[Elecraft] [K2] No signal at TP1 during Alignment and Test Part 2

[Don Wilhelm]

Robert,

Do you have a good signal at TP3?  If so, ignore the PLL Reference 
oscillator and U4 for now.

You need to get the VFO operating before doing anything else.
Do the DC measurements a Q18.  If you do not have a negative voltage at 
the gate, it is not oscillating.

T5 is the most likely problem with the VFO.  Make certain it is wound 
correctly and the leads are well stripped and tinned.  If you see a ring 
around the lead (on the solder side), that lead was not adequately 
stripped and tinned.  Both windings must be wound in the same direction.

If all the above is correct, put a temporary jumper across C60 to 
disable the VFO ALC circuit.  If it oscillates with the jumper in place, 
but not without it, replace Q17.  If that still does not correct it, try 
replacing Q16.  Be certain D11 is oriented correctly.

Ignore the voltages on U4 pins 5, 6, and 7 - those are digital signals, 
and the manual lists the voltage for the active signal, not what you 
would typically measure with a DMM.  If you look at them with a 'scope 
you can see pulses on those lines, and that should be sufficient for 
proper operation.

RFC 15 also needs to be ignored until after you get the VFO operating. 
Once you get a VFO signal at TP1, then you can investigate the operation 
of U4.

73,
Don W3FPR

On 6/6/2017 9:47 PM, Robert Forster wrote:
> Hello to the group!
> 
> I'm afraid I need to lean on your collective K2 troubleshooting expertise.
> After a long break I have finally made it to the Alignment and Test Part 2
> of my build.  Everything was going OK until I got to the VCO Test.  I have
> no signal at TP1.  I have tested this with the built in counter as well as
> an external counter.  I have gone through some of the troubleshooting I
> could find online:
> 
> The orientation of D13 and D8 look good
> 
> I have checked the soldering at relays K13, K14 and K15 and the value of
> C72.
> 
> I have checked the varactors at D21 through D26 and they are oriented
> properly I am nearly certain they are all the correct type
> 
> I tested RFC15 in the circuit and could not get any continuity through it.
> When I pulled it out of the circuit it tested fine so I put it back in.
> I'm sure this is something basic I just dont understand.
> 
> I know there is some more testing I can do with Q17 and Q18 (I did check
> that they are the right type and orientation I also check all the component
> values around Q18) Lets set that aside for just a second though...
> 
> Here is where I think it gets a little weird.  Looking at the schematic I
> followed it back to U4.  When I compared the voltage table to what i was
> actually seeing on U4 I think I may have found my problem.  According to
> the table pin 7 should have 0 Volts but i'm showing 4.8!  It also shows
> that pin 13 should have 4 volts but I'm showing 0.  All other pins are
> normal and match the chart.
> 
> Following Pin 7 of U4 back to Pin 1 of U5 I see the same 4.8 volts.
> This is supposed to be a clock line so I'm confused where this sort of
> voltage would be comming from.
> 
> I'm still new to alot of this and this is by far the most complex kit I've
> taken on so any and all help will be appreciated!
> 
> Thanks and 73,
> Robert
> AD0TA
> 
> 
>