#4472 transmitter setup problem.

[Jerry Deibel]

I am now doing my transmitter alighment, page 75,  and have a have run into a problem with it.  

On 40 meters when I set the power to 2 watts and press and hold the tune button the power out shown is abt 2.5 on the first hold of tune,  if I do it a second time it comes up abt 2.6 and then if I do it a third time it comes up correct about 1.9.   The cycle contines, it seems that about every three times I press tune I get 1.9.  
The same goes for 5 watts ( 5.8, 6.0 and 4.9) and 10 watts (11.2, 11.4, 9.8).  
The currents look ok,   2 watts @ 1.28a,   5 watts @ 1.7a and 10 watts @ 2.2a (give or take a little depening on the power out.

On 80 meters it's doing  the same.

On 20 meters 2 watts is doing the same, but I get hi current  5 watts and above.

On 15 meters Hi curret on  all 2, 5 and 10  watts.

On 10 meters , the same but here I get max out of only 4.9 watts.

The rf out looks good on a scope.        Dummy load is ok,  SWR 1:1.   I've had a few cw contacts so far.    It's a basic K2.
Has anyone comes across and any ideas?

Also,  is there a way to do a search on the complete archives or do I have to do it by month?

Jerry, N2UZ



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[Don Wilhelm-3]

Jerry,

The variation in power when holding TUNE is not unexpected - it is due to
the transmit ALC settling out.  Yes, the power out is just what the display
says, but it will settle down after several presses of the button.  Not
something to be concerned about.  In normal operation, the power out will
settle down after an initial dash (or about 3 dots) - the ALC resets after a
power request change or after a band change.

The real concern should be the low power output and the HI CUR indications.
Check T1, T2 and T4 carefully for the correct number of turns.  The
secondary winding on T1 and T2 should look just like the diagram in the
manual - this is especially true for T2.  Also, T2 should be mounted a bit
above the board for best performance on the higher bands - 1/16 to 1/8 inch
is fine, and yes the leads will support it just fine.

If you continue to get HI CUR indications, also check the Low Pass Filter -
check the capacitor values and especially the toroids for the correct number
of turns.  When counting turns on a toroid, remember to count the turns
going through the center of the core - you can easily be off by one turn if
you count the loops on the outside.

Finally, check soldering, then recheck soldering, and when that is complete,
double check the soldering!!!

73 and Happy Thanksgiving,
Don W3FPR

----- Original Message -----

>I am now doing my transmitter alighment, page 75,  and have a have run into
>a problem with it.
>
> On 40 meters when I set the power to 2 watts and press and hold the tune
> button the power out shown is abt 2.5 on the first hold of tune,  if I do
> it a second time it comes up abt 2.6 and then if I do it a third time it
> comes up correct about 1.9.   The cycle contines, it seems that about
> every three times I press tune I get 1.9.
> The same goes for 5 watts ( 5.8, 6.0 and 4.9) and 10 watts (11.2, 11.4,
> 9.8).
> The currents look ok,   2 watts @ 1.28a,   5 watts @ 1.7a and 10 watts @
> 2.2a (give or take a little depening on the power out.
>
> On 80 meters it's doing  the same.
>
> On 20 meters 2 watts is doing the same, but I get hi current  5 watts and
> above.
>
> On 15 meters Hi curret on  all 2, 5 and 10  watts.
>
> On 10 meters , the same but here I get max out of only 4.9 watts.
>
> The rf out looks good on a scope.        Dummy load is ok,  SWR 1:1.
> I've had a few cw contacts so far.    It's a basic K2.
> Has anyone comes across and any ideas?
>

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[Jerry Deibel]

 
Found the culprit on hi current,   I had my textronix scope on the output of the K2,  I was doing the xmitter alighment and tweaking the L1 thur L13 cans and left the scope on the output.  It's a 10meg input, don't know why?  I guess it was loading it down??   Will look into it later, I dont' think it should do that.

I disconnected everything and set it up on the work bench to check for bad solder and such and looked at T1 -T3 , they were ok ( i had the torroid guy make them for me)  when i  hooked the K2  back up, everthing worked fine  then I put the scope back on and got  the Hi-current back on the upper bands.

