UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - PIN diode band switching yaesu ft-767

kellys_eye · 13th Feb 2021, 11:03 pm

Q31-Q39 are used to apply a DC bias to the filter diodes forward biasing them and allowing the signal to pass through the relevant L-C filter.

Check for the relevant DC levels on the transistor collectors and that it reaches the relevant filter.

The diodes can be checked in-situ with a standard test meter (assuming it has a diode tst function) and should read around 0.2V or 'infinite' depending on polarity.

13th Feb 2021, 11:03 pm	#2
kellys_eye Octode Join Date: Jan 2014 Location: Oban, Scotland, UK. Posts: 1,129	Re: PIN diode band switching yaesu ft-767 Q31-Q39 are used to apply a DC bias to the filter diodes forward biasing them and allowing the signal to pass through the relevant L-C filter. Check for the relevant DC levels on the transistor collectors and that it reaches the relevant filter. The diodes can be checked in-situ with a standard test meter (assuming it has a diode tst function) and should read around 0.2V or 'infinite' depending on polarity.