When the 3.58 craps out on most tube RCA's it gives you a
pink & green pix. Not sure if this applies to the -15. Its distinctive
when you see it. Dont remember the layout but its best
to get at least one known good 6GH8 & sub it once at a time.
Do not move them around it will cause confusion. 'GH8's
will work fine in one place but not in another...... Lots of
folk would bring in all the tubes for testing & when they put
them back in had different symptoms.
Not this but also watch for a short jumper wire at the
demod tubes that carried the filament voltage. Very common.
Its brown & dries up badly.
73 Zeno