Anyway,    now I adjusted the power out on all band to just shy of hi current( about 2.43ma on the display) and my power out is...
        80 meter = 14.8,   40 meter = 14.8,   30 meter = 13.8,   40 meter = 14.8,   17 meter = 12.6,   15 meter =  11.0,  12 meter = 10,  and 10 meter = 9.4 .

I assume that is ok on all.    

Thanks for all the quick responses  and everyone have a Happy Thanksgiving.

Jerry, n2uz
======= At 2004-11-25, 09:18:00 you wrote: =======

>Jerry,
>
>The variation in power when holding TUNE is not unexpected - it is due to
>the transmit ALC settling out.  Yes, the power out is just what the display
>says, but it will settle down after several presses of the button.  Not
>something to be concerned about.  In normal operation, the power out will
>settle down after an initial dash (or about 3 dots) - the ALC resets after a
>power request change or after a band change.
>
>The real concern should be the low power output and the HI CUR indications.
>Check T1, T2 and T4 carefully for the correct number of turns.  The
>secondary winding on T1 and T2 should look just like the diagram in the
>manual - this is especially true for T2.  Also, T2 should be mounted a bit
>above the board for best performance on the higher bands - 1/16 to 1/8 inch
>is fine, and yes the leads will support it just fine.
>
>If you continue to get HI CUR indications, also check the Low Pass Filter -
>check the capacitor values and especially the toroids for the correct number
>of turns.  When counting turns on a toroid, remember to count the turns
>going through the center of the core - you can easily be off by one turn if
>you count the loops on the outside.
>
>Finally, check soldering, then recheck soldering, and when that is complete,
>double check the soldering!!!
>
>73 and Happy Thanksgiving,
>Don W3FPR
>
>----- Original Message -----
>
>>I am now doing my transmitter alighment, page 75,  and have a have run into
>>a problem with it.
>>
>> On 40 meters when I set the power to 2 watts and press and hold the tune
>> button the power out shown is abt 2.5 on the first hold of tune,  if I do
>> it a second time it comes up abt 2.6 and then if I do it a third time it
>> comes up correct about 1.9.   The cycle contines, it seems that about
>> every three times I press tune I get 1.9.
>> The same goes for 5 watts ( 5.8, 6.0 and 4.9) and 10 watts (11.2, 11.4,
>> 9.8).
>> The currents look ok,   2 watts @ 1.28a,   5 watts @ 1.7a and 10 watts @
>> 2.2a (give or take a little depening on the power out.
>>
>> On 80 meters it's doing  the same.
>>
>> On 20 meters 2 watts is doing the same, but I get hi current  5 watts and
>> above.
>>
>> On 15 meters Hi curret on  all 2, 5 and 10  watts.
>>
>> On 10 meters , the same but here I get max out of only 4.9 watts.
>>
>> The rf out looks good on a scope.        Dummy load is ok,  SWR 1:1.
>> I've had a few cw contacts so far.    It's a basic K2.
>> Has anyone comes across and any ideas?
>>

= = = = = = = = = = = = = = = = = = = =
                       

Best regards.
jerry
[hidden email]
2004-11-25



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[G3VVT]

Jerry,  

Did you use a X10 probe with the scope?
 
The problem could be related to the stub effect at the operating  frequency
caused by the scope leads and the capacitance the scope input  circuit presents
to the K2. Particularly with RF a X10 probe or a high  impedance detector is
just about essential to avoid upsetting the circuit you  are monitoring.
 
The same can apply to checks on the 4MHz clock on the K2 control board  where
the test instrument such as a counter can cause unwanted effects even  though
it has a high input impedance.
 
Bob, G3VVT

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[Jerry Deibel]

Thanks to all who responed.    My original setup was a BNC tee off the K2 with  a 4 foot rg58 coax with bnc on one end and jumper hooks on the other and I then connected the 10x probe to the jumper hook.    
Using just the 10x probe was ok.   It was the added 4 ft coax that caused the problem.

Happy Thanksgiving to all.

Jerry , N2UZ


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