Congrats on your Avanti. That is the best chassis ever built by anyone.First thing is you MUST MUST check the HV caps. IIRC there are 2 on the flyback
& 3 more under the chassis. They are marked 22-5001 & all the same.
If they are white you MUST change them before anything else. If they
are orange they are OK to leave in. You must use the right type for
replacements or they WILL short out.
After thats done you can trouble shoot it. Its very easy to repair at that point.
To access under chassis there are 2 ways.
1) carefully flip set on its side & remove bottom plate.
2) Remove 4 heavy bolts from bottom of chassis. Place a heavy box behind
the set at chassis height. Loosen wire bundles & flip chassis on its side
on top of the box ( my favorite !).
I loved fixing these but even though we were a major Zenith dealer they
were bullet proof so didnt see many. If it werent for the HV cap problem
they were near 100% reliable for ever. CRT's also as good as you could get.
Never saw a weak one in the olden days.
73 Zeno
LFOD !