[cathoderay57]

Hello all,
Some of you might have seen my earlier thread concerning the large elliptical "bass" speaker repair on a Graetz Sinfonia 4R AM/FM radio. Well I changed all the paper capacitors (yes every one) because they were all leaky on the Avo some measuring only a few kilohms. Powered it up and almost everything worked. It is a single-ended EL84 and certainly packs a punch. FM reception is excellent. Nothing needed tweaking apart from one new pilot lamp. However - the tweeter is not making any sound. Assuming I have not totally lost my high tone hearing I'd have thought I'd have picked up something with my ear right next to the tweeter. The "mid-range" is producing a reasonably high note which I can hear clearly. I know these capacitive tweeters (like the Grundigs) do tend to fail with age so I removed it from the baffle board. Externally it appears intact. I put it on my Avo Bridge and measured a capacitance of 45pF. Also when connecting it to the bridge there was some sound from it (a bit of scratching when connections were made and slight background buzz (maybe the smoothing on the Bridge PSU is getting past its best). However, installed in the radio it makes no sound. I have sketched the circuit (see attachment) because it differs from the output stage circuit shown on the Radio Museum schematic. The tweeter coupling capacitors 2.5nF and 50nF) have been replaced and the 5k and 10k resistors measure correctly. I don't have an AF signal generator so even if I put some HT on the tweeter I don't have a suitable signal source to inject into it. I'd have thought if the capacitive film inside had gone south it would measure o/c but it doesn't - as said 45pF. Anybody any ideas? I'm stumped for now. Cheers, Jerry