mode with a 1K tone into the radio.
now switch back and forth from AM to LSB noting the difference in audio freq.
tune the LSB offset so it matches up with the AM mode. kind of like tuning a guitar.
do the same for USB.

well what does the crowd think?
LC

 

[ExitThirteen]

Kop is right.

And as such, I've been tuning it by sound rather than actual frequency for several years. Yes, usually one sideband will not line up and sound the same as the other. So I line up my sidebands to where they sound audibly equal in both TX and RX. Usually they're pretty close to where they should be, frequency-wise, but they won't be totally spot on. But if you're running an unlocked clarifier, this will not matter much anyhow.

~Cheers~

 

[Lkaskel]

Method 2:

Another way you can set the offset cans is to adjust the SSB carrier balance until you get a carrier, that will also trigger your counter. When I get done adjusting the offset cans, I simply re-adjust the carrier balance pot until the carrier is null.

~Cheers~

I did try to adjust the SSb balance (VR6) as I had read that this was the intended method but it did not trigger either counter. Both are great counters and calibrated so I was feeling like it might not necessarily be the issue hence my challenge. Interestingly I have a Saturn Turbo in for alignment and I threw that on the bench as a test knowing that it was a similar board. I had the same issue with it. Most areas of the PLL alignment worked like normal but the offset would not trigger the counter. This is the 1st time I have worked on these boards and also had this problem so I am still trying to understand the reason for no trigger. I like that using the sample port works as a second way to accomplish this.

 

[loosecannon]

lkaskel,

the signal levels there are just too darn low for the counter to pick up.
not to mention that you can easily load down these circuits with your test probe.

when tuning SSB offsets its all about centering them in the passband of the filter, and not so much about being right on frequency. theoretically yes, they should all be offset from center up and down by the exact same amount, but in reality, filters end up just a bit imperfect.

you can account for those imperfections by combining the techniques in this thread.

you really will be amazed at the difference doing it this way makes in your alignments.

you will really start to notice that both sidebands now sound the same when you switch between them.
LC

 

[Lkaskel]

setting the offsets is kind of an art.

Kopcicle got me thinking about it, and while i have been doing it 'right' for a long time, his suggestions have improved my alignments. (much appreciated brother!)

What kopcicle brought up was that if you are aligning the offsets exactly for the freqs in the service manual, you are not taking into account the fact that the filter itself might not be even.

this is easy to hear when you do a radio this way. you change to LSB and it has a distinct sound to it, then you turn to USB and it sounds different, as in a higher or lower 'tone' to it.

this is because the filters aren't perfect and we shouldnt expect them to be.

so now, i start by getting them close using the process Robb suggested using a known accurate 1K tone.
then i set the sig gen to AM mode with a 1K tone into the radio.
now switch back and forth from AM to LSB noting the difference in audio freq.
tune the LSB offset so it matches up with the AM mode. kind of like tuning a guitar.
do the same for USB.

well what does the crowd think?
LC

Ok, so this is interesting. I get the USB and LSB alignment close using the 1khz tone injected in the mic input and checking the freq from the antenna/sample port then inject a 1khz signal into the radio/antenna am (30% mod?). Switch mode from AM to LSB and adjust the receive alignment? Sorry that I am not getting this 100% yet!!!

 

[Lkaskel]

One last part of this equation. If I set the freq using the counter and let the radio sit for 30 minutes the frequency drifts 50K - 100K on average. I have set it 5 times today and when I return to the radio AM, LSB and USB are off. The radio is on the bench at room temp the entire time. I have read a lot about these boards (Ranger and Galaxy) and they supposedly "drift" a lot but I have not seen anything like this before.

 

[Robb]

One last part of this equation. If I set the freq using the counter and let the radio sit for 30 minutes the frequency drifts 50K - 100K on average. I have set it 5 times today and when I return to the radio AM, LSB and USB are off. The radio is on the bench at room temp the entire time. I have read a lot about these boards (Ranger and Galaxy) and they supposedly "drift" a lot but I have not seen anything like this before.

You did check the radio for being fully functional before you started the alignment first?

 

[loosecannon]

first, the problems with that particular 966. can you be more specific as to how much the radio is drifting? 50K to me means 50 khz. or did you mean 50,000 hz which would be 5 khz?

we can try a little experiment in order to eliminate the clarifier pot itself as the culprit.
pull J9, which is the header that connects the clarifier control to the main PC board, and then temporarily solder a 470 ohm resistor to each of the outer terminals on the PC board.
now solder both of the leads that are sticking up to the center terminal (obviously do this on the solder side of the PC board.

what you have just done is made a voltage divider that is fixed. your clarifier is just a variable voltage divider.
now check the stability of the radio.
yes, the frequency will be off. don't bother correcting it, just see if it no longer drifts over time like it did before.

if it doesn't drift anymore, that points right to a worn out clarifier control, so replace it.

