COLIN LAMB wrote:

Is this hum on am or both am and cw. If it is only on am, then it would be
int he audio chain and not the power supply.

Colin K7FM




No ripple on the audio power buss [400+ vdc. 0.001 vac] This bus has a RC
filter of 20K and 20 uf. It is clean.

It is in both the AM & CW mode. So, it has to be the rf string where the +600 is
common to the two 6CL6s [series connected] and the 6146. I'm beginning to
suspect heater/cathode coupling/short in one or more of those tubes.

I gave my scope away about 5 years ago ... :-(

I have an EE degree and 40+ years of design/management experience, so a little
trouble shooting is not a problem for me. But, I have no capability to measure
capacitor ESR.

Well, I'll keep playing.

Thanks for suggestions.

DD, W1MCE