[heathkit] drifting and jumping and chirping etc;;;;;;

[G3OOU@aol.com]

Hi Alan

 

1. Does the grid current variation also happen when using crystal control or only with the VFO?

 

2. I have the DX60 circuit to hand plus that of the DX60B - not much difference in the RF side.

 

3. The frequency variation could be because the problem is in the VFO or because the loading on the VFO is changing. If this happens in "spot" mode as well then it is probably not due to RF from the PA leaking into a sensitive circuit.

 

4. Have you tried gently rocking the two 6CL6 valves in their sockets while listening to the Tx note in a local Rx?

 

5. Check for corrosion on all chassis connections and any visible dry joints. Gently tap parts with a "rubber hammer" and see if the tone changes - something light and well insulated. IF that fails to find the problem then a freezer spray may be the bext best thing.

 

I have used grid block keying in early transmitters with a neon feeding the VFO control grid - worked well for me but the negative voltage must be high enough to strike the neon. I used -150v with an 85A2 or a VR105 to control the VFO and modified the Rx AGC to allow instant muting for full break-in. All homebrew.

 

Do some tests and let us know what happens.

 

73

Bob
G3OOU
G-QRP 6907
http://members.aol.com/rfcburns