[Elecraft] K2 no TX on 20m&30m, no sidetone. after KIO2 upgrade. Any Pointers?

[Don Wilhelm]

  John,

I doubt that you did anything on the Control Board to cause this problem.
20 meters and 30 meters share part of the bandpass filter and the entire 
Low Pass Filter.
Check the Low Pass Filter first.  Since it receives weakly on both 
bands, try connecting an antenna center conductor through a .001 uf 
capacitor to a couple points in the K2  - first get a "level set" by 
connecting to the AUX RF connector (the pin toward the inside of the K2 
- if the signal is louder than at the KAT2 antenna jack, then the 
problem is in the KAT2 (did you inadvertently set those bands to ANT2?).
The next point is the W1 jumper (or pin 1 of the K160RX if installed).  
If the signal got louder, the low pass filter is the problem area.
Next is the W6 jumper (or pin 3 of the K60XV option) - this bypasses 
both the LPF and the T/R switch area.
If you still have low signals there, you can conclude that your problem 
is likely in the bandpass filter.  To verify, touch the capacitor to the 
cathode of either D6 or D7 - you will likely hear a lot of extraneous 
noise because you have bypassed any receiver front end filtering, but 
the relative strength of the signal should indicate where the problem lies.

73,
Don W3FPR


On 9/30/2010 10:41 AM, EI7GN wrote:
> Hi Guys, My K2 serial#01291, with KSB2, K160RX, KNB2, KAF2, KAT2, KBT2,  Rev
> A control board.
>
> 2 days ago i decided to build the KIOS that has been sitting on the bench
> for a year now. I took a full day to build and fit same. I removed the
> control board and did the sidetone mod (cut trace) with the two link wires
> and cap. On the back of the control board thier were two large resistors in
> series (83ohms each) soldered together bent over and heat shrink around
> them. They were soldered to RP5 at pins 7&  10 at least it looked like 10 as
> it was broken away and not connected or I may have broken it away during
> dissasembly. Anyway I soldered to 10. I reasembled the radio with the new
> KIOS.
> I changed the sidetone in the menu and got side tone.
> Next I noticed Lo P indicated when I try to tune auto atu on 20m or 30m
> only. No output. all other bands ok.
> Also receive is very very weak on 20m&  30m, all other bands ok.
> I thought maybe the two resistors should have been disconnected, so took
> them out. no difference.
> Then thought maybe a problem with the cut trace mod i did on ctrl board.
> Reversed that no change.
> So put the resistors back, no change. Last thing I did was take out the
> resistors. I now have a barely audible sidetone that must  have happened
> somewhere in the last few steps.
>
> Looking at the circuit I think 20m&  30m share bandpass filter, maybe i
> damaged it with the cable from the KIOS when I put the lid on with the new
> cable?
>