[Elecraft] K2 SSB, "Hi Cur" message on PTT

[Doug Heacock]

Thanks, Don--I do have the same symptoms when I connect paddles and hit the
dot paddle in SSB mode--I'll try the adjustment you recommended and keep
working at it.

73 de aa0ms

On Mon, Feb 8, 2010 at 6:08 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:

> Doug,
>
> Start with the easy things first - it could be RF Feedback or some type of
> oscillation in the mic itself - or it could be a lack of carrier balance on
> the KSB2 board.  To check quickly, do not connect a microphone at all - just
> connect your paddles to the key jack, and in SSB mode, close the dot paddle
> (the DOT line inside the K2 is the same as PTT).  Do you have any power
> output?  You should not because there is no audio.  If you do have RF
> output, the first step is to adjust the carrier balance pot on the KSB2
> board for minimum RF - you may have to compromise between LSB and USB, but
> the carrier level should drop to a very low level at the correct adjustment
> point.  That point should be near mid-range on the pot, if it is not, then
> look for a problem.
> Once you have the carrier balanced, it is time to try the microphone again
> - since you now know the carrier balance is correct, this time suspect RF
> Feedback (or audio feedback if you have a computer soundcard also connected)
> if it happens when the mic is added.
>
> There are other possibilities such as a problem in the ALC section of the
> KSB2 board, but try the above before doing anything else.
>
> 73,
> Don W3FPR
>
>
> Doug Heacock wrote:
>
>> I dusted off my old K2 recently and decided to try to wire up an electret
>> mic and give SSB a try--I've had the SSB module since I built the K2 years
>> ago, but just never used it, because I had no mic at the time.  I've
>> discovered that when I ground the PTT line with the K2 in LSB or USB mode,
>> I
>> get the "Hi Cur" message, and my output power goes to well over 15W,
>> regardless of the setting of the power output control.
>>
>> I've done some of the voltage checks recommended in the SSB module manual,
>> but only those for RX mode--I'm a little nervous about trying to measure
>> voltages in transmit mode, because I don't know how long the PA can take
>> that kind of current, and I don't want to fritz the final or cause other
>> problems.  There are some voltage discrepancies associated with U2--pin 5
>> on
>> that device is supposed to have 0.6v in RX mode, but I'm seeing more like
>> 2.5v.  Pin 3 of U4--same story.
>>
>> If anyone out there has any suggestions for where to look for problems, or
>> how to do further testing, I'm all ears.  I found an old thread in the
>> list
>> archives that suggested replacing Q3 and/or Q4 on the K2 control board, in
>> case one of those 2N7000s happened to take a static electricity hit, but I
>> haven't had a chance to do that yet (don't have any 7000s lying around),
>> and
>> I'm somewhat hesitant to go down that path because this rig seems to work
>> just fine in CW mode.
>>
>> Many thanks, Doug
>>
>>
>


-- 
Doug Heacock
Director of Media and Communications
Contemporary Worship Leader
Lawrence Free Methodist Church
Lawrence, KS
dheacock at lfmchurch.org
http://www.lfmchurch.org