Leave the filter bypassed and we'll proceed. It would be great if you had an FM signal generator so we could be looking at a sine wave instead of random audio. Down the road you might want to think about getting an FM modulator for use in a car, and a cheap audio oscillator. You power the modulator with a 12V supply, hook up your oscillator to the input and, presto, you have a cheap stereo FM signal generator. Synthesized, even! To proceed, what voltage do you measure on the bases of TR19 and TR20? They are tied together so just measure one of them. If you have .6V or above, the problem is in the mute circuit. If you adjust VR03 to one end or the other you should get audio. If so, remove the bypass on the filter and see how it sounds. I have a recording gig tomorrow and Sunday so I may not get back to this right away, but this gives you something to do. I just looked back to the beginning where you said you had both channels before the recap, but that may be related to this. Check the polarity and solder bridges at C48, C56, C57, C58. If all that is ok, and you got sound by adjusting VR03, you can try adjusting VR03 so it mutes on distant very noisy stations. If that makes it mute all the time again, then T06 and T07 need to be adjusted. You can try putting it on a strong station and adjusting T06 and T07 for the lowest DC voltage at the collector of TR13. Then do it again on a weaker station.