[Heathkit] HW-16 L-9 Value

[k2cby at optonline.net]

Mark,

I strongly suspect that you are getting output using the VFO with both tube
shields off because the driver is going into self-oscillation at some
unknown frequency independent of the VFO. 

I assume you've measured the key-down dc voltages on V7, V8 & V9 with a 40M
crystal plugged in and that they are within 10 or 15% of what the schematic
shows. If not, you should do so and troubleshoot as necessary.

Have you peaked L8 per the left-hand column on page 41 of the instructions?
It should resonate somewhere in the 40 Meter band.

One thing in the schematic struck me as strange. The VFO input socket makes
a dc connection to the control grid of V7. If there is dc (or a ground
return) at the output of whatever FVO you are using (or if any coupling
capacitor is leaky or shorted) it is going to kill the V7 grid bias. Along
the same line, you don't want to use a long run of coax from the VFO to the
xmtr because of attenuation.  

I assume both sets of measurements shown on your most recent post were made
with all tube shields in place. I also assume you used a 10X probe so the
scope isn't loading the measurements and the scope and the probe have a more
or less flat response to at least 21 MHz.

Last - but hardly least - I certainly assume you've replaced both 6CL6's
with known good tubes. (By the way, the best one should go in V8, which does
the "heavy lifting" as a tripler.)

That's about all I can think of at the moment.
We've got a mandate to "shelter in place" so I'm lurking on the internet a
lot more than usual.

73, Miles

 

Miles B. Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, New York 11963-3821
Phone: (631) 725-4400
FAX: (631) 725-2223

e-mail: k2cby at optimum.net