UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Superstar 6900N V6

SiriusHardware · 22nd May 2020, 10:46 pm

The switching checks look good so far, although there are ever deeper layers we can still go into. However we don't want you to get too bored so, time to wield your scope again. This time I'll ask you to look at area E1-E4 on the same sheet, sheet 3.

First try looking at test point TP301, 'BFO FRQ'. You should find that there is a steady RF waveform there in all modes on TX, and on USB, LSB and CW modes in RX. The frequency of this waveform will be about 10.695MHz so it is comfortably within the range of your scope.

If all is well there, move to the collector of Q520 - this is the output from the SSB modulator. When you key the microphone you should now only see bursts of RF which coincide with audio spoken into the microphone, and if you still have the beep turned on you should see a burst of RF carrier with the same duration as the beep when you release the microphone key.

22nd May 2020, 10:46 pm	#41
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,560	Re: Superstar 6900N V6 - Fault with SSB mode The switching checks look good so far, although there are ever deeper layers we can still go into. However we don't want you to get too bored so, time to wield your scope again. This time I'll ask you to look at area E1-E4 on the same sheet, sheet 3. First try looking at test point TP301, 'BFO FRQ'. You should find that there is a steady RF waveform there in all modes on TX, and on USB, LSB and CW modes in RX. The frequency of this waveform will be about 10.695MHz so it is comfortably within the range of your scope. If all is well there, move to the collector of Q520 - this is the output from the SSB modulator. When you key the microphone you should now only see bursts of RF which coincide with audio spoken into the microphone, and if you still have the beep turned on you should see a burst of RF carrier with the same duration as the beep when you release the microphone key.