UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Yaesu FT-950 power drop and no low frequency output

SiriusHardware · 18th Feb 2021, 1:35 am

Do you have a link to a diagram? I think you need to know whether the set controls the power output by varying the PA stage supply voltage or by changing the size of the RF signal being passed to the input of the PA stage.

If it's an all-mode set then presumably the PA stage is linear - although you say the power declines whether the TX is used or not, maybe there is a problem with the biasing which may well be constantly applied whether the unit is in TX mode or not.

The lack of TX below 7MHz may be a different problem altogether.

18th Feb 2021, 1:35 am	#2
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,560	Re: Yaesu FT-950 power drop and no low frequency output Do you have a link to a diagram? I think you need to know whether the set controls the power output by varying the PA stage supply voltage or by changing the size of the RF signal being passed to the input of the PA stage. If it's an all-mode set then presumably the PA stage is linear - although you say the power declines whether the TX is used or not, maybe there is a problem with the biasing which may well be constantly applied whether the unit is in TX mode or not. The lack of TX below 7MHz may be a different problem altogether.