A Front End

In any tuner, the first part is the front end. The Scott had sustained water damage and the front end board had some rust on it. I had to take it off and clean it first. Initially the plan was to use a new copper clad PCB and use point to point wiring but I decided to use the old board instead.

First I built the mixer and oscillator. The whole section is based on a Philips VHF TV tuner as used in the first more or less commercialy available color TV, the K4. I took off the FL516U module PCB and removed all components except the coils. The coupling winding on the second coil LR1 was removed and replaced by a top coupling capacitor. The IF transformer, built with two tuned coils was replaced with a single tuned coil transformer. Most capacitors are high voltage parts except when not needed.

After lots of tweaking and cursing I had a more or less acceptable 16 dB conversion gain. It should have been more, I had expected more than 20 dB. Maybe I'll investigate some time. If I feel like it...


chassis1

chassis2

fl516u_1

fl516u_2

fl516u_3

frontend_pcb1

frontend_pcb2

frontend_sch

front_view

filaments

if_out1

if_out2

if_mixer

mixer_osc

preamp1

preamp2

rear_view

side_view1

side_view2

top_view

mounted

mounted2

psu

psu_brd


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21 October 2015