[Elecraft] sidetone mod now works

[G3SJJ]

I did the mod recently on my K2/100 serial 5545. It made a big 
difference and now the sidetone is much more relaxing to listen to. I 
didn't enjoy txing on the K2 before this. This is what I did :

1 - Remove L1 and C33

2 - Solder a 2.2uF in place of L1

3 - Cut a small piece of holed circuit board to 23mm x 10mm

4 - Mount L1, a 120 ohm resistor and a 0.68uF capacitor on the board

5 - Cut appropriate tracks so that a series network is formed

6 - Solder two lengths of bare solid wire 1.5cms long to the board, 
coming out of the component side

7 - Solder the board into C33 holes, so that the components are facing 
the control board.

This allows two things. One is that there is no track to cut and the 
other is that you can adjust the components on the small board easily if 
required

I check before and after using Spectrogram and the sidetone harmonics 
have definitely been reduced.

Chris G3SJJ



    Sverre Holm wrote:
>> My L1 82 mH inductor has a DC resistance of 62 ohms. This is quite different from the 180 ohm version used in the mod. Would a series resistor be desired as Fred indicates in the message below? I have 100 ohm, 120 ohm, and 150 ohm resistors on hand. Where is this resistor installed between U10 pin 7 and the inductor or between the inductor and C33? What type of capacitor would be best suited for this mod? My junk box only has 1 uF 100 V 5% metallized polyester or 2.2 uF 16 V 10% dipped tantalum capacitors. The polyester caps are rather large. A couple of the 2.2s in series would be 1.1 uF. 
>>
>> Darrell,
>>
>> I did the TF3MA sidetone mod some months ago on my K2 serial #2198 and I am
>> very pleased with it. See my comments on 
>> http://www.ac6rm.net/mailarchive/html/elecraft-list/2006-12/msg01043.html
>> where I wrote that "This mod really works wonders with the sidetone quality
>> of the K2". I had done the sidetone upgrade to the 3000+ model previously,
>> but this latest change still was very worthwhile doing.
>>
>> You should add series resistance to the inductor. If I understand your
>> question right, the order, L+R or R+L, doesn't make any difference. I would
>> try the 120 ohm resistor giving you a total of 120+62 = 182 ohms. Maybe the
>> size
>>
>> I would probably have tried with the series combination of two 2.2 uF
>> tantalum capacitors in order to avoid putting the large 1 uF capacitor in
>> there.
>>
>>
>>
>> 73
>>
>> Sverre
>> LA3ZA
>>
>> Unofficial Guide to K2 Modifications
>> http://www.qslnet.de/member/la3za/K2/mod.html
>>
>>