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Heathkit meter repair





My Heathkit DX-60B



The keying on a stock DX-60 is far too hard. I added some components to modify keying to normal rise and fall times.

This is the waveform of a stock DX60 (not B) on crystal control. On VFO it is even worse! The Delta-T shows 8.2 ms rise, but it's MUCH too sharp at the starting edge, at the rollovers, and at the drop. This rig is terrible for clicks.   



The mods are shown here...


Additional DX-60 audio modifications were:

C31 and C34 from .005 to .022uF

C35 from .1uF to 3.3uF

A series combination of a 2.2 Meg ohm and 500pF from pin 9 of the 6DE7 to pin 7   

Screen output dropping resistor R27 was decreased to 27K 2W

Note that while some modifications suggest making R27 variable, the audio distortion and percentage of modulation before clipping change with values of R27. I used an envelope distortion test to optimize R27. I have serious doubts anyone else can run the screen voltage all over the place without similar problems.

HG-10 Heathkit VFO

Works good as is.






A VF-1 with homebrew supply. Doesn't work so hot because no buffering, so I changed it to a triode oscillator followed by a pentode buffer. 


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