Another Motorola VK-106 restoration attempt

[Electronic M]

Have you confirmed the DTV box RF signal quality with a different analog TV? Some cheap RF modulators (like those built into most home video sources) suck. Have you tried the set with a different modulator?...Sometimes a set happens to not like a specific modulator despite the modulator working with other sets...RF can behave like black majick sometimes.

Have you cleaned the tuner contacts, and tested the tubes in the tuner and IF? If the set has AGC have you adjusted it and verified it's operation? Is the internal tuner balun (usually mounted outside or inside the tuner box and linking the ant lead to the first tuner tube) still good?....Lightning killed a lot of tuner baluns back in the day.

Do you have a B&K 1075/76/77 series analyst? Those can modulate and inject IF carrier into the IF strip. Doing test injection with such a tool can id dead tuners and IF stages.

Have you compared socket voltages in the tuner and IF to those listed in the service literature?...If a stage has a major defect it should show up in the voltages.

These are all the easy steps to fix it or get you chasing a likely source of the problem....Beyond this lies the dark art of alignment, and or the engineering art of video injection.