if it acts just the same, you need to look at the circuit itself, and first suspect would be that 15.36mhz crystal. if it drifts in all modes you want to look for things that are present in all three modes.

as for the alignment itself, don't put the radio in TX to align the SSB offsets.
do it like this: (this is assuming you have already done the previous alignment steps)

set radio to AM mode, channel 20, clarifier perfectly centered, radio already warmed up.
using your RF sampler connected to a dummy load and monitoring the frequency, key the mic (mic gain all the way down) and set L23 for 27.205000 mhz.

now set up a source with a known accurate 1K tone (you can use your freq counter to test it) and set the radio to USB mode. turn the mic gain back up.

inject your 1K tone into the mic, set radio to TX mode, and tune L24 to 27.206000mhz.

now switch to LSB, inject your tone, and set L25 for 27.204000mhz.

set the radio back to AM mode.
now forget all about the freq counter and what it says, and set your sig gen for 27.205000mhz with a 1K tone. inject this signal into the antenna jack and you can hear the 1K tone through the speaker.
now switch to USB mode, and then back to AM mode, and go back and forth until you can tell that there is or isn't a tonal difference between the two modes (like one is higher or lower pitched than the other)
If they are exactly the same, great!
if not (more likely) then give L24 if slight turn and check again.
keep doing this until the tones are the same.

now go to LSB and do the same thing, adjusting L25 for an equal tone.

now you should be able to turn from LSB to USB and back and not notice any tonal difference between the two modes.
LC

 

[Lkaskel]

You did check the radio for being fully functional before you started the alignment first?

I did. It receives, transmits on full power and all its functions work. I thought I was getting into a straight forward alignment but I guess not. I always benchmark a radio before I do anything to it to be sure that I did not cause anything. This radio stuff is challenging at times... I am guessing that it might be a voltage problem. I am going to replace the caps mentioned here and we shall see. I realize the owner cannot afford the work but now I am pressed in and I need to figure this out. Here is an example of the situation.

I set the LSB RX frequency to 16.267500000. It will fluctuate up and down ~2hz each way (267502*** - 267498***) and then it will read something crazy like 267350*** and fluctuate around there. Not slowly drop but drop 150hz in one cycle (1 second) of the counter.

I've aligned many radios with great results and have never seen anything like this.

 

[Lkaskel]

first, the problems with that particular 966. can you be more specific as to how much the radio is drifting? 50K to me means 50 khz. or did you mean 50,000 hz which would be 5 khz?

we can try a little experiment in order to eliminate the clarifier pot itself as the culprit.
pull J9, which is the header that connects the clarifier control to the main PC board, and then temporarily solder a 470 ohm resistor to each of the outer terminals on the PC board.
now solder both of the leads that are sticking up to the center terminal (obviously do this on the solder side of the PC board.

what you have just done is made a voltage divider that is fixed. your clarifier is just a variable voltage divider.
now check the stability of the radio.
yes, the frequency will be off. don't bother correcting it, just see if it no longer drifts over time like it did before.

if it doesn't drift anymore, that points right to a worn out clarifier control, so replace it.

if it acts just the same, you need to look at the circuit itself, and first suspect would be that 15.36mhz crystal. if it drifts in all modes you want to look for things that are present in all three modes.

as for the alignment itself, don't put the radio in TX to align the SSB offsets.
do it like this: (this is assuming you have already done the previous alignment steps)

set radio to AM mode, channel 20, clarifier perfectly centered, radio already warmed up.
using your RF sampler connected to a dummy load and monitoring the frequency, key the mic (mic gain all the way down) and set L23 for 27.205000 mhz.

now set up a source with a known accurate 1K tone (you can use your freq counter to test it) and set the radio to USB mode. turn the mic gain back up.

inject your 1K tone into the mic, set radio to TX mode, and tune L24 to 27.206000mhz.

now switch to LSB, inject your tone, and set L25 for 27.204000mhz.

set the radio back to AM mode.
now forget all about the freq counter and what it says, and set your sig gen for 27.205000mhz with a 1K tone. inject this signal into the antenna jack and you can hear the 1K tone through the speaker.
now switch to USB mode, and then back to AM mode, and go back and forth until you can tell that there is or isn't a tonal difference between the two modes (like one is higher or lower pitched than the other)
If they are exactly the same, great!
if not (more likely) then give L24 if slight turn and check again.
keep doing this until the tones are the same.

now go to LSB and do the same thing, adjusting L25 for an equal tone.

now you should be able to turn from LSB to USB and back and not notice any tonal difference between the two modes.
LC

Ok, I will look at this tomorrow. You are correct in my mistaken account of the frequency. I am suffering from frequency frustration . To be sure we are on the same page. One hz would be the 6th digit to the right of the decimal point (27.000001). Right? I am a little confused at how 50,000 hz is the same as 5khz as you stated. I am about 2 hours past my sleep time so I may not be thinking clearly. It will drop 150hz in one cycle and some times as far as over 1000hz in 15 minutes..

Thank you soo much for your time and council here!!!!