Recapped Sansui AU-719 Protection mode help!

If the issue changed sides then the problem lies in the pre-amp section. Will have a look at schematics.
Edit---

Nothing transistor related jumps off the schematic at me as a problem child so lets try this. Use tape 1 as input, tone controls and filters off, see if it mis-behaves. If it does try tapping on the protection relay and see if the sound returns. This is where a scope would really help as it allows us to 'see' fluctuations in signal level from board to board. If no results from this series of tests and in absence of a scope the next step will involve pulling first the tone board and then the eq board but I get ahead of myself.
Thanks for the suggestion, I've been listening all day and it seems to be behaving and sounding sweet, there was however briefly what sounded like mobile phone interference in the right channel which is very unusual. I'll keep my trusty chopstick at bay when the time comes and post the results.

Also just an unrelated question, in your experience do AU-719's tend to smell? It always has, I had just got used to it over the years, after using the 8080 quite a lot recently I'm noticing that it's just the 719 that does it. Kinda musky and old once it has warmed up, not like burning smell at all. I think it must be the different output transistors or circuit board material used.
 
Minor update, I've been using the amp all week and can't get the issue to reproduce, I was getting some intermittent mobile phone interference in the right channel.
I've since replaced the reversed cap on the phono board, replaced the two Bias trim pots, reset the Bias, DC Offset and phono equalizer pots and thoroughly cleaned the pin connectors and it seems to be it'sold reliable self again. *knock on wood*
Setting the phono equalizer setting couldn't have been a bigger pain in the ass! Literally tapping on the side of the pot with a long skinny screwdriver was the best I could do, I somehow managed to get it (by chance) 1mV off 0 too. it was way out of spec to start with.
The smell even seems to have diminished too, I think I may have adjusted set the Bias to Ohms not mV so it was running hotter than it should have, the also think the channel fading was due to an improperly connected plug but that's just my best guess. I'll keep on using it and report back if anything goes wrong. (again)
Thanks again everyone for the invaluable advice, let's hope this amp won't need much more of it.
 
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