Alignment Question - Problem

[loosecannon]

this is a very common problem with this chassis.

many times ive been able to get it to work correctly, but a couple of times i had to set "center" a bit off from true center of the pot.

i usually use a 10 turn pot when doing these clarifiers, and if you are willing to have only 4 turns up and 6 turns down (instead of 5 in either direction) then you can get the clarifier to center up nicely and have 6+ KHZ of slide in either direction.

if you want to try to keep the stock pot centered, the values to play with are R174 and R175.

+8 volts sets the top range. no increasing this unless you want to use an external regulator like a 7809.

R175 sets the bottom range. lower its value for more down range.
dont go any lower than about 100 ohms for power supply protection.
(i usually replace R175 with a diode for max range while still protecting the power supply)

R174 sets the "center". playing with its value will shift the center of the clarifier range.
i usually use a jumper here, but again im using 10 turn pots.

you dont need to keep replacing components, your radio works fine, they are just like this.
LC

 

[Robb]

Grinder74:

If and when I find a solution, I'll post it ASAP. This has been driving me NUTS !

Sounds like you are the opposite of mine.....I am moving the core UP and run out of change. You are bottoming out.......strange.....

These coils will change freq both up and down when the adjustment ferrite in the tuning coil is moved from the center point in the coil. IOW - the freq will go both up and down two ways. Experiment with that idea and you will see. This might even solve your dilemma . . .


Oh yeah; check the sweep of the clarifier knob to be sure it is sweeping ~130 degrees turned left and right against the center point - too . . .

 

[sdmahr]

What really gets me is that LSB and AM are perfect. The cores in the cans for LSB and AM are about "center", (up and down), when they hit the spec'd frequency. Its just the USB that is off. With the USB, the frequency gets to its lowest point, (toward the target), just as the core evens up with the top of the can, then it skyrockets again upward AWAY from where it needs to be if you move it up or down from that point. The lowest it will get it not low enough to meet the requirement.

Since I'm not a USB user, I'm tempted to just forget it and use it on LSB like I normally do. If I ever sell it, the buyer won't be happy its not "fully functional".....and to be honest it drives me nuts it doesn't work.

On TP1, Channel 19, the target frequency is 34.9865. I consistently cannot get any lower than 34.9907. (and that is with the core even with the top of the can, any higher it shoots up, any lower and it shoots up) I cannot even get there if I crank the clarifier all the way over.

I've switched out most components related to the USB/L59 circuit when USB is selected on the switch. I've tried different cores in the can and flipped the cores over with no change. All I have left to change it the can....if I had one I would try.

I'll do some signal changing this weekend, but I believe the signal goes goofy going through L59. I'll confirm or deny that when I check.

 

[loosecannon]

sdmahr, in case you missed my last post; you are most likely not experiencing a "repair" issue.
like i said, this happens with clarifier mods to this chassis all the time; and ive done a lot of them.

when the slug gets even with the top of the can, that is the coil's "maximum inductance" setting.
any higher and the inductance starts going down again.

first thing to check is what has been done to the clarifier as far as modding goes.

here is the way is should be:

remove D52 and R44.
move the "hot" wire on the clarifier pot to pin 1 of the MB3756 voltage regulator.
replace R174 with a jumper wire.
change R175 to approx. 100 ohms. (you can play with this value in order to get more "down slide" but dont go any lower than 47 ohms. again you can also change it to a diode to maintain power supply protection.

after this is all done, you may still find that USB is hard or impossible to center up.

the way to deal with this is to either pull the clarifier knob off, turn the pot until you can put all three modes on freq. and then put the knob back on with the notch on top.
no, this is not the ideal method, and i dont like doing it. in fact the only time ill do it is when im using a 10 turn pot. (i highly recommend using one as it makes it so much nicer)

or, you can start playing with the varactor diode D35. i like using the stock one, but if you put a little inductance in series with it (like around 3.9-5.6uH)
you can increase the slide range which might allow you to center up all three modes.
LC

 

[sonoma]

what LC said is probably what you will run into with some radios. the choke that is in the circuit can be played with also.just because LSB and AM are fine does not mean a lot. since the clarifier is opened up you will have to make sure it was done right and see what you have to do to make the change. I hate when this happens. I have a president teddy r that was off some on freq and I had to even add a cap to the circuit to get it on freq right. even with it being a AM only radio. changed the crystal and caps and like I said I had to add one to one of the tuning coils to get it on freq. it was about a 30pf across the can contacts to get it right.
a few months ago I had the same problem with a teaberry 40 channel am ssb radio and had to play with some caps on it to get all 3 to alighn.

 

[unit_399]

sdmahr -

The winding in L59 is center tapped, but two of the three pins are shorted together so that only 1\2 of the winding is utilized. By modifying the board as shown below, you can isolate the center tap and utilize the entire winding in the coil. This will increase L59's inductance and should allow you to tune the proper USB frequency. Good Luck...73s.

