DX-60 oscillator circuit

[Brian Carling]

Thnaks Ken - I will try that. I think part of the problem was that I 
had the "DRIVE TUNE" control mis-adjusted.
When I went back and retuned that control using the GRID 
CURRENT of the final to peak it, then the keying improved 
considerably.
I just don't like an oscillator to be slow to kick in.

I measure the screen grid resistor as almost 18,000 ohms.
It should be 15,000 ohms. I will need to the go get an RFC to 
measure screen voltage. 

I have just removed the erroneous "33 ohm resistor" (actually 37 
ohms) that was in the place of the 33,000 ohm resistor at R26
and realized I had mis-read the 100 uuFD as 100 uF and thought it 
missing! That was just a 33 pF disk and it IS there.


On 30 Dec 2005 at 20:23, Kenneth G. Gordon wrote:

> I just took a look at the schematic for the DX-60s oscillator and buffer 
> stages.
> 
> C-2, a 100 pfd capacitor, is connected between the oscillator tube and 
> ground...or at least it SHOULD be. You might want to mess with the 
> value of that cap a bit. This capacitor adjusts feedback to the oscillator.
> 
> However, FIRST I would measure the voltage at the screen of the 
> oscillator tube at key down. Connect an RF choke between the screen 
> connection and the DVM probe to keep RF from getting into the DVM 
> and causing erroneous readings.
> 
> If the voltage isn't at least 140 VDC or so, check the screen dropping 
> resistor. It is probably high in that case.
> 
> Ken W7EKB
> 

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