Re: TR7 low band TX oscillation
¿ªÔÆÌåÓýSo¡buying a PS7 to replace my PS75 was a mistake? ? joseph n. graif k4jng ? -----Original Message----- ? ? This is a thing. Unfortunately not one of Drake's best ideas. I have seen at least one case where the owner added a toggle switch to the front of the PS7 and eliminated the mains feed through the TR7. To make this complete you need to use a DC fan in place of the FA7. ? A less drastic solution that I have considered is adding a low voltage circuit to the PS7 to sense the TR7 power switch and turn on mains power to that big transformer with a relay. ? 73 ? -Jim NU0C ? On Tue, 28 Nov 2023 13:55:05 +0100 "Dieter Horst" <dieter.horst@...> wrote: ? > Hi Patrick, > 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 > > > Von meinem iPhone gesendet > > Am 28.11.2023 um 07:00 schrieb Patrick TK5EP <pegloff@...>: > > > > ? > > > > 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 > > > > > > ? > > > ? ? ? ? ? |
Joseph K4JNG