- 399

 

[sdmahr]

what LC said is probably what you will run into with some radios. the choke that is in the circuit can be played with also.just because LSB and AM are fine does not mean a lot. since the clarifier is opened up you will have to make sure it was done right and see what you have to do to make the change. I hate when this happens. I have a president teddy r that was off some on freq and I had to even add a cap to the circuit to get it on freq right. even with it being a AM only radio. changed the crystal and caps and like I said I had to add one to one of the tuning coils to get it on freq. it was about a 30pf across the can contacts to get it right.
a few months ago I had the same problem with a teaberry 40 channel am ssb radio and had to play with some caps on it to get all 3 to alighn.

Ceramic caps I assume ?? Across the non-grounded side pins ??

I tried some caps across these terminals but then the frequency shot up to 36.XXX Mhz.....so I removed them. Perhaps I was using the wrong values ????

 

[sdmahr]

what LC said is probably what you will run into with some radios. the choke that is in the circuit can be played with also.just because LSB and AM are fine does not mean a lot. since the clarifier is opened up you will have to make sure it was done right and see what you have to do to make the change. I hate when this happens. I have a president teddy r that was off some on freq and I had to even add a cap to the circuit to get it on freq right. even with it being a AM only radio. changed the crystal and caps and like I said I had to add one to one of the tuning coils to get it on freq. it was about a 30pf across the can contacts to get it right.
a few months ago I had the same problem with a teaberry 40 channel am ssb radio and had to play with some caps on it to get all 3 to alighn.

FYI: The clarifier mod done to this radio is one of Robbs favorites: Lift one leg of D58 and power wire to voltage regulator. Do you think a more radical or different approach to the clarifier mod would help??? (as listed in this thread??)

 

[sdmahr]

sdmahr -

The winding in L59 is center tapped, but two of the three pins are shorted together so that only 1\2 of the winding is utilized. By modifying the board as shown below, you can isolate the center tap and utilize the entire winding in the coil. This will increase L59's inductance and should allow you to tune the proper USB frequency. Good Luck...73s.

- 399

View attachment 12853

399: I tried this and saw no improvement in the frequency obtainable with adjustment of L59. Thanks for the input.

 

[sonoma]

I have some variable caps I some times have to use to get what I need on the bottom of the can to see if that helps.Robbs mod works on most radios but you may have the exception to the rule. I have even had to put a choke off the diode to help. there is so many variables that can cause what you are having a problem with. I have even had to do the mod 399 posted and put a diode across the trace to help. I was trying to find my copy of this for you but 399 found his 1st. I even have one to rebuild the can and add some surface mounts on the board below the can. but do not want to get you into that. I thought the mod 399 would have taken care of your problem. ever so often I have ran into the malaysia built radios that causes a lot of problems trying to correct the problem. do not know why but have over the years.

I have even cut the trace to the can and added a cap to the trace side on some. do not have a good solution for you so far. you can try Loosecannons mod for the clarifier to see if it works. have you tried putting it back to stock to see if it will align? even the latest version of the radio sometimes plays havok with the radio when you try the clarifier mod. on the newset versions you have to watch the voltage to make sure it is around 5 volts and not the 8 volts feeding the clarifier. this is only on the last ones built.

 

[unit_399]

Do this test to determine if the clarifier range is correct , and that the clarifier control is actually centered when tuning L22, 23, and 59.

Connect a counter to TP10. Rotate the clarifier over its full range. The frequency should only vary by +/- 1 khz or so. Whatever the range turns out to be, do the math and adjust the clarifier to the exact center of the range.
Then redo the alignment of L22, 23, and 59. If this doesn't fix things, I'd check crystal X3 (11.325 mhz) in a crystal tester to see if it's on freq or not. 73s.

- 399

 

[sdmahr]

I have a fairly large supply of capacitors available. If I were to put a fixed ceramic or variable cap, (2pf - 30pf range), on the board for influencing the frequency, where would you put it on the back of the board ??

In other words: Where does the fixed or variable cap go to influence the frequency ?? Across the hot pins of the coil?? Hot pin of coil to ground ? In series somewhere with another component ??

I also have axial inductor coils.....it was mentioned perhaps to add one in series with D35. I have some at 5.6uH.....good place to start ? Does it matter which side of the diode it is connected to ? Schematic shows the diode parked between ground and the feed into the 11.325 MHz crystal. So does it go on the ground side or crystal side of the diode?

Sorry for all the questions. You electrical guys have to help me out ! I'm a Mechanical Engineer and I am a bit out of my league ! ! (But I love learning and making stuff perform right ! !)

Thanks again for your patients ! !