[Elecraft] K1 80/40 tx problem

[Don Wilhelm]

  Igor,

The waveshapes are normal.  They will not be anything like a sine wave 
coming out of a mixer, but the fundemental RF voltage is still present, 
so the waveform will be cleaned up by the bandpass filters and the PA 
Low Pass Filter.

Since you have excessive current draw, the first place to look is the 
Low Pass Filter on the 2 band board.  Are the capacitors correct?  Are 
the number of turns on the toroids correct?  Count the turns carefully, 
counting each turn that goes through the center of the core - a straight 
wire through a toroid is one turn, a full wrap around the core is two 
turns.  Failure to realize that fact is a common builder error.

73,
Don W3FPR

On 9/26/2010 12:06 PM, Igor Lána wrote:
> Hello friends,
> I built a kit K1 80/40. Everything was no problem. All values of resistors
> and DC voltages were OK. But in chapter 9, part "Band 1 Allignment",
> transistor Q7 has been melted (2W at 80 m band).
> I changed it and after that I measured current -  0.1 W on 3.6 MHz current
> is 1.1A! On 7 MHz, is slightly better - 0.1W  is 0.4 A but the 2W is 1.3 A.
> After several attempts to find mistake, I tried to use the "Signal
> Transmitter tracing" with DRV-ground jumper. Instead of RF Probe  I used the
> old oscilloscop in multimetr mode. I performed the measurements to the point
> 15. All values looked like okay, but from the point 10, I watched the
> unstability.
> I switched oscilloscop to the measurement curve mode. And on OSC it is not
> pure sine wave. The point of MIX has been very vibrant.  ATTN is clean. I do
> not know if  the problem is on 6-7 intputs U8 or output 4.
> Please, see videos of measuring on youtube.
> ociloscop 150ns time raster: http://www.youtube.com/watch?v=fYTOw9DWfKI
> ociloscop 50ns time raster: http://www.youtube.com/watch?v=9mUunLQdBuU
> ociloscop-multimeter: http://www.youtube.com/watch?v=oFaKCssXsA
> In every video first part is on ATTN, second on OSC, and the third on MIX.
>
> Please, do you have some recommendations how or where to find the error?
> Can Xtal X6 defective?
>
> Thanks
> 73 Igor OK1TGI
>
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