[Elecraft] K1 no xmit

[Brad Hedges]

Gang,

I posted here a couple of weeks back with problems - no xmit on my new K1-4.
I can get 15M to peak at about 1/2 watt, but nothing more than the 0.1 w
baseline anywhere else. I can peak the trim caps, but still nothing. I was
able - once - to get 30M peaked, but then lost it shortly afterwards. I
hooked up with a local ham/tech and here is his report:

Brad


Well I have had no luck.   I got about 1/2 watt on 21 mhz but the other
bands still have no measurable power out on the Welz..  I suspect the U7
premix mixer or the input to U8..

Probably like you, I have measured dc voltages and resistances cursor
checked component placement, retouched solder joints.  But still no change.
I rechecked all the resistance values for the filter board to make sure the
relay coils and norm closed are ok...  All IS OK. I double checked the
filter selection vs. band selection, the b1,b2, that is selecting ok.

Using his email as a checklist I don't get past first-base: 1.  The premix
osc output from the filter board seems fine, its a simiple xtal osc ckt
works ok. 400mv rf same as his. <NOTE: checklist from Gary at Elecraft.
Brad>

2.  But the balanced premix out (U7 pins 4,5) of the main board to the
filter board is very low...  It is a balanced output, and I dont know what
the level should be there??  I think I have good vfo.  90mv p/p output.  If
its low that could be why the output is low...

I have scoped (15mhz bandpass Tektronix) the output at the antenna and get
enough signal to peak all those filter board caps, but still no power out
except a 1/2 watt on 21 Mhz.  I scoped the antenna to reduce the possiblity
of loading the circuit with my 10x probe.

Each of those caps peaks the tiny output at the antenna.  I have been over
and over tuning those.

So contact those elecraft fellers and see what they say about the low output
from the U7.

The U7 premix has 90 mv p/p from vfo in on pin 1
                 400 mv p/p from filter board xtals on pin 6

but on pin 4 and 5 the ouput of the bal mixer is less than 20 mv p/p on each
pin.  HOW MUCH RF is supposed to be here????  Can I even measure it with a
10x probe..  Yes, I took into account to multiply the screen times 10...

This feeds the filter board, but on P1 pin 6 the premix output to the tx
mixer/osc I have almost nothing....  Maybe being loaded down somehow, or the
U7 is bad..  Unfortunately there are no U8 voltage measurement on page 7, so
If its loading down the input???

U7 dc voltages match page 7.

I peaked those caps as best as I can....  I'll have to drag it to work and
put on the hp8920 to check see if the rx sens is bad.

See what they say...
Dick


Any and all help MORE than greatly appreciated!
Brad
K0BHC