UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Help with FRG-7700 tuning problem needed

Jon_G4MDC · 13th Jan 2021, 3:11 pm

While that is a known problem it would be wrong to assume that is the reason on 4 VCOs.

The next best thing to do is to measure DC Voltage at TP03 on the PLL Unit. This is the tuning control Voltage for all VCOs. What is happening there will be a clue to the problem. Does it tune smoothly in step with VFO tuning? Is it stuck high or low? etc.

If the behaviour of TP03 is normal then this is probably a problem with the 47.6MHz Osc, the mixer or the counter.

13th Jan 2021, 3:11 pm	#8
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: Help with FRG-7700 tuning problem needed While that is a known problem it would be wrong to assume that is the reason on 4 VCOs. The next best thing to do is to measure DC Voltage at TP03 on the PLL Unit. This is the tuning control Voltage for all VCOs. What is happening there will be a clue to the problem. Does it tune smoothly in step with VFO tuning? Is it stuck high or low? etc. If the behaviour of TP03 is normal then this is probably a problem with the 47.6MHz Osc, the mixer or the counter. Last edited by Jon_G4MDC; 13th Jan 2021 at 3:29 pm.