[ARC5] power supply hum

[Kenneth G. Gordon]

On 23 Jan 2015 at 8:12, Leslie Smith wrote:

>   DS suggested I look at the tuning gang, and I intend to return to this
>   area.

It could be that the plates are not centered, or there is a bent plate, that is 
shorting the cap when it reaches a certain point.

>   The LO works when the tuning is set to around 200kHz.
>   The LO stops working when I tune the set above 270 .. 280 kHz.
>   I put the CRO on the oscillator plate lead.  ( see 15 to 20 volts RMS)
> 
> I put the CRO on the oscillator grid (triode section, pin #5).
> I see nothing.

That would not surprise me. Unless you are using a very high-impedance 
probe, or an RF probe, you will be shorting out anything that "is" on the grid.

Ken W7EKB