The culprit is the PS7 connector which brings mains voltage in your radio including hum you won’t get rid of.?

So it is not the PSU itself that brings the hum in your radio.?

I use a little relay box to switch on my PS7.?

So leave your electrolytics, just get the mains out of your radio and you‘re done.?

73 de Dieter DL5RDO

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Hi Jim,

After a lot of tests, PSU swaps, etc... I came to the conclusion that this TR7 is VERY VERY sensitive to any noise, AC spurs, hum that are present on the 13,5V supply voltage.

Even is powered with a external PSU but leaving the PS7 control connector connected, there is a hum on the signals.

All signals (RF, audio) are affected with these noises, sometimes it is very noticeable on the receiver audio.

The scope on the loudspeaker shows that on the 50 Hz main is wobbling the AF signals.

Even with a "clean" PS7 output, it is noticeable.?

The first thing I'm thinking about is the VCO board. I will order all caps and change them.

Has anyone already treated this problem ?

Thanks and 73,
Patrick

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