Motorola ts907 low hv

[Yamamaya42]

Unfortunately, this means that the IF is most likely badly out of alignment, most likely been tweaked.
Where as something like this MIGHT be caused by a bad component, if it was, it would more often than not be a faulty resistor than a bad capacitor, or even less likely a coil, cause as stated before, disc capacitors seldom ever go bad unless subjected to physical or electrical extremes, and since you have gone through and tested the resistors already, options are limited.

You may try to check all voltages on the pins of the IF tubes to see if they match what is listed in the schematic and hope to find something drastically wrong, but failing that there is not much else to do, other than hope to find someone with an alignment test setup, to debug/align the faulty stages, or bypass the RF/IF stage completely and go direct A/V input.