[Elecraft] K3 Audio Upgrade Mod

[Bill W4ZV]

Bill W4ZV wrote:
> 
> ri
> 
> Alexander Ponomarenko-5 wrote:
>> 
>> GA,
>> 
>> today I has same time for install K3-AF-mod (second part with R19 and 
>> R20). It was easy job. Yes, it's really worked! Now line-out are worked 
>> better! Here is plots "before" and "after" mod.
>> 
>> Line-OUT before replaced R19&R20
>> 
> 
> Priwet Alex!
> 
> I believe you have made a mistake.  The 51 ohm resistor should be placed
> ***ON TOP*** of the existing SMD resistors (i.e. in parallel with the
> existing resistors and  NOT replacing them).  Please read the instructions
> more carefully.  
> 
> 73,  Bill  W4ZV
> 

Alex I believe I see what caused your misunderstanding.  On the Main Mod
Kits page, it states:

"Line Out Change: 

KIO3 Main Board: R19/20 (input to line-out transformers) changed from 600 to
51 Ohms to increase line-out low distortion output levels."

http://www.elecraft.com/K3/k3_app_notes.htm 

But on page 8 of the actual mod instructions it says:

"Line Audio Output Modification

This modification reduces the value of two resistors in the left and right
channel line audio outputs on the KIO3 board by
adding 51-ohm resistors in parallel with them. The existing resistors are
surface mount types. Since the new resistors are
wired in parallel with them, it is not necessary to remove the existing SMD
units."

http://www.elecraft.com/K3/mods/K3%20AF%20Stage%20Upgrade%20Instructions%20Rev%20A.pdf

As has been noted by others before, I'm not sure why Elecraft did not
suggest replacing the existing 600 ohm resistors with 47 ohms (parallel
combination of 600 and 51).  Perhaps they were concerned with the problem of
potentially lifting the board traces when removing the 600 ohm resistors.

The documentation on the main mods page (1st link above) needs to be
corrected.

73,  Bill  W4ZV

73,  Bill  W4ZV

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