Those sets were heavily SMD'd. Trapizoid raster was a common
problem on the Sonys & Zeniths BUT I never knew what it
was. We had the customers send them to Sony & the Zeniths
we took to the Zenith distributor.
My guess is under the circumstances...........
1) data in an e-prom corrupted
2) a dead supply.
good luck
Zeno
LFOD !
BTW measure twice, cut once !