[Elecraft] no DDS VFO output/KX1

[Don Wilhelm]

Ron,

Welcome to the Elecraft reflector.

If your 'scope is capable of seeing a 50 MHz signal of 100 mV peak to 
peak amplitude, yes you should see a good 50 MHz signal from the 
oscillator Z2.
If you have no oscillator there, and you measure 2.7 volts in Z2 pin 4, 
you may have a bad oscillator - no oscillator, the DDS will not work.

If you put a short antenna on the oscillator (Z2 pin 3) you should be 
able to hear it in a receiver with its "antenna" located a short 
distance from the added antenna wire.

If you indeed do not have an oscillator signal, it is likely a warranty 
repair and you should contact support at elecraft.com to request an RSA.
But make sure the leads of the components mounted in the vicinity do not 
have solder bridges that is shorting something to ground or another 
signal line.  Such builder errors are not warranty repairs.

There is nothing in the "KXB3080 'shortcut' instructions that would 
interfere with the DDS signal.

If you doubt the capability of your scope, use an RF probe to look for 
the oscillator and/or DDS signal.  Measured on an RF Probe you should 
have at least 70 mV signal at U2 pin 19.
Check for a signal at pin 20 too - if you have a signal at pin 20, check 
your work for solder bridges and other errors - like wrong value 
components at L4, L5, C39, C51, and C52 - check especially C52 to be 
sure it is 22pF (220) and not the 220pF (221) capacitor, those marking 
are difficult to see.

73,
Don W3FPR

On 8/23/2014 6:50 PM, wa7bme at citlink.net wrote:
> Hello All:
> My first time to post to this list.
> I am building KX1 S/N 2825 and have progressed to page 43 Alignment and Test Part 2 with no problems.  I have completed tests through page 44-keyer.
> I have not been able to proceed to the Receiver Alignment section, page 45, because I can not discern any signal from the DDS VFO, so not able to hear any
> signals, on either 20m or 40m.
> My question is this: should I be able to see the VFO signal at pin 19 of U2?  I am using an old TEK 422 scope with 10 x probe.  I see nothing at pin 19 or at pin 3 of Z2 the 50 mhz clock.  At pin 3 of Z2, clock output, I measure gnd (with power off, of course).  I also measure gnd at pin 4 of Z2, but also see 2.7 vdc when the unit is powered up.  No VFO or MCLK signals are visible.  This is confusing(!)
>
> I’m kinda stymied at this point, and any suggestions are welcome!
> Should I be able to hear the VFO signal on an outboard receiver?
> Should I be able to see the VFO signal at some point, and where is the best measurement point?
> Another note: I am using the directions from Don Wilhelm’s letter of 4 May, 2011 regarding replacement of components for KXB3080 option prior to installing the option.  This includes C27,C26,C1,T2. He will know what I am referring to.
> Sorry to run on for so long.
>
> Any help or suggestions, please?
>
>